Topics

Can a Battery Be Used to Store Energy?

Friday November 4, 2011

A battery is a device that produces electrical energy from a chemical reaction. Another name for a battery is voltaic cell. Voltaic means to make electricity.

Most batteries contain two or more different chemical substances. The different chemical substances are usually separated from each other by a barrier. One side of the barrier is the positive terminal of the battery and the other side of the barrier is the negative terminal. When the positive and negative terminals of a battery are connected to a circuit, a chemical reaction takes place between the two different chemical substances that produces a flow of electrons (electricity).

When a battery is producing electricity, one of the chemical substances in the battery loses electrons. These electrons are then gained by the other chemical substance.

A battery is designed so that the electrons lost by one chemical substance are made to flow through a circuit, such as a flashlight lamp, before being gained by the other chemical substance. A battery will produce a flow of electrons until all of the chemical substances involved in the chemical reaction are completely used.

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Materials

Earphone or headset for a portable radio
Small piece of aluminum foil
Tomato paste or tomato ketchup
New, shiny penny
Two wires with alligator clips on each end of the wires
Plate
AA-size battery
Spoon

Download Student Worksheet & Exercises

Procedure

Examine the metal shaft of the part of the earphone or headset that is inserted into a portable radio. You will notice that just below the tip of the shaft there is a plastic spacer. Clip on one of the wires below this spacer. Then clip on the other wire above this spacer.

To test that the wires are properly connected to the earphone or headset, take the unconnected ends of the two wires and touch them to an AA-size battery. One wire should touch the positive end of the battery, while the other is touching the negative end of the battery. Place the earphone or headset to your ear. If your connections are made correctly, you should hear a crackling sound in the earphone or headset. If you do not hear a crackling sound, check your connections carefully.

Place a small piece of aluminum foil, about five inches (13 centimeters) square, on a small plate. Using a spoon, make a puddle of tomato juice on the aluminum foil. The puddle of tomato juice should be slightly larger than a penny. Next, place a new, shiny penny face down in the puddle of tomato juice.

Using the alligator clip, attach one of the wires connected to the earphone to one of the edges of the aluminum foil. Take the end of the other wire and touch the alligator clip to the penny. Move the alligator clip over the penny.

Observations

Do you hear a crackling sound when you touch the alligator clips to the penny in the puddle of tomato juice? What do you hear when you move the alligator clip over the penny? What do you hear when you stop touching the penny with the alligator clip?

Discussion

In this experiment you made a simple battery with a penny, aluminum foil, and tomato juice. You completed a circuit with your battery by touching one of the wires attached to the earphone or headset to the penny, while touching the other wire to the aluminum foil. When you completed the circuit, a flow of electrons was produced by your battery. The crackling sound you heard was caused by the earphone or headset converting electrical energy from your battery into sound energy.

In your battery, the aluminum in the aluminum foil loses electrons. The other part of the reaction is more complex. Either the acid in the tomato juice or copper ions (that form when the copper metal in the penny reacts with the acid in the tomato juice) gain the electrons lost by the aluminum.

The main types of batteries are known as primary and secondary batteries. Dry cell batteries, like the ones used in flashlights and portable radios, are primary batteries. Another important primary battery is the mercury battery. Mercury batteries are typically small and flat. They are used to power cameras, watches, hearing aids, and calculators.

An advantage of primary batteries is that they are generally inexpensive. One disadvantage is that they cannot be recharged. When the chemical substances in the primary batteries are used up, the battery is dead.

Lead storage batteries and nickel-cadmium (NiCad) batteries are examples of secondary batteries. Car batteries are lead storage batteries. Flashlight batteries that are rechargeable are NiCad batteries. Secondary batteries are more expensive than primary batteries. However, unlike primary batteries, lead storage batteries and NiCad batteries can be recharged repeatedly.

Other Things to Try

Repeat this experiment using other coins such as a dime, nickel, or quarter. Do any of these coins cause a louder crackling sound in the earphone or headset?

Repeat this experiment using a nail instead of a coin. Can you make a battery with other juices? To find out, repeat this experiment with other juices such as lemon and orange juice. What do you observe?

Exercises

Fill in the blank: A battery produces ___________________ energy from _________________________ energy.
Another name for a battery is:
1. Solar array
2. Voltaic cell
3. Nuclear reactor
4. Fusion cell
As one chemical loses electrons, what happens to the other chemical?
1. It loses electrons
2. It gains electrons
3. Nothing
4. It decomposes
When will a battery run out?
1. When its batteries run out
2. When its chemicals are used up
3. When all the electrons are gone
4. When the bunny stops drumming

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Can Insulation Save Energy?

Friday November 4, 2011

An insulator is a substance that partly blocks or slows the flow of heat through it. Styrofoam is a lightweight plastic used in drinking cups. Styrofoam is a good insulator. A cooler or ice chest that is made of Styrofoam or some other insulator tends to block the flow of heat through it.

Heat flows into buildings during warm summer months and from buildings during cold winter months. Energy must be used to cool buildings in the summer and heat them in the winter. Since insulation can slow the flow of heat, the use of insulation in buildings can save energy.

Some common home and building insulation materials include Styrofoam, polyurethane foam, and fiberglass. These materials are all good insulators, which means that they are poor conductors of heat. Placing these insulating materials on attic floors or in building walls tends to trap heat inside during the cold winter and keep heat out during the hot summer.

Plastic foams filled with trapped gas tend to block heat flow. The chemicals used to make polyurethane foam can be sprayed directly into the spaces between walls. These chemicals produce carbon dioxide gas and polyurethane plastic. The gas tends to spread the polymer apart so the weight is mostly plastic but the volume is mostly trapped gas. Polyurethane also is used to insulate refrigerators, refrigerated trucks, pipes, and building walls.

Fiberglass insulation is frequently used in attic floors to insulate homes. Also, fiberglass insulation is used to insulate the Trans-Alaska pipeline. This pipe carries oil 800 miles from Prudhoe Bay in northern Alaska to Valdez in southern Alaska. The crude oil that travels through this pipe is easier to pump if it is hot. An insulated pipeline requires less energy to keep the oil hot.

Energy conservation becomes more and more important as energy costs rise. A great deal of energy is used to cool buildings in summer and heat buildings in winter. Less energy will be needed if buildings are well insulated and energy is not wasted.
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Materials

Two large, plastic cups
Small, insulated ice chest or cooler (Styrofoam or plastic)
Ice
Watch or clock

Procedure

Completely fill each plastic cup with ice. Set one plastic cup out in the room. Set the other plastic cup of ice inside the small ice chest or cooler. Close the lid of the ice chest and leave both cups undisturbed.

Observe the cup of ice left out in the room once every hour. When all the ice has changed to water in the cup left out in the room, open the smaller cooler and observe the cup of ice inside. Continue to check on the cup of ice in the cooler about once an hour and see how long it takes to melt.

Observations

How long does it take for the cup of ice in the room to melt and change to water? When all the ice has melted in the cup in the room, is there still ice in the cup in the ice chest? How long does it take for the ice in the cooler to melt?

Discussion

You should find that the ice in the room melts faster than the ice inside the ice chest. When the ice in the room has all melted and only water remains, the cup inside the insulated cooler may still be mostly ice. Even though both cups were filled with the same amount of ice, they did not melt at the same time.

The temperature in the room is much warmer than the temperature of the cold ice. Since heat always flows from a higher temperature to a lower temperature, the heat in the room flows or moves into the ice and causes it to melt.

Other Things to Try

Repeat this experiment with a larger amount of ice, and you may see a greater difference between insulated and uninsulated containers. Try filling a bucket and an ice chest with equal amounts of ice, and set both containers outside on a warm day. How long does it take the ice in the bucket to melt? How long does it take the ice in the ice chest to melt?

You can reverse the experiment by comparing the flow of heat from the inside of a cup to colder surroundings. Use hot water from a sink faucet to partially fill a Styrofoam cup and a glass cup. Place the Styrofoam cup inside two other Styrofoam cups and cover the top with several layers of aluminum foil. Next place the Styrofoam cups and the glass cup inside the refrigerator and compare how long it takes for the water to cool.

Fill a thermos bottle with hot water. Wait about four hours and check the temperature of the water. Continue to check the temperature about every two hours to find out how long the thermos bottle can keep the water warm. A thermos bottle has glass walls with a vacuum between them and silvered surfaces to reflect heat. The vacuum in a thermos makes an excellent insulator because there are few gas molecules to transfer heat.
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Can a Salt Be Used for Heating and Cooling?

Friday November 4, 2011

Cooling and heating are opposite processes. Cooling is the removal of heat energy from an object or space and heating is the addition of heat energy to an object or space. We use these opposite processes a great deal in our daily lives. For example, in the kitchen we use the cooling provided by a refrigerator to keep food cold. We also use the heat from a stove to cook food.

Nearly 75 percent of the energy used by the average family household in the United States goes for cooling and heating purposes. Air conditioning and refrigeration are the major cooling requirements of a home, while water and space heating are the most important heating requirements.

In the experiments that follow you will learn more about cooling and heating. You will also learn alternative ways of cooling and heating, using such unusual materials as gases, salts, water, and trees.
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Materials

Epsom salt
Aluminum pie pan
Water
Oven
Insulated mitt
Two small, zipper-close, plastic bags
Sink
Measuring cups

Procedure

ASK AN ADULT TO HELP YOU WITH THIS EXPERIMENT. DO NOT USE THE STOVE BY YOURSELF.

Ask an adult to turn on the oven and to set the temperature of the oven to 450° F

(232°C). Pour one-half cup of Epsom salt into an aluminum pie pan and gently shake it to evenly spread the Epsom salt over the bottom of the pan. Place the pie pan in the oven. Heat the Epsom salt in the hot oven for thirty minutes.

Ask an adult to remove the pan of Epsom salt from the hot oven using an insulated mitt. Place the pan on the stovetop and allow it to cool for ten minutes. Make sure the oven is turned off.

Add one-quarter cup of the Epsom salt that was not heated in the oven to a small plastic zipper-close bag. Next add one-quarter cup of room temperature water to the bag, seal, and shake the bag. Feel the temperature of the outside of the bag.

Next add one-quarter cup of the cooled Epsom salt that was heated in the oven to the second zipper-close bag. Add one-quarter cup of room temperature water to the bag and seal the bag. Give the bag a couple of shakes and then feel the outside of the bag.

When you are finished with this experiment, pour the contents of both bags down a sink drain. Then flush the bags and the sink with water. Also rinse out the aluminum pie pan with water. DO NOT DRINK ANY OF THE LIQUID AND DO NOT EAT ANY OF THE EPSOM SALT. EPSOM SALT CAN MAKE YOU SICK IF YOU EAT IT.

Observations

Do you notice any difference in the appearance of the Epsom salt after it is heated in the oven? Does the bag containing the water and the Epsom salt that was not heated feel warm or cool after shaking? Does the bag containing the water and the Epsom salt that was heated feel warm or cool after shaking?

Discussion

Epsom salt is a hydrate of the salt called magnesium sulfate. A hydrate is a chemical substance containing water combined with another chemical substance (usually a salt). The water molecules in a hydrate are called waters of hydration. They can usually be removed from the hydrate by heating. The process of removing water from a hydrate is called dehydration.

In this experiment, when you heated the Epsom salt in the oven, you removed most of the water molecules (waters of hydration) in the salt.

A salt is made of positive and negative ions. Ions are charged atoms or groups of atoms. In Epsom salt, magnesium ions are positive and sulfate ions are negative. The waters of hydration surround these ions in Epsom salt.

You should find that the bag containing water and the dehydrated Epsom salt feels warm. The bag containing water and the hydrated Epsom salt feels cool. When dehydrated Epsom salt is mixed with water, heat is given off. When hydrated Epsom salt is mixed with water, heat is absorbed. When something gives off heat it feels warm, while something that absorbs heat feels cool.

Energy is required to remove individual ions from a salt crystal. However, energy is given off when the individual ions that break away from the crystal become surrounded by water molecules that are dissolving the salt. If more energy is required to remove individual ions from a salt crystal than is given off when the ions become surrounded by water, then the salt solution becomes cold. If more energy is given off when the ions become surrounded by water than is needed to remove individual ions from a salt crystal, then the salt solution becomes warm.

When hydrated Epsom salt dissolves in water, more energy is required to remove the magnesium and sulfate ions (and the waters of hydration) from the crystals than is given off when the magnesium and sulfate ions become surrounded by the dissolving water molecules.

This is why the bag containing the unheated Epsom salt became cold when you added water.

On the other hand, when dehydrated Epsom salt dissolves in water, more energy is given off by the ions becoming surrounded by water molecules than is needed to break the magnesium and sulfate ions from the crystals. This is why the bag containing the dehydrated Epsom salt became warm when you added water.

Most instant hot packs and cold packs that are available in drugstores work on the principle just discussed. When the cold or hot pack is needed, the bag is squeezed to cause the water and salt to mix. Depending on the salt used in the pack, energy is either absorbed (cold pack) or given off (hot pack). Ammonium nitrate is the most commonly used salt in cold packs. And calcium chloride is the most commonly used salt in hot packs.

Other Things to Try

Repeat this experiment using a thermometer to measure the temperature change when the Epsom salt is dissolved in water. Use the thermometer to measure the temperature change when dehydrated magnesium sulfate is dissolved in water.

Repeat this experiment using table salt. Do you observe a temperature change when the table salt dissolves in water?
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How Can Shade Trees Keep Things Cool?

Friday November 4, 2011

Having shade trees around a house can decrease the cost of cooling the house with air conditioning. A house not shaded from the sun absorbs some of the light from the sun and heats up the outside surface of the house. If the house is poorly insulated, some of this heat will penetrate into the house, heating up the inside. The air conditioner will use more energy to remove this added heat.

Properly designed roof overhangs can significantly decrease the heating and cooling costs of a house. Because the earth’s axis is tilted, the sun is lower in the winter in the northern hemisphere. In the summer, the sun is higher in the sky. A properly designed roof overhang allows sunlight in the winter to shine through windows and warm the furnishings in the rooms that receive the direct sunlight. This reduces the heating cost in the winter. In the summer, the overhang blocks the sunlight from shining into the window and heating the furnishings. This reduces the cooling cost in the summer.
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Materials

Two large, glass jars
Shady tree
Water
Thermometer (optional)

Procedure

You will want to do this experiment on a warm, sunny day. Fill both large, glass jars nearly full with water. Place one of the jars outdoors in a spot where sunlight will strike it for several hours. Place the other jar outdoors under a shady tree.

