Here’s a teleclass to get you started on learning about Thermodynamics.

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The next set of lessons will take you in more detail on each topic covered in the teleclass (and more)!

Click here to go to next lesson on Temperature.

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Temperature is a way of talking about, measuring, and comparing the thermal energy of objects. We use three different kinds of scales to measure temperature. Fahrenheit, Celsius, and Kelvin. (The fourth, Rankine, which is the absolute scale for Fahrenheit, is the one you’ll learn about in college.)
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Mr. Fahrenheit, way back when (18th century) created a scale using a mercury thermometer to measure temperature. He marked 0° as the temperature ice melts in a tub of salt. (Ice melts at lower temperatures when it sits in salt. This is why we salt our driveways to get rid of ice). To standardize the higher point of his scale, he used the body temperature of his wife, 96°.

As you can tell, this wasn’t the most precise or useful measuring device. I can just imagine Mr. Fahrenheit, “Hmmm, something cold…something cold. I got it! Ice in salt. Good, okay there’s zero, excellent. Now, for something hot. Ummm, my wife! She always feels warm. Perfect, 96°. ” I hope he never tried to make a thermometer when she had a fever. Just kidding, I’m sure he was very precise and careful, but it does seem kind of weird.

Over time, the scale was made more precise and today body temperature is usually around 98.6°F. Later, (still 18th century) Mr. Celsius came along and created his scale. He decided that he was going to use water as his standard. He chose the temperature that water freezes at as his 0° mark. He chose the temperature that water boils at as his 100° mark. From there, he put in 100 evenly spaced lines and a thermometer was born.

Last but not least Mr. Kelvin came along and wanted to create another scale. He said, I want my zero to be ZERO! So he chose absolute zero to be the zero on his scale.

Click here to go to next lesson on Absolute Zero.

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Absolute zero is the theoretical temperature where molecules and atoms stop moving. They do not vibrate, jiggle or anything at absolute zero. In Celsius, absolute zero is -273 ° C. In Fahrenheit, absolute zero is -459°F (or 0°R). It doesn’t get colder than that!

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Click here to go to next lesson on Thermometers.

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As you can see, creating the temperature scales was really rather arbitrary:  “I think 0° is when water freezes with salt.” “I think it’s just when water freezes.” “Oh, yea, well I think it’s when atoms stop!”  Many of our measuring systems started rather arbitrarily and then, due to standardization over time, became the systems we use today. So that’s how temperature is measured, but what is temperature measuring?

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Click here to go to next lesson on Thermal Energy.

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Temperature is measuring thermal energy which is how fast the molecules in something are vibrating and moving. The higher the temperature something has, the faster the molecules are moving. Water at 34°F has molecules moving much more slowly than water at 150°F. Temperature is really a molecular speedometer.   When something feels hot to you, the molecules in that something are moving very fast. When something feels cool to you, the molecules in that object aren’t moving quite so fast.

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Click here to go to next lesson on The Human Body.

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Have you ever wondered how an ice-cold glass of water gets waterdrops on the outside of the cup? Where does that water come from? Does it ease it’s way through the glass? Did someone come by and squirt the glass with water? No of course not.

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Some of the gaseous water molecules in the air came close enough to the cold glass to lose some molecular speed. Since they lost speed, they formed bonds between each other and liquefied. They condensed on the cold surface of the glass.

Imagine though, if you will, that you live several hundred years ago and the process of condensation wasn’t understood. You happen to be an inquisitive, highly perceptive, person (which of course you are) and you notice this film of water showing up on cold things. Water appearing out of apparently nowhere! You’d be pretty amazed wouldn’t you?!?

Personally, I still find it amazing that every time I pick up a cold can of soda there are molecular interactions happening right in front of my eyes! This is why science is so wonderful. It provides the skills to see these amazing things and the skills to investigate and perhaps understand them.

Crazy Temperatures

Here’s an experiment you can do to baffle your senses: Fill one glass with hot water (not boiling), another with ice water, and a third with room temperature water. Place a finger in the hot water and a finger in the ice cold water for a minute or two. Then stick both fingers in the room temperature cup.

How does that feel?

Did it seem that each finger detected a different temperature when placed in the room temperature cup? Weird! So what gives?

Materials:

• 3 cups of water (see video)
• your hands

Download Student Worksheet & Exercises

Your skin contains temperature sensors that work by detecting the direction heat flow (in or out of your body), not temperature directly. These sensors change temperature depending on their surroundings. So when you heated up one finger, and then placed it in cooler water, the heat flowed out of your body, telling your brain it was getting cooler. The ice water finger was detecting a heat flow into your body… and presto! You have one confused brain.

In order for heat to flow, you need to have a temperature difference. But why then do the metal legs of a table feel colder than the wood tabletop when both are at the same room temperature? The metal will feel colder because heat flows away from your skin faster into the metal than the wood. We’ll talk about heat capacity in a later experiment, but this is why scientists had to invent the thermometer, because the human body isn’t designed to detect temperature, only heat flow.

Click here to go to next lesson on Changing Molecular Speeds.

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You may have asked yourself the question, “So, if everything is made of molecules, and these molecules are often speeding up and slowing down… what happens to the stuff these molecules are made of if they change speed a lot? Will my kitchen table start vibrating across the room if the table somehow gets too hot?” No, it’s pretty unlikely that your table will begin jumping around the room, no matter how hot it gets. However, some interesting things do happen when molecules change speeds.

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Click here to go to next lesson on States of Matter.

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Is it warmer upstairs or downstairs? If you’re thinking warm air rises, then it’s got to be upstairs, right? If you’ve ever stood on a ladder inside your house and compared it to the temperature under the table, you’ve probably felt a difference.

So why is it cold on the mountain and warm in the valley? Leave it to a science teacher to throw in a wrench just when you think you’ve got it figured out. Let’s take a look at whether hot air or cold air takes up more space. Here’s what you do:

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Materials:

• water
• plastic bottle
• balloon
• stove top and saucepan or the setup in the video

Download Student Worksheet & Exercises

1. Pour a couple of inches of water into an empty soda bottle and cap with a 7-9″ balloon. You can secure the balloon to the bottle mouth with a strip of tape if you want, but it usually seals tight with just the balloon itself.

2. Fill a saucepan with an inch or two of water, and add your bottle. Heat the saucepan over the stove with adult help, keeping a close eye on it. Turn off the heat when your balloon starts to inflate. Since water has a high heat capacity, the water will heat before the bottle melts. (Don’t believe me? Try the Fire-Water Balloon Experiment first to see how water conducts heat away from the bottle!)

3. When you’re finished, stick the whole thing in the freezer for an hour. What happened to the balloon?

What’s going on? So now what do you think? Does the same chunk of air take up more or less space when it’s hot? Cold? When you heat air, it expands because the air molecules move around a lot more when you add energy. The molecules zip around and wiggle like crazy, bouncing off each other more often than when they are cooler.

Getting back to our original question, the upstairs in a house is warmer because the pockets of warm air rise because they are less dense than cool air. The more the molecules move around, the more room they need, and the further they get spaced out. Think of a swimming pool and a piece of aluminum foil. If you place a sheet of foil in the pool, it floats. If you take the foil and crumple it up, it sinks. The more compactly you squish the molecules together, the more dense it becomes. You can read more about density in Unit 3.

As for why mountains and valleys are opposite, it has to do with the Earth being a big massive ball of warm rock which heats up the lower atmosphere in addition to winds blowing on mountains and changes in pressure as you gain altitude… in a nutshell, it’s complicated! What’s important to remember is that the Earth system is a lot bigger than our bottle-saucepan experiment, and can’t be represented in this way.

Exercises

1. Draw a group of molecules at a very cold temperature in the space below. Use circles to represent each molecule.
2. True or False: A molecule that heats up will move faster.
   1. True
   2. False
3. True or False: A material will be less dense at lower temperatures.
   1. True
   2. False

Click here to go to next lesson on Melting and Evaporation.

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Indoor Rain Clouds

Making indoor rain clouds demonstrates the idea of temperature, the measure of how hot or cold something is. Here’s how to do it:

Take two clear glasses that fit snugly together when stacked. (Cylindrical glasses with straight sides work well.)