After three hours, feel the water in the jar that was left in the sun. Next feel the water in the jar kept under the shady tree. If you have a thermometer, check the temperature of the water in each jar. Also check the air temperature with the thermometer.

Observations

Does the water in the jar left in the sun feel warmer or cooler than the water in the jar left under the shady tree? If you are using a thermometer, what is the temperature of the air and of the water in each jar? What is the temperature difference of the water in the two jars?

Discussion

The water in the jar that was left in the sun should feel much warmer than the water in the jar left under the shady tree. The temperature difference of the water in the two jars will vary depending on the air temperature and wind conditions. On a hot, sunny day you may find that the temperature of the water in the jar left in the sun is over 18° F (10° C) warmer than the air temperature and the temperature of the water in the jar kept in the shade.

The jar of water left in the sun is constantly bathed with light energy from the sun. Some of this light energy is absorbed by the glass jar and the water in the jar. The light energy that is absorbed by the glass jar and the water is converted into heat energy. This is why the jar of water becomes warm after being in the sun for several hours.

The tree shades the other jar of water from the sun. The jar of water under the tree does not absorb light energy directly from the sun as the other jar did. Instead, much of the light energy from the sun is absorbed and used by the tree.

Since the jar of water under the tree does not absorb light energy directly from the sun, it remains cooler than the jar of water kept in the sun. You may even find that the temperature of the water in the jar shaded from the sun is a few degrees cooler than the air temperature. This is caused by water evaporating from the jar. Heat energy is removed when a liquid evaporates, and the liquid becomes slightly cooler.

Other Things to Try

Repeat this experiment at different times of the day. Do you get similar results? Repeat this experiment when it is cloudy. How does the difference in the temperatures of the jars of water compare on sunny and cloudy days.
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Can the Evaporation of Water Be Used for Cooling?

Friday November 4, 2011

The evaporation of water for cooling purposes is called evaporative cooling. An important example of this type of cooling is the removal of body heat by humans through sweating. When your body needs to cool, perspiration is released to the surface of your skin where it evaporates. The evaporation of the water in the perspiration causes your skin to cool.

Breezes feel particularly cooling when you have perspiration on your skin. This is because the increased movement of air over your body evaporates more water from your skin than still air does. Water on your skin evaporates more slowly when the humidity is high. This is because the humid air already contains much water vapor. Humid air absorbs less water as vapor than dry air.

Electrical power plants that burn fossil fuels or use nuclear energy to generate electricity use huge water cooling towers for cooling purposes. The water to be cooled is pumped to the top of the tower and allowed to drip down through the tower. As the water moves down the tower, air from the bottom of the tower moves up through the tower, evaporating some of the falling water. The heat lost by the evaporating water cools the remaining water that is collected in a basin under the tower. One pound of water that evaporates in a tower can lower the temperature of 100 pounds (45 kilograms) of other water by nearly 50°C (100°F).
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Materials

Unglazed clay flower pot
Plastic bowl
Unglazed clay saucer
Water
Modeling clay
Thermometer (optional)

Procedure

Make sure to use an unglazed clay flowerpot for this experiment. Most unglazed clay flowerpots have an orange-red color and rough surfaces. The bottom of the unglazed clay saucer should have a diameter larger than the top diameter of the flowerpot. (Flowerpots and saucers can be purchased at most hardware and plant stores.)

Most clay flowerpots have drainage holes. Check to see if your clay flowerpot has a drainage hole in the bottom. If the one you are using has a hole, seal it with a piece of modeling clay. Add some water to the pot to make sure your seal is watertight.

Place the clay flowerpot and plastic bowl outside on a hot, sunny day and in a spot where they will get plenty of sunshine. Fill both the clay flowerpot and the plastic bowl nearly full with water. Place the clay saucer on top of the flowerpot and fill it with water.

Every hour for three hours, place your hands around the outside of the plastic bowl of water. Then place your hands around the outside of the clay pot filled with water. Next dip your hand into the plastic bowl of water. Remove the clay saucer from the flowerpot and dip your same hand into the pot of water. If you have a thermometer, place it in the plastic bowl of water. Read the temperature on the thermometer after it has been in the water thirty seconds. Next place the thermometer in the clay pot of water. After thirty seconds read the temperature of the water in the clay pot.

Observations

Does the outside of the clay flowerpot appear wet and feel wet after it has been outside several hours?

Does the outside of the plastic bowl feel warmer or cooler than the outside of the clay flowerpot after both containers have been in the sun several hours? Does the water in the clay flowerpot feel warmer or cooler than the water in the plastic bowl?

If you are using a thermometer, what is the temperature of the water in the plastic bowl? What is the temperature of the water in the clay pot?

Discussion

You should find that soon after you add the water to the unglazed clay flowerpot, the outside of the clay pot looks and feels wet. The outside of the clay flowerpot should feel cooler than the outside of the plastic bowl. Also, the water inside the flowerpot should feel much cooler than the water inside the plastic bowl. In fact, if you measured the temperatures of the water in both containers you may have found that the water in the clay pot was cooler by as much as 18°F (10°C). The temperature difference will depend on the air temperature, the humidity, and wind. The higher the humidity and the less wind there is, the smaller the temperature difference between the two containers will be.

The outside of the clay flowerpot becomes wet because water inside the flowerpot moves through the wall of the clay pot. When water reaches the outside surface of the clay pot, it can evaporate. When the water evaporates, it changes from a liquid to a gas or vapor.

Heat energy is required for water to evaporate. This heat energy comes from the clay pot and the water inside the clay pot. When the water evaporates and removes heat from both the pot and water, the temperature of both the pot and water decreases.

Water evaporates from the plastic bowl as well. However, since water cannot move through the plastic, water evaporates only from its surface in the plastic bowl. More heat is removed from the clay pot than the plastic bowl because water is evaporating from a larger area. This is why the outside of the clay pot and the water inside it should feel cooler than the outside of the plastic bowl and the water inside it.

Other Things to Try

Repeat this experiment and record the temperatures of the water in the two containers with a thermometer every hour for five or six hours. Is the temperature of the water in the clay pot always lower than the temperature of the water in the plastic bowl?

If you are ever near the bottom of a waterfall, notice that the air temperature around the waterfall is cooler than air away from the waterfall. Can you explain why?
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Can Expanding Gases Be Used for Cooling?

Friday November 4, 2011

In a typical air conditioning or refrigeration system, a liquid at high pressure is allowed to pass through a valve from a higher pressure to a lower pressure. As the liquid enters the lower pressure region, it changes from a liquid to a gas. This change causes a cooling effect. The liquid cools as it changes to a gas.

In a cooling system, such as a refrigerator or air conditioner, this cold gas is used to cool a box (refrigerator) or a room (air conditioner). Then the cool gas is forced through a compressor pump where it undergoes a warming effect and changes back to a liquid. This excess heat is removed before the liquid is expanded to a gas again. In an air conditioner, the excess heat is blown outside.

Special molecules containing chlorine, fluorine, and carbon atoms are used in most cooling systems. These Freon or chlorofluorocarbon (CFC) molecules are used because they are stable, nontoxic, and will not burn.

In recent years, scientists have discovered that these Freon or CFC molecules are damaging the earth’s ozone layer. Ozone molecules in the upper atmosphere block harmful ultraviolet radiation from reaching the earth. Because these CFC molecules are so stable they tend to stay in the atmosphere for many years, during which time they gradually spread to the upper atmosphere.

In the upper atmosphere, CFC molecules can release chlorine atoms. These atoms cause a chemical reaction that breaks apart ozone. One chlorofluorocarbon molecule may destroy thousands of ozone molecules. Scientists and engineers are looking for new methods of cooling and new gases that are less damaging to the ozone layer.

The main energy used in operating a cooling system is the energy required to run a compressor to force a gas to a higher pressure, where it will change back to a liquid. This energy is normally supplied by electricity or by burning natural gas to run a compressor pump. However, there are systems in which solar energy is used to supply the energy needed for cooling.
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Materials

Thermometer (outdoor type)
Newspaper
Can of Lysol® spray (use pressurized aerosol can, not pump spray)

Procedure

HAVE AN ADULT HELP YOU WITH THIS EXPERIMENT. LYSOL®, LIKE OTHER SPRAY CANS, SHOULD NOT GET NEAR A FLAME, AND THE CONTENTS SHOULD NOT GET IN YOUR EYES.

Set a can of Lysol® spray in the room where the experiment will be done and wait one hour. Observe the temperature of the room by reading the temperature on a thermometer. The can of Lysol® spray should be the same temperature as the room.

Place about ten sheets of newspaper, one on top of the other, on the floor. Have an adult hold the thermometer in one hand and the spray can in the other hand. These items should be held above the newspaper to catch Lysol® liquid that may drip off the thermometer. The adult should hold the nozzle of the Lysol spray can about four inches from the bottom of the thermometer. Have the adult spray the bottom of the thermometer for twenty seconds.

While the adult sprays the Lysol® on the thermometer, you should observe the temperature. After he or she stops spraying, continue to observe the temperature on the thermometer for several minutes.

Observations

What is the temperature of the room and the can of Lysol® spray? Does the temperature drop while the Lysol® is sprayed? What is the temperature while gas is sprayed from the can on the thermometer? What happens to the temperature after the spraying is stopped?

Discussion

You should find that the temperature on the thermometer drops as the Lysol® is sprayed on it. The temperature may decrease by 14° F (8° C) or more. After the spraying is stopped, the temperature may drift slightly lower, and then should gradually increase to the original temperature of the room.

If you shake the can of Lysol®, you should hear the sound of a liquid sloshing or moving inside the can. The can contains gas and liquid. When the can is sprayed, the pressurized gas escapes and liquid expands to a fine mist or vapor (gas). This change, from a higher pressure to a lower pressure gas and from a liquid to a gas, causes a cooling effect. You observe this cooling when you see the thermometer’s temperature decrease.

Other Things to Try

Open a two liter soft drink bottle that has been out in the room for several hours. As you open the bottle, let the carbon dioxide gas that escapes and causes a hissing sound fall on your lips. Does the gas coming out of the soft drink bottle feel hot or cold?
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Can the Sun Be Used to Heat Water?

Friday November 4, 2011

The energy of sunlight powers our biosphere (air, water, land, and life on the earth’s surface). About 50 percent of the solar energy striking the earth is converted to heat that warms our planet and drives the winds. About 30 percent of the solar energy is reflected directly back into space. The water cycle (evaporation of water followed by rain or snow) is powered by about 20 percent of the solar energy.

Some of the sunlight that reaches the earth is used by plants in photosynthesis. Plants containing chlorophyll use photosynthesis to change sunlight to energy. Since these green plants form the base of the food chain, all plants and animals depend on solar energy for their survival.

When the sun is overhead, about 1,000 watts of solar power strike 1 square meter (10.8 square feet) of the earth’s surface. Using solar cells, this solar energy can be converted to electricity. However, because sunlight cannot be converted completely to electricity, it takes at least a square meter of area to gather enough sunlight to run a 100-watt light bulb.

Solar energy is still more expensive than other methods of generating electricity. However, the cost of solar electricity has greatly decreased since the first solar cells were developed in 1954.

It has been proposed that panels of solar cells on satellites in orbit above the earth could convert solar energy to electricity twenty-four hours a day. These huge solar power satellites could convert electrical energy to microwaves and then beam these microwaves to Earth. At the earth’s surface, tremendous fields covered with antennas could convert the microwave energy back to electricity.

It would take thousands of astronauts many years to build such a complicated system. However, there are many practical uses of solar energy in use today. These uses include heating water, heating and cooling buildings, producing electricity from solar cells, and using rain and snow from the water cycle to power electrical generators at dams.

In the following experiments, you will examine the use of solar energy in heating water, .cooking foods, concentrating sunlight, and producing electricity.
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Materials

Paint brush
Thermometer (outdoor type)
Newspaper
Aluminum foil
Water
Large, plastic glass
Empty aluminum 12-ounce (355 milliliter) soft drink can
Black paint or spray paint (flat, not shiny)

Download Student Worksheet & Exercises

Procedure
Go outside and spread a sheet of newspaper on the ground. Place an empty aluminum soft drink can on the newspaper. Have an adult help you paint the outside of the aluminum can. You can use a brush and can of paint or spray paint. Be sure to use paint that is suitable for a metal surface. The paint should give you a flat (not shiny) surface. Be sure not to get the paint on anything but the can and newspaper. After painting, set the can where the paint can dry overnight.

You will need to do the rest of this experiment on a warm, sunny day. Partially fill a large, plastic glass with cool tap water. Check the temperature of the water with a thermometer. Pour the water from the plastic glass into the painted black can, completely filling the can. Pour out any extra water remaining in the plastic glass. Cover the can’s opening with a small piece of aluminum foil about the size of a quarter.

Set the black can outside in a sunny spot. Pick a place where the sun will shine on the can all day. (You do not want the can to be in the shade.)

After the can of water has been in the sunshine for about four hours, pour the water into the large, plastic glass. Check the temperature of the water with the thermometer. Feel the outside of the can.

Observations

What was the temperature of the cool tap water when it was first placed into the black can? What is the temperature of the water after it was heated in the can for four hours? Does the outside of the can feel hot?

Discussion

You should find a significant increase in the temperature of the water that was left in the black can during the day. The tap water initially may be about 21°C (70°F), but after the water has been heated inside the can, the temperature should rise to more than 38°C (100°F). The exact temperature you achieve in your miniature, solar water heater (black can) will depend on your location and the time of year. However, you should find that the water temperature will go much higher than the temperature of the outside air.

The electromagnetic radiation from the sun includes ultraviolet, visible, and infrared radiation. Ultraviolet radiation is the type of sunlight that causes tanning of skin. Visible radiation is the type of sunlight we see with our eyes. Infrared radiation is the type of sunlight that we feel as heat when the sun is shining on our skin. All these forms of solar radiation have energy associated with them.

When solar energy from the sun’s electromagnetic radiation strikes a black surface, solar energy is converted to heat energy and the surface is warmed. Other colors will absorb solar energy, but lightly colored surfaces tend to reflect the light, while darker colors absorb the solar energy. You may have noticed this difference if you ever walked barefoot on a dark road on a hot summer day.

Direct solar energy is not hot enough for cooking. The higher temperatures required for cooking or for changing water to steam require concentrating the energy of sunlight with mirrors or lenses. However, directly absorbed solar energy is hot enough for heating homes and producing hot water with little or no energy costs.

When we turn on a hot water faucet at a sink, water is taken from a hot water tank. In industrialized countries, we usually heat water using electricity or natural gas and store the hot water in this insulated tank. However, around the world, there are millions of solar heaters used for heating water.

Solar water heaters use a black metal plate covered with insulated glass. These solar heaters are usually placed on rooftops to receive the maximum amount of sunlight. Water flows through tubes beneath the black metal plates. Solar energy heats the black metal plates and the water passing in tubes underneath the plates. The heated water is piped to a storage tank, where it is kept until needed. If the location of the solar heater is not consistently sunny, then an auxiliary heater-using electricity or natural gas-is sometimes used to heat the water.

Other Things to Try

Repeat this experiment covering the black can with a large glass jar. This glass should help trap the heat and make the water get even hotter. What is the maximum temperature you can get with this type of solar heater?

Repeat this experiment and check the temperature of the water each half hour for three hours during the middle of the day. Quickly check the temperature of the water, then return the water to the black metal can. Write down the time that you checked the water, and next to the time, write down the temperature. How long does it take for the water to reach the maximum water temperature?

Repeat this experiment with an unpainted can and a painted can. After one hour, how do the temperatures of the water in each can compare?

Repeat this experiment on a cloudy day. Does the water in the can get as hot without sunshine?

Exercises

The solar energy that hits the earth is responsible for what proportion of the energy on our planet?
1. Nearly all of it
2. About 50%
3. 25%
4. None of these
Name one way that the physical earth uses the earth’s energy:
True or false: Solar power is generally less expensive than other forms of power.
1. True
2. False

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How Can the Sun Be Used for Cooking?

Friday October 28, 2011

Cooking involves heating food to bring about chemical changes. Sometimes foods are heated simply because the food tastes better warm than cold. In making tea, we sometimes heat water to help dissolve tea or help dissolve sugar if the tea is sweetened.

Normally the water used to make tea is heated on a range top or in a microwave oven. Using a range or microwave oven requires buying energy in the form of electricity or natural gas. Using a solar cooker does not require any energy costs because it uses a freely available renewable energy source-the sun.

A curved mirror in a bowl-like shape can focus reflected sunlight at a spot for cooking. A mirror about 1.5 meters (5 feet) across can generate a temperature of 177°C (350°F) and boil a liter of water in about fifteen minutes. In sunny areas of the world, solar cookers can be used instead of burning firewood for cooking.

Another way reflected and focused sunlight is used is to generate electricity. In southern California in 1982, a solar-thermal plant was built that can generate ten million watts of electrical power. This plant consists of 1,818 mirrored heliostats. A heliostat is a device that moves to track the sun across the sky and to reflect the sunlight at the same point. Each heliostat has twelve mirrors, and all the heliostats reflect sunlight to the same spot. The reflected light is directed at the top of a 90-meter (295-foot) tall tower. The concentrated sunlight is used to boil water and heat the steam up to 560° C (1,040 ° F). The steam turns a turbine that powers a generator to produce electricity.

One obvious disadvantage of solar-thermal plants is that they only operate when the sun is shining. The heat energy can be stored for a time by heating up a liquid or melting salt. Or the energy can be used to break water into hydrogen and oxygen. The hydrogen can then be stored and burned later to produce water and release energy.
[am4show have=’p8;p9;p22;p49;p75;p84;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Materials

Three clear, clean plastic cups
Two small tea bags
Aluminum foil
Watch or clock
Measuring cup
Water
Two spoons
White sheet of paper
Plastic pan (4 inches deep and 12 inches across is a convenient size but other sizes can be used)

Download Student Worksheet & Exercises

Procedure

You will need to do this experiment on a warm, sunny day.

Use two sheets of aluminum foil and place them crosswise to completely cover the bottom and sides of a plastic pan. Try to arrange the aluminum foil so that it is smooth and curved like a bowl. The aluminum foil will help to reflect the solar energy and concentrate the light and heat toward the center of the pan. Place this aluminum covered pan outside in a warm, sunny spot where the sunlight will shine directly on it.

Add one cup of water to each of two plastic cups. The water you add to the cups should be neither hot nor cold, but about temperature. Place one cup of water in the middle of the pan. Turn the empty plastic cup upside down and place it on top of this cup. Leave this “solar cooker” undisturbed for one hour. The other cup of water should remain inside.

After one hour, gently place one tea bag in each of the water-filled cups. Wait ten minutes and then lift the tea bag out of each cup. Using a spoon, stir each cup of tea. Place both cups of tea on a white piece of paper and look down on the two cups to compare their darkness. Put your finger in each cup of tea to compare their temperatures.

Observations

Which cup of tea is a darker color? Which cup of tea is warmer?

Discussion

You should find that the water left in the “solar cooker” is darker and warmer than the water left in the shade. The darker color indicates that more tea has gone into or dissolved in the warmer water.

Other Things to Try

Place your “solar cooker” in the sun as in this experiment, but place one plastic cup upside down in the middle of the pan. Put a pat of margarine or butter on top of this cup. Will the sun melt this butter? How long does it take to melt? Repeat this activity with a piece of soft cheese and determine if the solar heater will melt the cheese. In a more carefully made solar cooker, the reflective surfaces are angled to focus a large amount of sunlight in one spot and the temperatures obtained are much higher than in your cooker.

Set one cup of water in your “solar cooker.” Set a second cup of water in the sunshine and leave both cups for one hour. Use a thermometer to check the temperature of each cup of water. Does your “solar cooker” help focus the sun’s rays and increase the temperature?

Exercises Answer the questions below:

What type of solar energy are we seeing in this experiment?
1. Solar fusion
2. Solar voltaic
3. Solar thermal
4. Radiation potential
Name two ways that the earth’s systems depend on the sun:
What is one advantage of solar thermal energy? What is one disadvantage?
1. Advantage:
2. Disadvantage:

Can Solar Energy Be Concentrated?

Friday October 28, 2011

The curved shape of the magnifying lens causes light rays to bend and focus on an image. When we look through the lens, we can use it to make writing or some other object appear larger. However, the magnifying lens can also be used to make something smaller. The light from the bulb is bent and focused on the wall when the lens is held far from the lamp and close to the wall. The image is much brighter than the surroundings. This is because all the light falling on the surface of the lens is concentrated into a much smaller area.

When sunlight is concentrated by passing it through a lens, the result can be an intensely bright and not spot of light. Even a small magnifying glass can increase the intensity of the sun enough to set wood and paper on fire. We are using a light bulb rather than sunlight for this experiment because concentrated sunlight Can be very harmful to your eyes. NEVER LOOK AT A CONCENTRATED IMAGE OF THE SUN.

The United States Department of Energy’s National Renewable Energy Laboratory in Colorado uses solar energy to operate a special furnace. This high-temperature solar furnace uses a lens to concentrate sunlight. A heliostat (a device used to track the motion of the sun across the sky) is used so that the image reflected from a mirror is always directed at the same spot. The lens is used to concentrate sunlight from a mirror to an area about the size of a penny. This concentrated sunlight has the energy of 20,000 suns shining in one spot.

In less than half a second, the temperature can be raised to 1,720° C (3,128° F) which is hot enough to melt sand. This high-temperature solar furnace is being used to harden steel and to make ceramic materials that must be heated to extremely high temperatures.

Concentrated sunlight also has been used to purify polluted ground water. The ultraviolet radiation in sunlight can break down organic pollutants into carbon dioxide, water, and harmless chlorine ions. This procedure has been successfully carried out at the Lawrence Livermore Laboratory in California. In the laboratory, up to 100,000 gallons of contaminated water could be treated in one day.
[am4show have=’p8;p9;p22;p49;p84;p85;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Materials

Lamp with a single incandescent bulb
Magnifying lens

Download Student Worksheet & Exercises

Procedure

The results of this experiment may be easiest to observe if done at night in a dark room.

Ask an adult to remove the lamp shade from a lamp that uses a single incandescent bulb. An incandescent bulb is the type that gets quite hot when used. Turn on the lamp. Turn off all the other lights in the room.

Stand about two feet from the wall that is the greatest distance from the lamp. There should be nothing between you and the lamp bulb. Place the magnifying glass on the wall so that the lens is flat against the wall. Now, slowly move the lens away from the wall and toward the light. Keep the lens parallel to the surface of the wall. As you move the lens outward, watch the wall.

Observations

Does an image of the lamp appear on the wall? How bright is this image? How big is this image?

Discussion

You should see an upside down image of the light bulb appear as you move the magnifying lens away from the wall. The image should be much brighter than the area around it and much smaller than the size of the real bulb. The image may be only about the size of your fingernail or smaller.

Other Things to Try

Trace the exact size and shape of the magnifying lens on a piece of paper. Cut out this piece of paper and tape in on the wall. Focus the image of the lamp on this piece of paper and copy the bulb image on the paper. Compare the size of the bulb image to the size of the piece of paper. How much bigger is the lens than the focused image of the bulb? Use this ratio of sizes to estimate the increase in the brightness of the image.

Can you explain why the image of the bulb is upside down when it is projected on the wall? See if you can find information about optics in a book or encyclopedia that could help you explain this reversal of the image.

Repeat this experiment using two magnifying lenses. Observe the effect of moving the positions of the two lenses relative to each other and the wall.

Exercises Answer the questions below:

Name three uses for solar energy:
What type of heat energy is transmitted by the sun?
1. Conduction
2. Convection
3. Plasma
4. Radiation
Circle the following phenomena influenced by the sun:
1. Pressure
2. Climate
3. Weather
4. Wind

[/am4show]

Can Electricity Be Made From Sunlight?

Friday October 28, 2011

The solar cell you are using for this experiment is made from the element silicon. Silicon solar cells consist of two thin wafers of treated silicon that are sandwiched together. The treated silicon is made by first melting extremely pure silicon in a special furnace. Tiny amounts of other elements are added which produce either a small positive or negative electrical charge.

Usually boron is added to produce a positive charge and phosphorus is added to produce a negative charge. The addition of these other elements to pure silicon to produce an electrical charge is called doping.

After being doped, the molten silicon is allowed to cool. As it cools, the doped silicon grows into a large crystal from which very thin wafers are cut. A wafer cut from a large crystal of silicon doped with boron is called the positive or P-layer because it has a positive charge. A wafer cut from a large crystal of silicon doped with phosphorous is called the negative or N-layer.

To make a solar cell, a positive wafer (P-layer) and a negative wafer (N-layer) are sandwiched together. This causes the P-layer to develop a slight positive charge, and the N-layer to develop a slight negative charge. The solar cell is connected to a circuit by wires leading from the P-layer and the N-layer. When light falls on the surface of the cell, electrons are made to move from one layer to the other. Thus, a current of electricity flows through the circuit.

The first solar cells provided electrical power for space satellites and vehicles. Satellites and space vehicles are still big users of solar cells. Solar cells are now being used to provide electrical power for calculators and similar devices, weather stations in remote areas, oil-drilling platforms, and remote communication relay stations.

The best silicon cells convert only a small portion of the sunlight striking the cells into electricity. The efficiency of solar cells is about 15 percent. This means that 15 percent of the sunlight that strikes the cell is converted into electrical energy. The sunlight that is not converted into electricity either reflects off the surface of the cell or is converted into heat energy.
[am4show have=’p8;p9;p22;p49;p75;p84;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Materials

Silicon solar cell
Two wires with alligator clips on each end of the wires
Earphone or headset for a portable radio
AA-size battery

Download Student Worksheet & Exercises

Procedure

For this experiment you will need a silicon solar cell. Small silicon solar cells are inexpensive and can be purchased at many electronic supply stores.

This experiment should be done on a bright, sunny day.

Examine the metal shaft on the part of the earphone or headset that is inserted into a portable radio. You will notice that just above the tip of the shaft there is a plastic spacer. Clip on one of the wires below this spacer. Then clip on the other wire above this spacer.

To test that the wires are properly connected to the earphone or headset, take the unconnected ends of the two wires and touch them to an AA-size battery. One wire should touch the positive end of the battery, while the other should touch the negative end of the battery. Place the earphone or headset to your ear. If your connections are made correctly, you should hear a crackling sound in the earphone or headset. If you do not hear a crackling sound, check your connections carefully.

Take the earphone or headset, with wires attached, and the solar cell outside into the sunshine. Ask a friend to join you. Your friend can help you hold the solar cell.

Place the earphone or headset to your ear. Ask your friend to hold one of the flat sides of the solar cell facing the sun. The two flat sides of the solar cell are different. In this experiment, you will determine which flat side must face the sun for the cell to generate electricity.

While your friend holds one of the flat sides of the solar cell facing· the sun, you hold one of the alligator clips on the side of the cell facing the sun. At the same time touch the other alligator clip to the opposite side of the cell. As you hold the alligator clips to the cell, avoid blocking the sunlight striking the solar cell.

Ask your friend to turn the solar cell over so that the side that was not facing the sun before now does. Touch a clip to the two sides of the solar cell.

After determining which side of the solar cell needs to face the sun to make a crackling sound in your earphone or headset, ask your friend to hold that side toward the sun. Touch the two alligator clips to each side of the solar cell. Move the alligator clip touching the bottom of the solar cell around the bottom side to keep making the crackling sound in your earphone or headset. Next block the sunlight striking the solar cell.

Observations

Describe the difference between the two sides of the solar cell. Which side must be facing the sun to cause crackling in the earphone or headset when you touch the clips to the solar cell? What happens to the crackling sound when you block the sunlight from striking the solar cell?

Discussion

When you examine your silicon solar cell, you will notice that the two flat sides of the cell are different. One side should have a silvery color, while the other side should appear dark. You should determine in this experiment that one side of the solar cell needs to face the sun for you to hear a strong crackling sound in the earphone or headset. The crackling sound is electricity, generated by the solar cell, passing through the earphone or headset.