Fill one glass half-full with ice water and the other half-full with very hot water (definitely an adult job – and take care not to shatter the glass with the hot water!). Be sure to leave enough air space for the clouds to form in the hot glass.

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Place the cold glass directly on top of the hot glass and wait several minutes. If the seal holds between the glasses, a rain cloud will form just below the bottom of the cold glass, and it actually rains inside the glass! (You can use a damp towel around the rim to help make a better seal if needed.)

Materials:

• glass of ice water
• glass of hot water (see video)
• towel
• adult help

Download Student Worksheet & Exercises

Bottling Clouds

On a stormy, rainy afternoon, try bottling clouds — using the refrigerator! Here’s what you do: Place an empty, clean 2-liter soda bottle in the fridge overnight. Take it out and get an adult to light a match, letting it burn for a few seconds, then drop it into the bottle. Immediately cap the bottle and watch what happens (you should see smoke first, then clouds forming inside). Squeeze the sides of the bottle. The clouds should disappear. When you release the bottle, the clouds should reappear. Materials:

• 2L soda bottle
• rubbing alcohol
• bicycle pump
• car tire valve (drill a 1/2 inch hole through a 2L soda bottle cap and pull the valve gently through with pliers)

Advanced Idea: You can substitute rubbing alcohol and a bicycle pump for the matches to make a more solid-looking cloud.  Swirl a bit of rubbing alcohol around inside the bottle, just enough to coat the insides, and then pour it out.  Cap your bottle with a rubber stopper fitted with a needle valve (so the valve is poking out of the bottle), and apply your pump.  Increase the pressure inside the bottle (keep a firm hand on the stopper or you’ll wind up firing it at someone) with a few strokes and pull out the stopper quickly.  You should see a cloud form inside.

What’s going on? Invisible water vapor is all around us, all the time, but they normally don’t stick together. When you squeezed the sides of the bottle, you increased the pressure and squeezed the molecules  together.  Releasing the bottle decreases the pressure, which causes the temperature to drop. When it cools inside, the water molecules stick to the smoke molecules, making a visible cloud inside your bottle.

Did you know that most drops of water actually form around a dust particle?  Up in the sky, clouds come together when water vapor condenses into liquid water drops or ice crystals. The clouds form when warm air rises and the pressure is reduced (as you go up in altitude). The clouds form at the spot where the temperature drops below the dew point.

The alcohol works better than the water because it evaporates faster than water does, which means it moves from liquid to vapor more easily (and vividly) than regular old water.

Questions to ask:

• How many times can you repeat this?
• Does it matter what size the bottle is?
• What if you don’t chill the bottle?
• What if you freeze the bottle instead?

Exercises

1. Which combination made it rain the best? Why did this work?
2. Draw your experimental diagram, labeling the different components:
3. Add in labels for the different phases of matter. Can you identify all three states of matter in your experiment?

Click here to go to next lesson on Condensation and Freezing.

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This spooky idea takes almost no time, requires a dime and a bottle, and has the potential for creating quite a stir in your next magic show.  The idea is basically this: when you place a coin on a bottle, it starts dancing around. But there’s more to this trick than meets the scientist’s eye.

Here’s how you do it:

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Materials:

• coin
• freezer
• plastic bottle (NOT glass)

Download Student Worksheet & Exercises

Remove the cap of an empty plastic water or soda bottle and replace it with a dime and stick the whole things upright in the freezer overnight. First thing in the morning, take it out and set it on the table. What happens?

Attention:  Magicians

If you’re a budding magician, here’s how to modify this experiment to use in your next show.  Get a glass container of soda and stick it in the coldest part of your fridge overnight. I know they are getting harder to find these days, but the glass will keep its temperature longer than plastic and enable you to do this trick.  In a pinch, you can refill a cleaned glass bottle from a previous use if you can’t locate a fresh glass soda bottle.

As soon as you’re ready to do your trick (practice first!), take it out of the fridge (have it in an ice chest if you’re on stage) and chug the whole thing. (You can ask your audience for help on this – you just want an empty cold bottle for the next part.)

When the bottle is empty but still cold, cap it with a wet dime. Place both hands on the bottle while you “wax eloquent” (make up an engaging story, like “North Winds, come have a taste of soda…”) but be sure to keep your hands on the bottle to warm it up. In about 20 seconds or so, the dime will click up and down, dancing around mysteriously.  Keep your hands on the bottle for another 20 seconds or so, and then set it gently on the table with it still dancing, and you’ll find it dancing right on without your hands being there.

How does that work? Was the bottle really empty when you placed it in the freezer? Actually, no… it had air inside of it. The air in the bottle shrank down a bit as it cooled, allowing more air to go into the bottle. When you remove the bottle from the freezer and cap it with the coin, you now have a bottle with more air in it than you started. The air warms and expands, pushing the excess air out the top, making the coin dance. Learn more about air with this Air Expands experiment.

Variations to try:

• Is a plastic bottle or glass bottle better for this experiment?
• What if you get the coin wet first?
• Does a cold or warm coin work better?
• What about a penny? Quarter?
• Does the size of the bottle matter?

Exercises

1. When a gas turns into a liquid, this is called:
   1. Convection
   2. Conduction
   3. Absorption
   4. Condensation
2. When water boils, what happens to the bonds between its molecules?
3. What is the best way to describe how the bonds between water molecules behave when in a liquid state?
   1. Solid bridges
   2. Rubber bands
   3. No bonds
   4. Brittle like chalk
4. The crystalline shape of a solid is referred to as:
   1. a matrix
   2. a vortex
   3. a crystal
   4. a cube

Click here to go to next lesson on What are clouds?

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Clouds are made of hundreds of billions of tiny little droplets of liquid water that have condensed onto particles of some sort of dust. Now let’s turn the heat down a bit more and see what happens. As the temperature drops and the molecules continue to slow, the bonds between the molecules can pull them together tighter and tighter.

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Eventually the molecules will fall into a matrix, a pattern, and stick together quite tightly. This would be the solid state. The act of changing from a liquid to a solid is called freezing and the temperature at which it changes is called (say it with me now) freezing point.

Think about this for a second – is the freezing point and melting point of an object at the same temperature? Does something go from solid to liquid or from liquid to solid at the same temperature? If you said yes, you’re right! The freezing point of water and the melting point of water are both 32° F or 0° C. The temperature is the same. It just depends on whether it is getting hotter or colder as to whether the water is freezing or melting. The boiling and condensation point is also the same point.

Now I’m going to mess things up a little bit. Substances can change state at temperatures other than their different freezing or boiling points. Many liquids change from liquid to gas and from gas to liquid relatively easily at room temperatures. And, believe it or not, solids can change to liquids and even gases and vice versa at temperatures other than the usual melting, freezing, or boiling points. So what’s the point of the points?

Click here to go to next lesson on Changing States at Unusual Places.

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At a substance’s boiling, freezing, etc, points, all of the substance must change to the next state. The condition of the bonds cannot remain the same at that temperature. For example, at 100° C water must change from a liquid to a gas. That is the speed limit of liquid water molecules. At 100° C the liquid bonds can no longer hold on and all the molecules convert to gas.

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Click here to go to next lesson on Heat.

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Believe it or not, the concept of heat is really a bit tricky. What we call heat in common language, is really not what heat is as far as physics goes.

Heat, in a way, doesn’t exist. Nothing has heat. Things can have a temperature. They can have a thermal energy but they can’t have heat. Heat is really the transfer of thermal energy. Or, in other words, the movement of thermal energy from one object to another.

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If you put an ice cube in a glass of lemonade, the ice cube melts. The thermal energy from your lemonade moves to the ice cube. Increasing the temperature of the ice cube and decreasing the temperature of your lemonade. The movement of thermal energy is called heat. The ice cube receives heat from your lemonade. Your lemonade gives heat to the ice cube. Heat can only move from an object of higher temperature to an object of lower temperature.  

Click here to go to next lesson on Heat goes from hot to cold.