Other Things to Try

Repeat this experiment on a cloudy day. Do you still hear a crackling sound in the earphone or headset? If you do hear a crackling sound, is it quieter than on a bright, sunny day?

Is there enough light in a room to cause the solar cell to make electricity? Try it yourself and see.

Exercises

If two electrodes become activated by a current, which way will the ions flow?
1. To the electrode of the same charge
2. To the electrode of the opposite charge
3. None of the above
What type of energy source is the solar panel most closely related to?
1. Biofuel
2. Chemical battery
3. Nuclear reactor
4. Plant energy
The solar cell’s efficiency is not very good. How much of its energy is converted into electricity?
1. 50 %
2. 80%
3. 30%
4. Less than all of these
Name one common use for solar cells:

[/am4show]

Can Water Be Heated With Composting Plant Material?

Friday October 28, 2011

Fossil fuels, which include petroleum, natural gas, and coal, supply nearly 90 percent of the energy needs of the United States and other industrialized nations. Because of their high demand, these nonrenewable energy resources are rapidly being consumed. Coal supplies are expected to last about a thousand years.

We must find other sources of energy to meet the increasing fuel demands of modern society. Important alternate sources of energy include: solar, wind, biomass, hydroelectric, geothermal, nuclear, and tidal energy.

One of the benefits of using alternate sources of energy is that many of them are “clean.” This means that they do not cause pollution. Also, many alternative energy sources are renewable energy sources. They are replaced naturally-such as plant life-or are readily available – such as the sun and wind. In addition, the use of renewable forms of energy will allow us to stretch out our current supply of fossil fuels so they will last longer.

In this chapter you will learn how biomass, or organic matter, can be an important energy source. Plants are the most important biomass energy source. Plant material can be burned directly-as with wood-or it can be converted into a fuel by other means. In the experiments that follow you will explore: how water can be heated by composting grass, how a peanut burns, and how corn syrup can be made into ethyl alcohol.
[am4show have=’p8;p9;p22;p49;p70;p84;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Materials

Freshly cut grass clippings
Cooking thermometer (optional)
Empty two-liter plastic drink bottle
Rake
Water
Styrofoam cup

Procedure

Ask an adult to help you collect freshly cut grass clippings. You will need enough grass clippings to fill about two large grocery bags. Rake the grass clippings into a pile on a shady spot in the yard. In some parts of the country you will only be able to do this in the spring and summer months when grass grows.

Fill a two-liter plastic bottle with cold water. Starting at the top of the pile dig a hole down into the grass clippings just large enough for the plastic bottle. Place the plastic bottle in the hole, and then fill around it with grass clippings. The top of the plastic bottle should stick out of the pile of grass clippings slightly.

Check the water in the bottle after it has been in the pile of grass clipping for at least twenty-four hours. If you have a cooking thermometer, place it in the bottle for thirty seconds and then read the temperature on the thermometer. If you do not have a cooking thermometer, carefully remove the bottle of water from the pile of grass clippings. Feel the sides of the plastic bottle. CAUTION-THE BOTTLE MAY BE VERY WARM, SO AVOID BURNING YOURSELF. Pour some of the water into a Styrofoam cup and look for water vapor rising from the cup. Place the bottle back into the pile of grass clippings and check it again each day for several days.

Observations

After twenty-four hours in the grass clippings, is the water in the plastic bottle warm when you check it? If you check the water with a thermometer, what is the temperature of the water?

When you pour some of the water into a Styrofoam cup, do you see water vapor rising from the cup?

How many days does the water remain warm?

Does the pile of grass clippings become smaller after a few days? What does the pile of grass clippings look like when the water is no longer warm?

Discussion

The water in the plastic bottle should be warm after the bottle has been in the pile of grass clippings for twenty-four hours. The heat that warms the water comes from the pile of grass clippings, which is decomposing or composting.

The decomposition of dead plant and animal material is nature’s way of recycling important chemical substances. Complex chemical substances in dead plant and animal material are broken down into simple chemical substances during the process. These simpler chemical substances then become nutrients for living plants and soil animals.

Heat is given off during the decomposition process. The more material that is decomposing, the more heat is produced. In this experiment, a large amount of heat is given off by the decomposing grass clippings. This is because you started with a large pile of grass clippings, and grass clippings decompose quickly.

A pile of decomposing grass clippings can reach a temperature of over 71°C (160°F). The water in the bottle may absorb enough heat from the decomposing grass to reach a temperature as high as 60°C (140°F) after a day or two. For comparison, most household hot water heaters are set to deliver hot water with a temperature between 54°C (130°F) and 71°C (160°F).

Other Things to Try

How much water can you heat with composting grass clippings? To find out, repeat this experiment with a one-gallon plastic milk jug filled with water. Does the water in the jug become warm?

Repeat this experiment, but remove the bottle of water from the pile of grass clippings after twenty-four hours. Fill a second two-liter plastic bottle with cold water from a sink faucet and place it into the pile of grass clippings. Does the water in this bottle become warm after a couple of hours?

Is there a minimum amount of grass clippings that are needed to make enough heat to heat the water in a two-liter plastic bottle? To find out, surround a two-liter plastic bottle filled with water with just enough grass clippings to cover it. Does the water become warm after twenty-four hours?
[/am4show]

Do Plants Store Energy?

Friday October 28, 2011

A peanut is not a nut, but actually a seed. In addition to containing protein, a peanut is rich in fats and carbohydrates. Fats and carbohydrates are the major sources of energy for plants and animals.

The energy contained in the peanut actually came from the sun. Green plants absorb solar energy and use it in photosynthesis. During photosynthesis, carbon dioxide and water are combined to make glucose. Glucose is a simple sugar that is a type of carbohydrate. Oxygen gas is also made during photosynthesis.

The glucose made during photosynthesis is used by plants to make other important chemical substances needed for living and growing. Some of the chemical substances made from glucose include fats, carbohydrates (such as various sugars, starch, and cellulose), and proteins.

Photosynthesis is the way in which green plants make their food, and ultimately, all the food available on earth. All animals and nongreen plants (such as fungi and bacteria) depend on the stored energy of green plants to live. Photosynthesis is the most important way animals obtain energy from the sun.

Oil squeezed from nuts and seeds is a potential source of fuel. In some parts of the world, oil squeezed from seeds-particularly sunflower seeds-is burned as a motor fuel in some farm equipment. In the United States, some people have modified diesel cars and trucks to run on vegetable oils.

Fuels from vegetable oils are particularly attractive because, unlike fossil fuels, these fuels are renewable. They come from plants that can be grown in a reasonable amount of time.
[am4show have=’p8;p9;p22;p49;p70;p75;p84;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Materials

Shelled peanut
Small pair of pliers
Match or lighter
Sink

Download Student Worksheet & Exercises

Procedure

ASK AN ADULT TO HELP YOU WITH THIS EXPERIMENT. DO NOT DO THIS EXPERIMENT BY YOURSELF. The fuel from the peanut can flare up and burn for a longer time than expected.

Close the drain in the kitchen sink. Fill the sink with water until the bottom of the sink is just covered.

Using a small pair of pliers, hold the peanut over the sink containing water. Ask an adult to hold the flame of a lit match or lighter directly under the peanut. When the peanut starts to burn, the lit match or lighter can be removed.

Allow the peanut to burn for one minute. MAKE SURE AN ADULT REMAINS PRESENT AND MAKE SURE TO HOLD THE PEANUT OVER THE SINK. To extinguish the burning peanut, drop it into the water. After you have extinguished the peanut, allow it to cool and then examine it carefully.

Observations

How long does it take for the peanut to start to burn? Does the peanut burn with a clean flame or a sooty flame? What color is the flame? What color does the peanut turn when it burns? Did the size of the peanut change after it has burned for several minutes?

Discussion

You should find that the peanut ignites and burns after a lit match or lighter is held under it for a few seconds. Although you only let the peanut burn for one minute as a safety measure, the peanut would burn for many minutes.

In this experiment, when the peanut burns, the stored energy in the fats and carbohydrates of the peanut is released as heat and light. When you eat peanuts, the stored energy in the fats and carbohydrates of the peanut is used to fuel your body.

Other Things to Try

Hold one end of a piece of uncooked spaghetti in a pair of pliers. Ask an adult to hold the flame of a lit match or lighter under the other end of the spaghetti. When the spaghetti starts to burn, place it in an aluminum pie pan that is in the sink. Make sure to extinguish the burning spaghetti with water when you are finished with the experiment. How does the burning of the spaghetti compare with the burning of the peanut?

Exercises

What is the process called where plants get food from the sun?
1. Osteoporosis
2. Photosynthesis
3. Chlorophyll
4. Metamorphosis
Where does all life on the planet get its food?
List two ways that we could use the energy in a peanut:

[/am4show]

Classifying Organisms using Little Boxes

Wednesday October 26, 2011

Imagine a little box of spoons. Now, imagine on moving day that that box of spoons is put into a bigger box with all of the silverware. Now, imagine that that box of silverware is placed into an even bigger box with all of the kitchen stuff.

Now, imagine that the box of kitchen stuff is placed in the moving truck with all of the stuff from your house. In the end the within the truck is all of the stuff from your house, within kitchen box are all of the things from the kitchen, and within the spoon box are just the spoons.

In the same way, we will group organisms according to their physical appearance into hierarchical categories.

[am4show have=’p8;p9;p28;p55;’ guest_error=’Guest error message’ user_error=’User error message’ ]

In this unit we’re going to discuss invertebrates by naming what characteristics they have, and placing them in categories accordingly. For example, jellyfish are placed in the Cnidarian category due to their radial symmetry and stinging cells.

Meanwhile Cnidarians are placed in the invertebrate category due to their lack of a backbone. Furthermore, invertebrates are placed in the animal category because they are multicellular, eukaryotic (having cells containing true nuclei), and heterotrophic (required to eat molecules to survive: do not produce their own food).

In this way, we classify animals; we place them in categories according to physical characteristics (modern biology classifies organisms according to DNA similarity) they have (radial symmetry, stinging cells, and lack of backbone, for example).

As you can see, the largest box or category, “animals”, is much larger than the tiny category “jellyfish”. The number of organisms in each category gets progressively fewer as you classify things from animals in general, to jellyfish in particular. The categories follow this structure:

Kingdom: The domain in which living organisms are classified.
Phylum: The subdivision in which all classes below have the same body plan.
Class: Organisms that share one or more attributes.
Order: Containing one or more families.
Family: Organisms descended from the same ancestors sharing relatively similar characteristics.
Genus: Groups of species that are structurally similar or phylogenetically related.
Species: Organisms capable of mating with one another.

An easy way to remember the order of the hierarchy is to think of this mnemonic: Kings Play Cards On Funny Green Stools—each first letter stands for the first letter of a level in the hierarchy (Kingdom, phylum, etc).

For example the classification of the jellyfish the Portuguese Man-O-War (shown):

Kingdom: Animalia (Multicellular, heterotrophic, eukaryotic)
Phylum: Cnidaria (Radial symmetry, stinging cells)
Class: Hydrozoa (very small predatory animals, mostly saltwater, solitary and colonial)
Order: Siphonophora (Colonies of specialized cells which could not survive on their own and resemble one organism)
Family: Physaliidae (Organisms of the genus Physalia)
Genus: Physalia (Colonies of specialized cells which float on the Indian or Pacific Oceans via gas-filled bladders)
Species: P. physalis(Portuguese Man-O-War)

And that’s it! To get a better handle on this (it’s confusing at first!), here’s a simple activity you can do that’s fun and easy. Here’s what you need:

Card stock
Printer
Ziploc bags

Here’s what you do:

Print out the Challenge: Classifying Invertebrates file. You’ll want to print several copies the cards on card stock. You should have enough so that each team (or each student) gets a complete set of cards. They can be stored in zipper-type bags for future use.
Work in teams to correctly classify the invertebrates. You can compare your answers to the key shown below.
For more of a challenge, time yourselves to see which team (or student) can complete the classification fastest. One player shuffles the cards and places them in a pile, then serves at the times for the other team.
When you’re ready for answers, print out the Answer Key.

[/am4show]

Nuclear Reactions & Radioactive Decay

Monday October 24, 2011

If you think about it, the nucleus of an atom (proton and neutron) really have no reason to stick together. The neutron doesn’t have a charge, and the proton has a positive charge. And most nuclei have more than one proton, and positive-positive charges repel (think of trying to force two North sides of a magnet together). So what keeps the core together?

The strong force. Well, actually the residual strong force. This force is the glue that sticks the nucleus of an atom together, and is one of the strongest force we’ve found (on its own scale). This force binds the protons and neutrons together and is carried by tiny particles called pions. When you split apart these bonds, the energy has to go somewhere… which is why fission is such a powerful process (more on that later).

The fundamental strong force holds the quarks together inside the proton and neutron. Itty bitty particles called gluons hold the quarks together so the atom doesn’t fly apart. This force is extremely strong – much stronger than the electromagnetic force. This force is also known as the color force (there is not any color involved – that is just the way it was named.)

The electromagnetic force keeps the electrons from flying away from the nucleus. When a plus (the nucleus) and minus (the electron) charge get close together, tiny particles called photons pull the two together.

What is Radiation?

Radiation is energy or parts of atoms that are given off. We measure radiation with a geiger counter, which has a tube of gas inside that every time it gets hit by radiation, it gives off a little electrical charge.

[am4show have=’p8;p9;p17;p44;’ guest_error=’Guest error message’ user_error=’User error message’ ] In the 20th century, scientists figured out that the core of an atom can break apart or join together with others. If you split an atom (called fission), you get smaller parts and a whole lot of energy. When this happens in nature, it’s called radioactivity. Unstable atoms spontaneously break apart and release particles and energy.

Here’s a cool video that shows the fission chain reaction (you can do this also if you have a box, at least 25 mouse traps and 25-50 ping pong balls with adult help):

Fusion is taking place inside the sun. The sun is not on fire, like a campfire or stove. So where does it get its energy from? The fusion process smacks particles together, which results in a big release of energy. The core of the sun is about one million degrees Celsius, which the surface temperature is a mere 15,000 degrees Celsius. The fusion process in the sun takes two naked protons (also known as a hydrogen nuclei) and smacks them together in a special sequence that results in the formation of helium. This complicated reaction is called the proton-proton chain, and occurs in all stars burning hydrogen in their core.

Radioactivity can be dangerous, but it isn’t always dangerous. For example, your household smoke alarm emits alpha particles (the main detector uses alpha decay), brick and mortar building emit beta particles, and gamma particles come directly from the sun. In fact, people themselves emit beta particle radiation! When an atom of radioactive material decays, there are three types of radiation that it may emit: alpha, beta, and gamma. Generally speaking, most radioactive materials emit two, or all three types of radiation.

Alpha particles were named long before we ever knew what they were. An alpha particle are two protons and two neutrons stuck together (also known as helium nuclei). Beta particles are either electrons or positrons. Gamma particles, also called gamma rays, are actually electromagnetic radiation (photons) of very, very high frequency and energy – high enough to damage living tissue. Fortunately, gamma ray bursts are rare and usually not pointed in our direction.

Alpha particles are relatively slow and heavy. They have a low penetrating power, so you can stop them with just a sheet of paper. Alpha particles can not penetrate your skin. Due to the low penetrating power of Alpha particles, they are generally not a cause for concern, unless you ingest some material that emits Alpha radiation. For the most part, materials that emit Alpha particles, also emit some Beta or Gamma radiation.

Beta particles are fast and light. Beta particles have a medium penetrating power, but they are stopped by a thin sheet of aluminum (such as aluminum foil) or plastic. Beta particles can penetrate deeply into your skin.

Gamma rays have a high penetrating power. It takes a thick sheet of metal such as lead, or concrete to reduce them significantly. If you want to stop all gamma rays dead in their tracks, you’d need a sheet of lead 27 light-years thick. (Yikes!) Gamma rays penetrate your skin, and continue going right through your body.

The really unusual aspect of radiation is that the emission levels stays constant, no matter how hot or cold you make the material, or if you shove it into the deep vacuum of space or increase the pressure to bursting, the rate of natural radioactive decay from radioactive materials will always remain the same. This is why materials of this type are used in Atomic Clocks.

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Why do birds migrate?

Monday October 24, 2011

Imagine leaving your home every year and traveling hundreds of miles to a completely different place, only to return home later in the year. As amazing as this sounds, this is exactly what many species of birds do in a process called migration.

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So why do birds migrate? The two main reasons are for food and breeding (reproduction.) Imagine a bird that lives in the Arctic. During the cold winter, the birds simply leave and fly to warmer locations. When summer returns, they return as well. Back in the Arctic, they are the first animals there to look for new food sources, giving them a huge advantage. What’s more, since there aren’t that many animals that can survive the winter, the birds face fewer predators. They can lay their eggs with less risk of them being eaten.

The most common kind of migration involves a bird flying from the North to the South in the winter, this is not the only type of migration. Some birds migrate horizontally, meaning they go from one coast to the other, where they find pleasant climates. Others migrate down mountains in the winter, since it’s colder the higher up a mountain you go. Some birds that don’t fly migrate on foot or by swimming.

Migrating birds do get some help. They use wind currents to help them fly faster while using less energy. Some large birds get lifted up by hot air rising. Birds also have extra fat reserves which provide them with energy, and often will stop for a few days to “re-fuel” (although some do fly non-stop). With this help, birds can migrate remarkable distances. The Arctic tern is the record holder, with an incredible 20,000 km journey from the North to the South Pole!

One of the most amazing things about bird migration is that no one ever teaches the bird how or where to migrate. Instead, birds rely on the location of the sun and stars, knowing which direction is North, and sounds and smells, like the smell of the ocean or the waves crashing against the shore, to complete their incredible journey.

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Cartesian Diver

Sunday October 23, 2011

Rene Descartes (1596-1650) was a French scientist and mathematician who used this same experiment show people about buoyancy. By squeezing the bottle, the test tube (diver) sinks and when released, the test tube surfaces. You can add hooks, rocks, and more to your set up to make this into a buoyancy game!
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The test tube sinks because the when you squeeze the bottle, you increase the pressure of the water and this forces water up into the test tube, which then compresses the air inside the tube. When this happens, it adds enough mass to cause it to sink. Releasing the squeeze on the bottle means that you decrease the pressure and the water is forced back out of the tube.

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Can a Fuel be Made From Plant Material?

Sunday October 23, 2011

Yeast is a simple living organism that can break down sugars into ethyl alcohol (ethanol) and carbon dioxide. The process by which yeast breaks down sugars into ethyl alcohol and carbon dioxide is called fermentation.

The tiny gas bubbles rising in the liquid mixture in the bottle are carbon dioxide gas bubbles that are made during the fermentation. The balloon on the bottle expands and becomes inflated because it traps the carbon dioxide gas being produced.

The ethyl alcohol that is made during fermentation stays in the liquid mixture. When fermentation is finished, the liquid mixture usually contains about 13 percent ethyl alcohol. The rest of the liquid is mostly water.

The ethyl alcohol can be concentrated by a process called distillation. During distillation, the liquid fermentation mixture is heated to change the ethyl alcohol and some of the water into a vapor. The vapor is then cooled to change it back into a liquid. This distilled liquid contains 95 percent ethyl alcohol and 5 percent water. The remaining water can be removed by special distillation methods to give pure ethyl alcohol.

In some areas of the United States, ethyl alcohol is blended with gasoline to make a motor fuel known as gasohol. About 8 percent of the gasoline sold in the United States is gasohol.

Gasohol burns more cleanly than pure gasoline. This results in fewer pollutants being released into the air. The use of gasohol as a motor fuel is particularly important in cities that have a lot of smog.

Corn syrup is a mixture of simple and complex sugars and water. It is made by breaking down the starch in corn into sugars. The process is called digestion. In this experiment you changed the sugars in corn syrup using yeast. Much of the ethyl alcohol used to prepare gasohol is made by fermenting corn and corn sugar.

Over one billion gallons of ethyl alcohol are made each year by fermentation of sugars from grains such as corn. Ethyl alcohol is a renewable energy source when it is made by fermenting grains such as corn. This is because the grains, such as corn, are easily grown.

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Materials

One package of yeast
Balloon
Water
Measuring spoons
Corn syrup
Measuring cup
Empty, two-liter plastic drink bottle
Funnel (optional)
Sink or bucket

Procedure

Remove the paper label from around an empty, two-liter, plastic drink bottle. Add two cups of water and one package of yeast to the bottle. Swirl the bottle to mix the water and yeast.

Next, add one-quarter cup of corn syrup to the bottle. You may want to use a small funnel to help you add the corn syrup to the bottle. Swirl the bottle to mix the contents.

Place a deflated balloon over the neck of the bottle. Make sure the balloon fits securely over the neck. Place the bottle in a sink or bucket. Check the bottle and balloon after two hours, and then again after four hours. Finally, check the bottle and balloon after twenty-four hours.

When you have finished with the experiment, pour the contents of the bottle down the sink. Then rinse the bottle and sink with water.

Observations

What color is the yeast mixture? Does the balloon start to inflate after an hour or two? Can you see gas bubbles rising to the surface of the yeast mixture? Does the balloon grow larger with time?

Discussion

You should find that soon after you mix together the yeast, water, and corn syrup, changes start to take place in the bottle. You should notice that a foam forms on top of the liquid mixture. You should also see tiny gas bubbles rising to the surface of the liquid. Also, you should notice that the balloon begins to inflate and become large.

Other Things to Try

Repeat this experiment using one tablespoon of table sugar instead of corn syrup. You should find that yeast can also ferment table sugar into ethyl alcohol and carbon dioxide. Table sugar is made from sugar cane and sugar beets. Since sugar cane and sugar beets are renewable plants, ethyl alcohol made from fermenting sugar from these plant products is another renewable energy source.

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What are Aurorae?

Saturday October 22, 2011

Aurora, or ‘northern lights’, is the natural light display in the sky in northern regions like Canada, Alaska, and northern Eurpoean countries that have had people puzzled for centuries as to what exactly they were, and how the light displays were made. Here’s a rare view of the aurorae taken from the International Space Station:

Auroras (or aurorae) happen about 50 miles up, when solar wind hits particles in the Earth’s atmosphere. When charged particles from the solar wind hit the Earth’s magnetosphere (a magnetic field that extends far beyond the Earth’s surface and protects us from solar wind), they are funneled by the Earth’s magnetic field. When these highly charged particles from the sun hit a molecule in our atmosphere, they give off a photon. The green and brownish-red colors come from oxygen and the blue and red are from nitrogen.

In northern latitudes, the aurora borealis was named after the Roman goddess of dawn (Aurora) and the Greek name for the north wind (Boreas). In the south, the aurora australis (or the southern lights) appear anytime the northern lights are visible. This effect is also seen on other planets like Jupiter and Saturn.

Shopping List for Unit 18

Friday October 21, 2011

How many of these items do you already have? We’ve tried to keep it simple for you by making the majority of the items things most people have within reach (both physically and budget-wise).

Here’s how to use this shopping list: First, look over the list and circle the items you already have on hand. Browse the experiments and note which ones use the materials you already have. Those are the experiments you can start with. After working through the experiments, your child might want to expand and do more activities. Make a note of the materials and put them on your next shopping trip OR order them online using the links provided below.

We’ve tried to keep it simple for you by making the majority of the items things most people have within reach (both physically and budget-wise). Are you ready?

Shopping List for Unit 18: Click here for Shopping List for Unit 18.

Material List:

Chicken egg
Vinegar
Glass
Roasted chicken
Variety of bird feathers (collected from nature)
Dead insects of your choice
Birdseed
Poster board in a variety of colors
Water bottle
2 flexible straws
Fifteen clean and empty 2-liter soda bottles with caps (check your local recycling center)
One small plastic lid that fits inside the soda bottle (like from a yogurt or butter tub)
Aluminum foil (12” piece)
Plastic vial (like an M&M container or a film canister)
1 yard (or meter) of cotton twine or rolled up paper towel
Brown paper grocery bag
Newspaper
fast-growing plant seeds (radish, grass, turnips, Chinese cabbage, moss, etc.)
Flexible or clip-on style lamp with fluorescent bulb
Soil, twigs, leaves, and organic plant material
Live predators (praying mantis or spiders or carnivorous plants)
Live red worms (about 20)
Small piece of fruit
White and black spray paint
20 feet of rope
Graph paper (optional)
Non-flexible straw
Salt
Glass
Distilled water or filtered water
Permanent marker
Clay (about the size of a marble)
Paint can (we’ll use the lid for the secchi disk and the pail for the waterscope) OR plastic gallon-size jug
Large rubber band
Plastic film (like saran wrap)
Lizard in a terrarium (borrow one?)
Video camera
Male betta fish
Fish bowl
Mirror for fish bowl

Tools:

scissors
razor with adult help
hot glue gun
masking tape

Optional Dissection Materials:

Simple dissection tools (forceps, tweezers, scissors, scalpel, T-pins, mounting board, clear plastic ruler)
Starfish specimen
Earthworm specimen
Clam or oyster specimen
Owl Pellet

Water Cycle Column: Is Rain Pure?

Friday October 21, 2011

When birds and animals drink from lakes, rivers, and ponds, how pure it is? Are they really getting the water they need, or are they getting something else with the water?

This is a great experiment to see how water moves through natural systems. We’ll explore how water and the atmosphere are both polluted and purified, and we’ll investigate how plants and soil help with both of these. We’ll be taking advantage of capillary action by using a wick to move the water from the lower aquarium chamber into the upper soil chamber, where it will both evaporate and transpire (evaporate from the leaves of plants) and rise until it hits a cold front and condenses into rain, which falls into your collection bucket for further analysis.

Sound complicated? It really isn’t, and the best part is that it not only uses parts from your recycling bin but also takes ten minutes to make.

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Here’s what you need:

three 2-liter soda bottles, empty and clean
razor with adult help
scissors
tape
ruler
60 cm heavy cotton string
soil
water
ice
plants
drill and drill bits
fast-growing plant seeds (radish, grass, turnips, Chinese cabbage, moss, etc.)

Here’s what you do:

Download Student Worksheet & Exercises

Make sure your wicks are thoroughly soaked before adding the soil and plants! You can either add ice cubes to the top chamber or fill it carefully with water and freeze the whole thing solid. If you’re growing plants from seeds, leave the top chamber off until they have sprouted.

You can add a strip of pH paper both inside and outside your soil chamber to test the difference in pH as you introduce different conditions. You can check out the Chemical Matrix Experiment and the Acid-Base Experiment also!) What happens if you light a match, blow it out, and then drop it in the soil chamber? (Hint – you’ve just made acid rain!)

Do you think salt travels with the water? What if you add salt to the aquarium chamber? Will it rain salty water? You can place a bit of moss in the collection bucket to indicate how pure the water is (don’t drink it – that’s never a good idea).

Exercises

Do you think salt travels with the water?
What if you add salt to the aquarium chamber? Will it rain salty water?
What happens if you light a match, blow it out, and then drop it in the soil chamber? (Hint – you’ve just made acid rain!)

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Terraqua Column

Friday October 21, 2011

How does salt affect plant growth, like when we use salt to de-ice snowy winter roads? How does adding fertilizer to the soil help or hurt the plants? What type of soil best purifies the water? All these questions and more can be answered by building a terrarium-aquarium system to discover how these systems are connected together.

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Here’s what you need:

two 2-liter soda bottles, empty and clean
two bottle caps
scissors and razor with adult help
tape
water, soil, and plants

Here’s what you do:

Download Student Worksheet & Exercises

Water drips off the roof of your house, down your driveway, over your toothbrush and down the sink, through farm fields, and into rivers, lakes and oceans. While traveling, this water picks up litter, nutrients, salts, oil, and also gets purified by running through soil. All of this has an affect on fish and animals that live in the oceans. The question is, how does it affect the marine ecosystem? That’s what this experiment will help you discover.

Land and aquatic plants are excellent indicators of changes in your terraqua system. By using fast-germinating plats, you’ll see the changes in a relatively short about of time. You can also try grass seeds (lawn mixes are good, too), as well as radishes and beans. Pick seeds that have a life cycle of less than 45 days.