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If you’ve completed the Soaking Up Rays experiment, you might still be a bit baffled as to why there’s a difference between black and white. Here’s a great way to actually “see” radiation by using liquid crystal thermal sheets.

You’ll need to find a liquid crystal sheet that has a temperature range near body temperature (so it changes color when you warm it with your hands.)

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The liquid crystal sheet is temperature-sensitive. When the sheet received heat from the bulb, the temperature goes up and changes color. The plastic sheets remain black except for the temperature range in which they display a series of colors that reflect the actual temperature of the crystal.

Materials:

• hands
• Thermal paper (AKA: Liquid Crystal Sheet)
• Incandescent light bulb (or sunny day)
• Silver highlighter or aluminum foil

1. Color half of the back side of the thermal paper (the side that doesn’t change color) with the highlighter (or cover half of it with foil).

2. Hold it in a position where you can easily see the color-changing side while keeping the light source on the back side.

3. Which side changes color? Is there a difference between the silver and black halves?

You’ll notice that the black half almost immediately changes color, while the silver side stays black.  The silver coating reflects the heat, keeping it cool. The black side absorbs the heat and raises its temperature.

Why do liquid crystals change color with temperature? Your liquid crystal sheet is not just one sheet, but a stack of several sheets that are slightly offset from each other. The distance between each layer changes as the sheet warms up – the hotter the temperature, the closer the stacks twist together. The color they emit depends on the distance between the sheets.

The molecules that make up the sheets are long and thin, like hot dogs. When the sheets are cooler, these molecules move around less and don’t twist up as much, which corresponds to reflecting back a redder light.  When the temperature rises, the molecules move around more and twist together, and they reflect a bluer light. When the liquid crystal sheet is black, all the light is absorbed (no light gets reflected).

Click here to go to next lesson on Heat Capacity.

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Now let’s take explore how, even though heat can move from one object to another, it doesn’t necessarily mean that the temperature of the objects will change. You may ask, “What? Heat can move from one object to another without temperature changing one little bit?!?!” We’re going to take a look at one of the ways heat can move while the thermometer doesn’t.

When things change phase (change from solid to liquid or liquid to gas or… well, you get the picture) the temperature of those objects don’t change. If you were able to take the temperature of water as it changed from a solid (ice) to a liquid you would notice that the temperature of that piece of ice will stay at about 32° F until that piece of ice was completely melted. The temperature would not increase at all. Even if that ice was in an oven, the temperature would stay the same. Once all the solid ice had disappeared, then you would see the temperature of the puddle of water increase.

By the way, as the ice is melting, from where is heat being transferred? Heat is being transferred, by conduction, from the air.

One key distinction is that objects don’t contain heat, but they contain energy. Heat is the transfer of energy from from one object to another, or from one system to another, like a hot cup of coffee to the cool ambient air. Heat can change the temperature of objects when it transfers the energy. In the example with the coffee cup, it lowered the temperature of the coffee.

Imagine putting a sponge under a slowly running faucet. The sponge would continue to fill with water until it reached a certain point and then water started to drip from it. You could say that the sponge had a water capacity. It could hold so much water before it couldn’t hold any more and the water started dripping out.

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Heat capacity is how much heat an object can absorb before it increases in temperature. It’s often used interchangeably with “specific heat capacity”, but in reality it’s a little different.

Click here to go to next lesson on Specific Heat Capacity.

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Specific heat capacity is how much heat energy a mass of a material must absorb before it increases 1°C. It’s how much heat is needed to raise the temperature of 1 gram of the material. Heat Capacity is how much heat is required to raise the temperature. The units of heat capacity are J per Kelvin, whereas for specific heat capacity, the units are J per (gram-K).

Each material has its own specific heat. The higher a material’s specific heat, the more heat it must absorb before it increases in temperature.  Water is unique in that it has a very large specific heat. Liquid water’s specific heat is over 4 which is very high. In comparison, granite is 0.8, aluminum is 0.9, rubbing alcohol is 2.4 and gold is 0.1.

To get the same amount of rubbing alcohol and liquid water to increase the same amount of temperature, you would need to pump about twice the amount of heat into the water. To get the same amount of gold and liquid water to increase the same amount of temperature, you would need to pump 40 times the amount of heat into the water!