How to Care for your TAC (Terra-Aqua Column) EcoSystem:

Keep the TAC out of direct sunlight.
Keep your cotton ball very wet using only distilled water. Your plants and triops are very sensitive to the kind of water you use.
Feed your triops once they hatch (see below for instructions)
Keep an eye on plant and algae growth (see below for tips)

About the plants and animals in your TAC:

Carnivorous plans are easy to grow in your TAC, as they prefer warm, boggy conditions, so here are a few tips: keep the TAC out of direct sunlight but in a well-lit room. Water should condense on the sides of the column, but if lots of black algae start growing on the soil and leaves, poke more air holes! Water your soil with distilled water, or you will burn the roots of your carnivorous plants. Trim your plants if they crowd your TAC.
If you run out of fruit flies, place a few slices of banana or melon in an aluminum cup or milk jig lid at the bottom of a soda bottle (which has the top half cut off). Invert the top half and place it upside down into the bottom part so it looks like a funnel and seal with tape so the flies can’t escape. Make a hole in the cap small enough so only one fly can get through. The speed of a fruit fly’s life cycle (10-14 days) depends on the temperature range (75-80 degrees). Transfer the flies to your TAC. If you have too many fruit flies, discard the fruit by putting it outside (away from your trash cans) or flush it down the toilet.
You can’t feed a praying mantis too much, and they must have water at all times. You can place 2-3 baby mantises in a TAC at one time with the fruit flies breeding below. When a mantis molts, it can get eaten by live crickets, so don’t feed if you see it begin to molt. When you see wings develop, they are done fully mature. Adult mantises will need crickets, houseflies, and roaches in addition to fruit flies.
Baby triops will hatch in your TAC aquarium. The first day they do not need food. Crush a green and brown pellet and mix together. Feed your triop half of this mixture on the 2^nd and the other half on the 4^th day (no food on day 3). After a week, feed one pellet per day, alternating between green and brown pellets. You can also feed them shredded carrot or brine shrimp to grow them larger. If you need to add water (or if the water is too muddy), you can replace half the water with fresh, room temperature distilled water. You can add glowing beads when your triop is 5 days old so you can see them swimming at night (poke these through the access hole).

Exercises

What three things do plants need to survive?
What two things do animals need to survive?
Does salt affect plants? How?

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Finding the Secchi Depth

Friday October 21, 2011

Secchi Disc — Image courtesy of KIS 2020 Challenge: Chao Phraya River.

Often marine scientists as well as fisherman want to test the murkiness (or turbidity) of the water. How can you do this quickly and accurately? Well, first you’ll need a Secchi Disk. With the cheap, easy-to-make Secchi Disk you can test water quality like a pro!

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The Secchi disk was invented in 1865 by Pietro Angelo Secchi, and it’s basically a circular disk hung from a rope and lowered slowly in the water until you can’t see the pattern on the disk anymore. Scientists call this depth the Secchi depth and is related to water transparency.

As you probably figured out, Secchi disk readings are not an exact measure of transparency, because it depends not only on a person’s eyesight but also the brightness of the day. But for most folks, the measurement is quick, inexpensive and relatively accurate for their needs.

The results are best when the disk is used between 10:00 am and 2:00 pm on the shady side of the boat or dock and the reading should be done by the same person. Both Minnesota and Indiana field scientists use this technique when assessing the quality of water in their lakes.

Here’s what you’ll need:

A white plastic disk with an 8 inch diameter. A paint or bucket lid works well.
A permanent marker.
A broom handle (unless you’re measuring very clear water, and in that case use string).
Graph paper.

Here’s what you do:

Divide the disk into four sections with the permanent marker. Color in two of the sections (such that if moving clockwise the sections alternate between being filled in and not filled in).
Attach the lid to the broom handle or string (if using the string, attach a weight to the other side of the lid).
Lower the disk into the water until you can’t distinguish between the dark and light sections. Mark that depth.
Pull the disk up and measure the first depth. Note that on the paper.
Lower the disk past the first mark and then pull it up until you can just make out the difference between the dark and light sections of the disk.
Pull the disk up, measure the second distance, and note it.
The average between the two depths is the Secchi depth.

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Homemade Hydrometer

Friday October 21, 2011

With a name like hydrometer you might pause and say: “…a what?” You might have even gone a step further and added “why do I want one of those?” Simply put, hydrometers test the density of liquids. Specifically, they compare the density of liquids to the density of water (a comparison called the specific gravity of a substance). A substance’s specific gravity is extremely useful. We use it to tell how creamy milk is, how much alcohol is in spirits, how salty the ocean is, and much more! In the following experiments we’ll test the salinity of several solutions.

(Note: This is different from a hygrometer, which measures the humidity of the air!)

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Here’s what you need:

Drinking straw
Modeling clay
A drinking glass
Salt
Distilled water (or as filtered as you have on hand)
Permanent marker
Graph paper (optional)

Download Student Worksheet & Exercises

Here’s what you do:

Plug one end of the straw with a small marble-size ball of clay. This is your hydrometer.
Fill your glass with water (find a glass that holds about 2 to 2.5 cups of water).
Place the hydrometer in the glass. Add or remove clay until the straw floats midway up your glass. Mark that level “0” with the permanent marker (because there is no salt).
Remove the hydrometer.
Add 1 teaspoon of salt to the water.
Place the hydrometer in the glass. Mark the new level and label it “10” for 10 ppt (parts per thousand).
Add another teaspoon of salt to the solution.
Repeat step 6 (except this time mark the level “20” for 20ppt).
Repeat until you have marks up to 50 (or higher!).
Have a partner prepare unknown solutions of salt and water. Test them with the hydrometer. Graph your findings. Extra credit: try solutions at different temperatures!

How does it work?! The hydrometer works via the Archimedes Principle which states that an object will be buoyed up by the force equal to the weight of the fluid displaced. Thus, the more dense the fluid, the more force it exerts on objects floating in it. This is why the hydrometer moves higher as more salt is added. Cool, huh?

Troubleshooting: Is your hydrometer not working correctly? First, check the plug. If the plug is letting water the hydrometer may be getting heavier as you add salt—the opposite result you expect!

Exercises

What do hydrometers test?
What is specific gravity?
What is the Archimedes Principle?
Would a boat float better in water or honey? Why?

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Consuming Oxygen

Tuesday October 18, 2011

This experiment not only explains how your body uses oxygen, but it is also an experiment in air pressure circles – bonus! You will be putting a dime in a tart pan that has a bit of water in it. Then you will put a lit candle next to the dime and put a glass over the candle with the glass’s edge on the dime. Once all of the air inside the glass is used up by the candle, the dime will be easy to pick up without even getting your fingers wet! Ready to give it a try?

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Here’s what you need

- 1 aluminum tart pan
- 1 votive candle
- 1 box of matches
- 1 clear drinking glass, 12 or 16 oz.
- 1 dime
- water
- 1 pair of goggles
- Adult supervision!

Download Student Worksheet & Exercises

Here’s what you do

Pour about ¼ inch of water in the pan and place the dime right in the middle.
Position the candle next to the dime and ask an adult to light it for you
Put the drinking glass over the candle with its edge resting on the dime. Watch closely to observe what happens.
Once the water is inside the glass, you can carefully remove the dime from under its edge. If done properly, the water will stay in the glass.

What’s going on?

When you put the glass over the candle, you created a closed system. The candle only had the gas trapped inside the air beneath the glass to burn. As the candle burned, the gases in the glass burned as well. They were transformed from a state of gas to a very compact solid state that stuck to the wick of the candle (this is why the wick gets black when a candle burns).

An important thing to note is that as the air was removed, the pressure inside the glass was reduces. Lower air pressure inside your closed system created an imbalance with the regular air pressure on the outside of the glass. Since there was more pressure on the outside, the water was pushed inside the glass. The dime helped to make a gateway for the water to be more easily pushed into the glass.

This lab serves to illustrate that oxygen is consumable. It’s the same thing that happens inside your body, but at a much slower rate that what you witnessed with the candle. Your lungs contain about 1,490 miles (2,400 km) of air passages to help absorb oxygen. If they could be spread out flat, an average set of lungs have a surface area of approximately 650 square feet. The sheer size of this system gives you the chance to absorb all the oxygen that your body needs.

Exercises

What do we mean when we say that oxygen is consumable?
What is the difference between an open and a closed system?
Where is the higher pressure in this experiment?
Why does water rise inside the glass?

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Make an Insect Aspirator

Monday October 17, 2011

Some insects are just too small! Even if we try to carefully pick them up with forceps, they either escape or are crushed. What to do?

Answer: Make an insect aspirator! An insect aspirator is a simple tool scientists use to collect bugs and insects that are too small to be picked up manually. Basically it’s a mini bug vacuum!

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Download Student Worksheet & Exercises

Here’s what we’ll need:

A small vial or test tube with a (snug fitting) two-holed rubber stopper.
Two short pieces of stiff plastic tubing. We’ll call them tube A and tube B.
Fine wire mesh (very small holes because this is what will stop the bugs from going into your mouth!)
A cotton ball.
One to two feet of flexible rubber tubing.
Duct tape or a rubber band.

Here’s how we make it:

Insert the tube A and Tube B into the stopper such that the stopper is in the middle of both pieces.
Bend both A and B plastic tubing 90 degrees away from each other. Their ends should be pointing away from each other.
Cut a square of mesh large enough to the end of the plastic tubing. Tape (or rubber-band) the mesh over bottom of tube A only. Remember, if you cover both of the tubes the bugs won’t be able to enter the aspirator.
Insert a small amount of cotton ball into the other side of tube A (not enough to block airflow, just enough to help filter the dust and particles entering the vial.
Cut another piece of mesh and cover the other end of Tube A. Secure that mesh with another piece of tape/rubber band.
Fit the rubber tubing over the top of tube B (the bent side).
Fit the stopper into the vial/test tube.

How it works: To use the aspirator, hold the end of the rubber tubing near the insects you want to collect, and suck through the top of tube A. The vacuum you create sucks the insects into the vial/test tub (make sure they can fit in the tube!).

Troubleshooting: The bugs aren’t being pulled into the vial! In that case the suction may not be strong enough. Remove the cotton ball and try again. If it still is not working check to make sure the aspirator is air-tight (is the stopper fitting snuggly into the vial? Are there cracks/holes around or in the plastic tubes?).

TIP: I kept eating bugs! Make sure your wire mesh is very fine (the holes are smaller than the bugs you’re trying to collect). Otherwise you may be ordering a lunch you don’t want!

Exercises

Why don’t we use a large vacuum to suck up the bugs?
Why do we need a small mesh covering on the end of the straw that we suck on?
Why do we need to be careful about catching ants?
What insects did you catch that you rarely see?
What familiar insects did you catch? (answers may vary).

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Berlese funnel

Monday October 17, 2011

Unsurprisingly, often the most interesting critters found in soil are the hardest to find! They’re small, fast, and used to avoiding things that search for them. So, how do we find and study these tiny insects? With a Berlese Funnel (Also called the Tullgren funnel)!

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The funnel separates the insects from the soil with heat. A light bulb heats the soil at one end of a funnel and causes the insects to migrate, through mesh, to a preservative liquid at the other end of the funnel. Originally Antonio Berlese used a hot water bottle to provide the heat. Later, Albert Tullgren modified the funnel to work with a light bulb. Thus, we now call it the Berlese Funnel, the Tullgren Funnel, or the Berlese-Tullgren Funnel.

Download Student Worksheet & Exercises

An ultraviolet lamp used to attract night flying insects. The simplest set up is to hang a white sheet on a line and hang a portable black light on one side of the sheet. Insects will land on the sheet and can be tallied, identified or collected.

To make a larger, more permanent model, here’s what you need:

1 gallon tractor funnel.
Clothespins.
A light fixture that fits on top of the funnel and has a reflective interior.
A bucket that has a smaller diameter than the top of the funnel. The funnel needs to be suspended from the bucket so the insects can fall into the jar.
A clean jam-jar.
Rubbing alcohol.
¼ inch wire mesh.
Light bulb. The wattage has to be high enough to heat the soil, but not so high that it will light the funnel on fire. Best to do it by trial and error with lots of supervision.
Soil. The best will be from a compost pile.

Here’s how you make the funnel:

Cut a large hole in the side of the bucket. This will allow you to retrieve the jar without disassembling the apparatus. Naturally, the hole should be larger than the jar.
Fit the wire mesh so that it covers the bottom third of the funnel.
Fit the funnel on top of the bucket.
Fit the light fixture (with the light bulb in it) on top of the funnel with the clothespin.
Place the jar underneath the funnel (with or without the rubbing alcohol depending on if you want the specimens dead or alive).

How to use the funnel: Simply turn on the light and wait. Check the vial every fifteen minutes or so for an hour. After you have finished remember to turn off the light! Also, remember that some of the specimens may be very small and best observed under a microscope. For the best results do it in the morning or on a cold day.

How the funnel works: Figure 1 shows the funnel in action. The light (G) creates heat. The insects in the soil don’t like heat, so they move from the soil (D) through the funnel (C) into the jar (B). The jar is filled with rubbing alcohol (A) preserves the specimens. The wire (not shown in the figure) keeps most of the soil from falling into the jar.

Troubleshooting: What if there still aren’t any bugs after an hour? If this happens, don’t panic. Ask yourself these questions:

Is the light strong enough? If the light is not strong enough (i.e. generating enough heat), then the soil will not get hot enough to push the insects into the jar. The funnel works by creating a gradient of heat which the bugs move down into the jar. If the light isn’t creating that gradient, no critters will feel like moving.
Is it hot today? If the sun is out and making everything hot, then the light will not make enough of a difference in heat—there will not be a heat gradient to move down. If so, don’t worry; just try again the next morning.
Is there a problem with the funnel? Is the nozzle of the funnel too far from the mouth of the jar? Make sure that the specimens are falling into the jar and not around it. Is the mesh wire too fine? You want mesh that will keep most of the soil in the funnel, but not so fine that it will stop the bugs from getting through.
Lastly, are there any bugs in the soil? Not just any dirt will do for this project. You need soil rich with life! The best place to find this type of soil is near/in a compost pile (after it has become soil).

Exercises

Why are some insects difficult to find in soil?
Why does the Berlese Funnel work to find insects?
What if the insects do not respond to the heat lamp in your experiment?
What types of insects were you able to find using the Funnel?

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Make a Waterscope

Monday October 17, 2011

As you walk around your neighborhood, you probably see many other people, as well as some birds flying around, maybe some fish swimming down a local stream, and perhaps even a lizard darting behind a bush or a frog sitting contently on top of a pond. Most likely, you know that all of these living things are animals, but they are even more closely related than that.

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Tide pools are best observed undisturbed. But, they’re too shallow to snorkel… So how to can we explore them without removing their inhabitants? With an Aquascope! Aquascopes are very cheap and easy to make. With only a coffee can, some plastic food rap, and a couple of other items you can make a window into the world of tide-pools! In principle, aquascopes allow us to take a glass-bottom-boat tour of the rich ecosystems of tide pools. The plastic acts as the glass, while the coffee can allows us to break the distorting surface of the water.

Here’s a video to get you started:

Download Student Worksheet & Exercises

Here’s what you need:

milk or juice jug
plastic wrap
scissors
rubber band

Here’s the steps to make the waterscope:

Clean out your jug first. Then cut the bottom and top off without cutting off the handle.
Cover the opening at the bottom with your plastic wrap, securing it in place with the rubber band. Use tape if you need extra support to hold the plastic wrap in place. The window needs to be water-tight.
Place the waterscope in the water, bottom-side down. You’ll be able to see all kinds of interesting creatures through your scope!
Try to keep your scope still so the animals won’t be afraid to come close to you so you can have a good peek at their world. The aquascope works the same way snorkel goggles work—except you don’t have to get wet!

Why this works: You can’t see clearly underwater with just your eyes for a couple of reasons. One is the thickness of the lens on your eye, but the main one is the index of refraction of water is different than that of air. Light rays bend when they travel from one medium to another of different density (refer to the Disappearing Beaker experiment for more on this topic). The amount that the light bends depends on refractive index of each substance along with the shape. The eye focuses images on the retina, and our eyes are built for viewing in air. Water has approximately the same refractive index as the cornea which effectively eliminating the cornea’s focusing properties. This is why you see a blurred image underwater. The eyes are focusing the image them far behind the retina instead of on the retina. The waterscope puts a layer of air between your eyes and the water (the same way goggles do) so you can view underwater without blurred vision.

Troubleshooting: The key to the aquascope is the taught plastic wrap. If it’s loose, or if there are holes, it won’t work as well. Make sure that the plastic wrap is securely fastened to the can, and is stretched tight. If you find your waterscope leaks, use a stronger rubber band to secure your plastic wrap in place. You can alternatively use strong waterproof tape or hot glue to secure it in place, but use the rubber band first so you can stretch the film tightly over the open end.

Exercises

What is the term for light rays bending?
Why is underwater vision blurred?
How can we focus vision underwater?

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How Lungs Work

Sunday October 16, 2011

Take a deep breath in, and slowly let it out. As you do, think about the breaths you take without thinking about it. The truth is, you probably only think about breathing when you are coughing and having a hard time breathing. Even though breathing is not something we think about regularly, it is absolutely required for the survival of the cells in your body. As you breathe, oxygen flows into the body and carbon dioxide flows out. This very important exchange of gases is the main function of your body’s respiratory system.

Sometimes, people will say “breathing” and “respiration” as though they were the same thing, but they are actually very different. Breathing is the process where air enters the body, goes into the lungs, and exchanges its oxygen for carbon dioxide. This is part of respiration, and is known as external respiration, but it only half of full respiration. Respiration also includes internal respiration, where the blood, full of oxygen, goes to the parts of the body that need it. This process can be learned about in a discussion of the circulatory system, another body system.

Measuring the Heart’s Health

Sunday October 16, 2011

The heart is the most important organ in the cardiovascular system. You may heard your heart beat when you were at the doctor’s office, but you may never have thought about what the heart was actually made of. The heart is made of four sections, or chambers. The two chambers at the top of the heart are called the left atrium and right atrium. The two chambers at the bottom of the heart are called the left ventricle and right ventricle.

The job of the atria (that’s the plural of atrium) is to get blood from the other parts of the body. The job of the ventricles is to pump the blood from the heart to other parts of the body. We’ll worry about exactly where the atria are getting the blood from and where the ventricles are sending it to a little later. For now, just make sure you understand that atria get blood in and ventricles pump blood out.

Along with the heart, another important part of the cardiovascular system are blood vessels. There are three main types of blood vessels; arteries, veins, and capillaries. Arteries are blood vessels that carry blood away from the heart. Arteries have thick walls. They need these thick walls because there is a lot of pressure on the blood in arteries. Every time the heart contracts, it creates a force on the walls of the arteries. This force creates pressure. You’ve probably heard of blood pressure, and had your blood pressure taken during a check-up.

Blood pressure is a measure of the pressure on the walls of the arteries caused by your beating heart.
The next types of blood vessels are veins. In many ways, veins are the opposite of arteries. While arteries move blood away from the heart, veins bring blood back to the heart. While arteries have thick walls to handle blood under high pressure, the walls of veins are much thinner, because the blood they carry is under a much smaller amount of pressure. Veins contain valves, which stop the blood they are carrying from moving backwards.

The last types of blood vessels are capillaries. Capillaries connect veins and arteries, and they are tiny. Their walls are only one cell thick, and they are so narrow, blood cells have to go through them single file. In spite of their small size, however, capillaries are the place where one of the most important things in our body happens. Networks of capillaries, called capillary beds, are the places where blood gives off oxygen to the parts of the body, and collects waste products like carbon dioxide. One of the major purposes of the cardiovascular system, oxygen transfer, is happening in these tiny vessels. The more active an organ is, the more capillaries it will need to get oxygen and other nutrients from the blood.

Predator-Prey: Who Eats Whom?

Sunday October 16, 2011

The way animals and plants behave is so complicated because it not only depends on climate, water availability, competition for resources, nutrients available, and disease presence but also having the patience and ability to study them close-up.

We’re going to build an eco-system where you’ll farm prey stock for the predators so you’ll be able to view their behavior. You’ll also get a chance to watch both of them feed, hatch, molt, and more! You’ll observe closely the two different organisms and learn all about the way they live, eat, and are eaten.

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This experiment comes in two parts. The materials you need for both parts are:

four 2-liter soda bottles, empty and clean
2 bottle caps
one plastic lid that fits inside the soda bottle
small piece of fruit to feed fruit flies
aluminum foil
plastic container with a snap-lid (like an M&M container or film can)
scissors and razor with adult help
tape
ruler
predators: spiders OR praying mantis OR carnivorous plants (if you’re using carnivorous plants, make sure you do this Carnivorous Greenhouse experiment first so you know how to grow them successfully)
soil, twigs, small plants

Fruit Fly Trap

In order to build this experiment, you first need prey. We’re going to make a fruit fly trap to start your prey farm, and once this is established, then you can build the predator column. Here’s what you need to do to build the prey farm:

Download Student Worksheet & Exercises

Did you know that fruit flies don’t really eat fruit? They actually eat the yeast that growing on the fruit. Fruit flies actually bring the yeast with them on the pads of their feet and spread the yeast to the fruit so that they can eat it. You can tell if a fruit fly has been on your fuit because yeast has begun to spread on the skin.

When you have enough fruit flies to transfer to the predator-prey column, put the entire fruit fly trap in the refrigerator for a half hour to slow the flies down so you can move them.

If you find you’ve got way too many fruit flies, you might want to trap them instead of breed them. Remove the foil buckets every 4-7 days or when you see larvae on the fruit, and replace with fresh ones and toss the fruit away. Don’t toss the larvae in the trash, or you’ll never get rid of them from your trash area! Put them down the drain with plenty of water.

Predator-Prey Column

You can use carnivorous plants, small spiders, or praying mantises. If you use plants, choose venus flytraps, sundews, or butterworts and make sure your soil is boggy and acidic. You can add a bit of activated charcoal to the soil if you need to change the pH. Since the plants like warm, humid environments, keep the soil moist enough for water to fog up the inside on a regular basis. You know you’ve got too much moisture inside if you find algae on the plants and dirt. (If this happens, poke a couple of air holes.) Don’t forget to only use distilled water for the carnivorous plants!

Keep the column out of direct sunlight so you don’t cook your plants and animals.

Exercises

What shape is the head of the mantis?
How many eyes does a praying mantis have?
How else has the mantis head evolved to stalk their prey?
How does a praying mantis hold its food?
Do fruit flies eat fruit?
How do predators and prey change over time?

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Eco-Column

Sunday October 16, 2011

What grows in the corner of your windowsill? In the cracks in the sidewalk? Under the front steps? In the gutter at the bottom of the driveway? Specifically, how doe these animals build their homes and how much space do they need? What do they eat? Where do fish get their food? How do ants find their next meal?

These are hard questions to answer if you don’t have a chance to observe these animals up-close. By building an eco-system, you’ll get to observe and investigate the habits and behaviors of your favorite animals. This column will have an aquarium section, a decomposition chamber with fruit flies or worms, and a predator chamber, with water that flows through all sections. This is a great way to see how the water cycle, insects, plants, soil, and marine animals all work together and interact.

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Here’s what you need:

four (or more) 2-liter soda bottles, empty and clean and with caps
scissors
tape
razor with adult help
ruler
soil
water
plants or seeds
compost or organic/food scraps
spiders, snails, fruit flies, etc

Here’s what you do:

Download Student Worksheet & Exercises

You can easily incorporate the Water Cycle Column, the Terraqua Column, the Predator-Prey Column, Worm Column, and the Fruit Fly Trap into your Eco-Column. If you want to make your Eco-Column more permanent, seal it together with silicone sealant, making sure you have enough drainage holes and air holes in the right places first.

Exercises

What are parts of the eco system?

Give an example of each.

What do decomposers do?

How do fruit flies breed?

How does the precipitation funnel function in this eco column?

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Seeing Your Pulse

Saturday October 15, 2011

Your blood travels through your body very quickly. You probably already know that you can place your finger on certain points – like the radial artery in your wrist – and count the beats of your heart as it pumps blood throughout your body.

In this experiment, we will explore other ways to amplify your blood’s movement so that you can actually see a visual representation of it.

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Here’s what you need

1 lump of modeling clay or plastic putty
1 stopwatch
1 coffee stirrer straw
1 partner

Here’s what you do

Your radial artery in the wrist carries your blood from your heart down to your hand. Use your index and middle fingers to find your pulse in the radial artery on the inside of your left wrist.
Put a small, flat circle of clay on the spot where you found your radial artery’s pulse.
Push one end of the straw carefully into the clay or putty so that it’s standing up, perpendicular to your arm.
Using the stopwatch, record how many beats you see per minute by observing how many times the straw bounces.

What’s going on?

Your blood is pushed out of a chamber by the muscles of your heart and into your arteries, creating a force which is measurable. This is called your blood pressure. Systolic pressure is the resistance to outward blood flow through the arteries. The diastolic pressure is a measure of the blood flowing back to the heart to be oxygenated. Average blood pressure would be recorded as 120/80. Healthy blood pressure is important, since high blood pressure is a risk factor for many illnesses such as heart disease and stroke.

A few more random blood facts for you: there are 4 main types and they are A, B, AB and O. Oxygen binds to hemoglobin in your red blood cells, making an iron-rich compound. This makes the bright red color.

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How to Avoid the Dentist

Saturday October 15, 2011

Digestion involves the breakdown of what we consume into nutrients. The first step is mechanical digestion—chewing. After we mechanically break down the food with our teeth, we begin chemical digestion.

Teeth are small structures found in the mouths of vertebrates. They are calcified, meaning that they contain the element calcium, and are very distinctive based on the type of animal they are found in. Carnivores, or animals that eat meat, have sharp, pointy teeth for ripping and tearing prey. Plant-eating animals, known as herbivores, have larger flat teeth which they use to grind up the tough plant material they eat. Other animals, referred to as omnivores or generalists, eat both plant and animal material. As you might expect, these animals have both types of teeth. Humans fall into this category.

Humans and all other mammals are diphyodont, meaning we will have two sets of teeth in our lifetimes. Not all animals are this way. In fact, rodents and sharks both will continue to grow set after set of new teeth as they gnaw or bite their food. Other animals only have one set of teeth throughout their entire life.

In humans, the front teeth are called incisors. Next to the incisors are the sharp canines. To see how these two types of teeth are used, try a mini-experiment. Take a bite out of a banana and then take a bite of a carrot. Chew them as you would normally, and pay careful attention to what tooth is being used to chew. You’ll notice that for the softer banana, the incisors take the first bites. With the harder carrot, the canines do this job. In both cases, the chewing is done by the pre-molars, which are the teeth next to the canines, and the molars, the large, flat teeth closest to the back of your mouth.

Taking care of your teeth is very important. Brushing your teeth after every meal and flossing every day can go a long way in making sure your teeth stay healthy. If you don’t brush and floss, bacteria can build up over time, leading tartar and plaque on your teeth. If this continues, a small hole, or cavity, can form. Dentists can fill cavities, but this is generally something to be avoided if possible. Your gums can also become infected with bacteria if they are not cleaned. Bleeding gums can be one sign of gum disease. Serious dental procedures, such as extraction (the removal of a tooth) or a root canal are sometimes needed when dental care has been ignored for too long. The best thing to do is to avoid the problem to begin with by brushing, flossing, and visiting a dentist regularly.

What Happens to Food after You Put it in Your Mouth?

Saturday October 15, 2011

What is happening when we feel hungry? Or when we feel thirsty?

What we are feeling are hormones signaling our brain that we need food or water.

Hormones play a large role in our digestion process. They help maintain homeostasis by stimulating appetite, thirst, as well as many, many other bodily functions.

Digestion is the process of food (and drink) being broken down and absorbed. The mouth begins the digestion by breaking down food mechanically and chemically. Protein is digested in the stomach. The small intestine finishes the chemical digestion and absorption of food. The large intestine absorbs excess water from the waste and finally passes it through the anus.

What happens to those meals when they enter our mouths? There are the main things that happen:

Digestion: Digestion involves the breakdown of what we consume into nutrients. The first step is mechanical digestion—chewing. After we mechanically break down the food with our teeth, we begin chemical digestion. Chemical digestion breaks down what we eat and drink chemically. Chemical digestion is mostly accomplished by proteins called enzymes.
Absorption: After we’ve broken down the nutrients we need, we absorb them into our body. This step is called absorption.
Elimination: Lastly, we excrete solid and liquid waste.

Digestion begins in the mouth. In the mouth, the teeth digest food mechanically, and the saliva digests starches chemically. Enzymes are catalysts that make chemical reactions go faster. They are found at every important step of digestion. Amylase is found in our saliva, and it helps breaks down bread-like things (starches) into smaller sugar molecules. Pepsin helps us digest protein in our stomachs. Pancreatic lipase breaks down fats.

After the mouth, the food travels to the stomach through a narrow tube called the esophagus. The esophagus moves the ball of chewed and partially digested food into the stomach. Food is moved through the tube via muscle contractions. The muscle contractions start in the esophagus and end in the anus, moving in a wave called peristalsis. Peristalsis is the name of the movement of the muscle contractions moving the food through the tube.

Once in the stomach, the food is further chemically digested. The protein is digested with the enzyme pepsin. Pepsin, along with other chemicals such as hydrochloric acid (HCl) chemically digest the food. Water, salts, and simple sugars are absorbed through the walls of the stomach. The rest of the nutrients are absorbed after exiting the stomach.

The small intestine, about 7 ft long, has three parts. The large intestine takes the liquid waste from the small intestine, absorbs the excess water, and excretes the solid was through the anus. The large intestine is home to trillions of helpful bacteria. Although we often think of bacteria as harmful, most bacteria is helpful. The bacteria in our small intestines helps us digest food, and we provide the bacteria a place to live. Among other functions, the bacteria in our large intestines produce vitamins B12 and K, as well as break down poisons.

The liver is essential to digestion, and life. The liver detoxifies the blood, maintains the glucose balance, synthesizes proteins, and produces many chemicals needed for digestion.

Getting the right nutrients and getting fiber in your diet is extremely important. The nutrients keep your system running well, while fiber helps to move waste through your digestive system. If you do not get enough fiber you may become constipated; unable to pass waste.

Maintaining a healthy digestive system means a.) maintaining a healthy diet, and b.) taking care of any illnesses, allergies, or intolerances which arise.

What Do I Eat?

Saturday October 15, 2011

Eating and drinking are essential parts of our life. Part of maintaining a healthy lifestyle is making sure to eat and drink the right quantities of the six essential nutrients. Those nutrients are: protein, carbohydrates, lipids, vitamins, minerals, and water.

Does it mean to eat all vegetables? Does it mean to eat only meat? No. A healthy diet is a balanced diet. This is what MyPlate demonstrates. A balanced diet means getting the right amounts of nutrients. MyPlate guidelines are recommendations from the United States Department of Agriculture (USDA). Since 1958 the USDA has recommended a balanced diet in the form of the food pyramid. However, the pyramid proved to be too complicated for most Americans to efficiently use to create diets. In response, the USDA simplified its recommendations in 2011 into the MyPlate format.

We already know what a diet is—the sum of food and drink consumed. Now, what does it mean to have a healthy diet?

The specific advice of the USDA is:

Balance calorie intake.
Enjoy your food, but eat less.
Avoid oversized portions.
Eat certain foods.
Make half your plate fruit and vegetables.
Make at least half your grains whole grains.
Switch to fat-free or low fat (1%) milk.
Eat certain foods in moderation.
Compare sodium in foods like sodium, bread, and frozen meals—and choose the foods with lower numbers.
Drink water instead of sugary drinks.

What’s THAT called?

Friday October 14, 2011

If you’re like me, you like to know about the cool instruments doctors use when they poke and prod you in the standard office visit. I was always curious about what optometrists use during their eye exams. I found an instructional video that teaches optometrists about their tool for examining the fundus here:

Today, some people with vision problems choose to have surgery called LASIK. In this surgery, a laser changes the shape of the cornea correcting the vision problem. As a result, the person usually no longer needs to wear glasses or contacts. However, some problems are not correctable, even with LASIK.

Here’s a video on what it’s like to be blind:

If the vision problems can’t be corrected (as with blind, or no vision), how do people read? The Braille system was developed many years ago. Here’s a video that shows you how it works:

Eye Problems

Friday October 14, 2011

Do you or someone you know where glasses or contact lenses. Glasses and contacts are used to correct vision problems. The two most common eye problems are myopia and hyperopia, and each is fixed a different way.

Myopia is sometimes called nearsightedness. About one third of people have this problem. Myopia happens when the eye is too long. With eye too long, images seen are focused a little bit in front of the retina, instead of on the retina as they would be in a normal eye. People with myopia can see nearby objects clearly. Objects that are far away, however, look blurry. This can be corrected with a concave lens on glasses or contacts. “Concave” means that the lens curves inward, like the inside of a bowl. The concave lens helps focus light on the retina instead of in front of it, correcting the problem.

Hyperopia, which is also called farsightedness, affects about one fourth of people, is pretty much the opposite of myopia. In this disorder, the eye is too short, so images become focused behind the retina. As a result, people with hyperopia can see things clearly when they are far away, but not when they are close up. To correct hyperopia, a convex lens, which is a lens that curves out, like the outside of a bowl, is used in glasses or contacts.

Here’s a video that shows some of the latest technology in eye exams and what optometrists diseases can detect early on:

Some people suffer from both myopia and hyperopia. How can this be? It doesn’t seem possible that the eye could be too long and too short. The answer lies in the lens of your eye. You can think of the lens like a trampoline. As you jump up and down on the trampoline, it moves closer or further from the ground. The lens does a similar thing when you look at things closer together or further away. This makes the overall shape of the eye change slightly. As your trampoline gets older, the springs may begin to wear down, and it may become harder for the trampoline to move. The same thing happens with the lens in your eyes. As a result, many older people develop hyperopia. If these people already had myopia, they will need a lens that has both a concave and convex part. Bifocals are glasses that have these two parts.

Donating Blood

Friday October 14, 2011

If you’ve ever had a blood test, you may have wondered, perhaps as that needle was getting closer and closer, what exactly is the point of this? As it turns out, quite a lot. The standard blood test measures many things. There are also specific blood tests a doctor might order based on a person’s health history or a particular medication he or she is taking. A common blood test is the CBC, which stands for complete blood count. In this test, doctors can obtain counts of red blood cells (RBC) and white blood cells (WBC).

Healthy blood has 4.2 – 6.9 million RBC’s per cubic millimeter of blood and 43,000 108,000 WBC’s per cubic millimeter. That’s a lot of cells!

If a person has anemia, part of the CBC called the mean corpuscle volume (MCV) can help determine the cause. A CBC can also determine the amount of platelets in the blood, a very important number since platelets are needed for blood clotting. A range of 150,000 – 350,000 platelets per milliliter of blood is considered normal. Blood tests also commonly test for cholesterol levels. Cholesterol can clog the blood vessels, making it harder for blood to get around the body. This can lead to heart disease and heart attack. Healthy people generally have less than 225 milligrams of cholesterol per deciliter of blood, although the acceptable amount can increase as people age.

It is important to realize that there are some healthy people who will have blood tests results outside the “normal” range, and some people who are not healthy at all in spite of being within normal limits. This is why blood tests should be interpreted by a doctor or other medical professional. The thing to remember, however, is that blood tests are checking for important medical conditions. So even if it hurts a little for a moment, the test can do an awful lot of good.

Exercises for Digital Electronics

Thursday October 6, 2011

Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) You can also print these out and jot down your answers in your science notebook.
Click here for a printer-friendly version of the exercises and answers for Unit 14.

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1. What is a bit?

2. What is a nibble?

3. What is a byte?

4. What is a logic gate?

5. What is a truth table?

6. If we have a NAND gate with both inputs low, what is the output?

7. If we have an OR gate with both inputs low, what is the output?

8. If we have a NOR gate with both inputs low, what is the output?

9. What is a pull-down resistor?

10. What is a pull-up resistor?

11. How many gates are required to build a digital oscillator?

12. What is a SR Latch?

13. What is an inverter?

14. What is a D type Flip Flop?

15. What is switch bounce?

16. How can we solve switch bounce?

17. What is a seven segment display?

18. Why do we use seven segment displays?

19. What is a binary coded decimal counter?

20. What does a binary coded decimal to seven segment display IC do?

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Exercises for Basic Electronics

Thursday October 6, 2011

Click here for a printer-friendly version of the exercises and answers for Unit 14.

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1. What is a momentary contact switch?

2. What is an LED?

3. What is a piezo buzzer?

4. What is a relay?

5. What is a meter?

6. What is a potentiometer?

7. What is a photoresistor?

8. What is a 555 timer?

9. Using the formula R = V / I calculate the resistance value of a circuit with 12 volts and 1 amp of current.

10. Using the formula I = V / R, calculate the current a circuit is using with 12 volts and 100 ohms of resistance.

11. Using the formula E = I * R, calculate the voltage of a circuit that has a resistance of 100 ohms and is using 150 milliamps of current.

12. What happens if we connect an LED’s anode to ground and the cathode to positive voltage?

13. Why do we use a transformer in the audio experiments using the speaker?

14. What is a voltage divider?

15. What is a seven segment display?

16. What are the two types of transistors?

17. Why do we use transistors in electronics?

18. What is a voltage regulator?

19. What is the full name of an Op-Amp?

20. What does an Op-Amp do?

21. What is a bargraph?

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Answers to Exercises for Digital Electronics

Thursday October 6, 2011

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!

Answers:
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1. What is a bit?
A bit represents a logic 1 or a logic 0.

2. What is a nibble?
A nibble is a collection of four bits, also called a “four bit word”.

3. What is a byte?
A byte is 8 bits or two nibbles.

4. What is a logic gate?
A digital logic device that controls its output based on the values of the gate’s inputs.

5. What is a truth table?
A truth table shows us what a digital ICs output should be based on the combination of possible inputs.

6. If we have a NAND gate with both inputs low, what is the output?
High.

7. If we have an OR gate with both inputs low, what is the output?
Low.

8. If we have a NOR gate with both inputs low, what is the output?
High

9. What is a pull-down resistor?
A resistor that is used to force the voltage on a digital input or output to ground.

10. What is a pull-up resistor?
A resistor that is used to force the voltage on a digital input or output to positive voltage.

11. How many gates are required to build a digital oscillator?
2.

12. What is a SR Latch?
A basic digital memory circuit.

13. What is an inverter?
An inverter will output the opposite of what is being input. So if a 1 is on the input of an inverter then the inverter will output a 0.

14. What is a D type Flip Flop?
A memory circuit that can be set, cleared, and also have data clocked in. The D type flip flop also has two outputs, the first is equal to the stored data and the seconds is the inverted value of the stored data.

15. What is switch bounce?
The electrical noise a switch generates when closing or opening.

16. How can we solve switch bounce?
Capacitors can be used to absorb the “electrical noise” from a switch.

17. What is a seven segment display?
A group of seven LEDs arranged to form a pattern in the shape of the number eight.

18. Why do we use seven segment displays?
To translate computer data into information people can easily understand.

19. What is a binary coded decimal counter?
An IC that counts like we do, but stores the data in binary.

20. What does a binary coded decimal to seven segment display IC do?
It takes the BCD data from a counter (or other source) and converts it to the data a seven segment display needs to display numbers people can understand.

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Answers to Exercises for Basic Electronics

Thursday October 6, 2011

Answers:
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1. What is a momentary contact switch?
A switch that is only closed while being pressed.

2. What is an LED?
A diode that emits light.

3. What is a piezo buzzer?
A buzzer that converts electricity into sound.

4. What is a relay?
A device that turns on a secondary circuit when the primary circuits activates the relay.

5. What is a meter?
A device that is used to display electrical information so people can visualize the information.

6. What is a potentiometer?
An electrical device that can either divide a voltage and produce a variable voltage output or act as a variable resistor.

7. What is a photoresistor?
A photoresistor that varies its internal resistance based on the amount of light hitting the photoresistor’s sensor.

8. What is a 555 timer?
A integrated circuit that can be configured to produce a wide range of output frequencies.

9. Using the formula R = V / I calculate the resistance value of a circuit with 12 volts and 1 amp of current.
We know that the voltage is 12 volts and the current is 1 amp. So we divide 12 by 1 and that gives us the answer: 12. So the resistance is 12 Ohms. (12 = 12 / 1)

10. Using the formula I = V / R, calculate the current a circuit is using with 12 volts and 100 ohms of resistance.
We know that the voltage is 12 volts and the resistance is 100 ohms, so we divide 12 by 100 and that gives us the answer: 0.12, so the current is 0.12 Amps (0.12 = 12 / 100)

11. Using the formula E = I * R, calculate the voltage of a circuit that has a resistance of 100 ohms and is using 150 milliamps of current.
We know that the current is .15 amps and the resistance is 100 ohms. So we multiply .15 times 100 and that gives us the answer: 15, so the voltage is 15 volts (15 = .15 / 100)

12. What happens if we connect an LED’s anode to ground and the cathode to positive voltage?
Nothing, the LED will block the flow of current and it will remain off.

13. Why do we use a transformer in the audio experiments using the speaker?
To protect the circuit from excessive current draw, which can and probably will damage components.

14. What is a voltage divider?
A circuit that uses an electronic component (Resistors, Diodes, LEDs) to divide a voltage to a safe level for more sensitive electronic components.

15. What is a seven segment display?
A display that uses 7 LEDs to represent numbers and letters that people can understand.

16. What are the two types of transistors?
NPN (Negative-Positive-Negative) and PNP (Positive-Negative-Positive)

17. Why do we use transistors in electronics?
To protect low current circuits from other circuits that need higher current to operate. And also to amplify signals for devices that need higher strength to operate properly.

Monday October 3, 2011

Did you know that the DPDT (Double Throw Double Pole) switch can control up to four different devices? In this experiment we’ll see how the DPDT switch can be used to control multiple devices at the same time!

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Connect Two Switches in Series

Monday October 3, 2011

Now it’s time to listen in on some ants! Yes, I said ants! In this experiment we’ll be using two Operational Amplifiers, Op Amp for short, to build a super sensitive audio amplifier. This amplifier is so sensitive it can pick up very low sounds and amplify them so we can hear what’s going on.

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Add a Signal Strength Indicator

Monday October 3, 2011

But there’s no LED, and you know I love LEDs, so let’s add an LED to the super sensitive audio amplifier to include an LED. And, we’ll use the LED to indicate how strong the signal the microphone (earphone) is picking up.

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