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Click here to go to next lesson on Fire Water Balloon.

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If you’ve ever had a shot, you know how cold your arm feels when the nurse swipes it with a pad of alcohol. What happened there? Well, alcohol is a liquid with a fairly low boiling point. In other words, it goes from liquid to gas at a fairly low temperature. The heat from your body is more then enough to make the alcohol evaporate.

As the alcohol went from liquid to gas it sucked heat out of your body. For things to evaporate, they must suck in heat from their surroundings to change state. As the alcohol evaporated you felt cold where the alcohol was. This is because the alcohol was sucking the heat energy out of that part of your body (heat was being transferred by conduction) and causing that part of your body to decrease in temperature.

As things condense (go from gas to liquid state) the opposite happens. Things release heat as they change to a liquid state. The water gas that condenses on your mirror actually increases the temperature of that mirror. This is why steam can be quite dangerous. Not only is it hot to begin with, but if it condenses on your skin it releases even more heat which can give you severe burns. Objects absorb heat when they melt and evaporate/boil. Objects release heat when they freeze and condense.

Do you remember when I said that heat and temperature are two different things? Heat is energy – it is thermal energy. It can be transferred from one object to another by conduction, convection, and radiation. We’re now going to explore heat capacity and specific heat. Here’s what you do:

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You Need:

• Balloon
• Water
• Matches, candle, and adult help
• Sink

Download Student Worksheet & Exercises

1. Put the balloon under the faucet and fill the balloon with some water.

2. Now blow up the balloon and tie it, leaving the water in the balloon. You should have an inflated balloon with a tablespoon or two of water at the bottom of it.

3. Carefully light the match or candle and hold it under the part of the balloon where there is water.

4. Feel free to hold it there for a couple of seconds. You might want to do this over a sink or outside just in case!

So why didn’t the balloon pop? The water absorbed the heat! The water actually absorbed the heat coming from the match so that the rubber of the balloon couldn’t heat up enough to melt and pop the balloon. Water is very good at absorbing heat without increasing in temperature which is why it is used in car radiators and nuclear power plants. Whenever someone wants to keep something from getting too hot, they will often use water to absorb the heat.

Think of a dry sponge. Now imagine putting that sponge under a slowly running faucet. The sponge would continue to fill with water until it reached a certain point and then water started to drip from it. You could say that the sponge had a water capacity. It could hold so much water before it couldn’t hold any more and the water started dripping out. Heat capacity is similar. Heat capacity is how much heat an object can absorb before it increases in temperature. This is also referred to as specific heat. Specific heat is how much heat energy a mass of a material must absorb before it increases 1°C.

Exercises Answer the questions below:

1. What is specific heat?
   1. The specific amount of heat any object can hold
   2. The amount of energy required to raise the temperature of an object by 1 degree Celsius.
   3. The type of heat energy an object emits
   4. The speed of a compound’s molecules at room temperature
2. Name two types of heat energy:
3. What type (or types) of heat energy is at work in today’s experiment?
4. True or False: Water is poor at absorbing heat energy.
   1. True
   2. False

Click here to go to next lesson on How much energy does a candy bar have?

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How much energy does a candy bar have? How much energy does a candy bar have? If you flip it over and read the nutritional information on the back, you can figure it out with a little help from the video below:

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Click here to go to next lesson on Heat Flow.

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Let’s learn how to calculate the heat flow based solely on temperature readings from a thermometer (this is going to be important later in this lab):

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Click here to go to next lesson on Heat and States of Matter.

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Heat can also change the state of matter. When an ice cube melts into a liquid puddle, it remains at the same temperature until the phase change is complete, and only then does the temperature begin to rise, even though heat was added throughout the entire process. The thermometer reading will stay on the same temperature reading until the ice is completely melted.

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Click here to go to next lesson on Sublimation.

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Carbon dioxide goes straight from a solid to a gas, which is called “sublimation”. It totally skips going through the liquid phase! How do you handle the transition from a solid block to a gas cloud? Here’s how:

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Did you know that eating a single peanut will power your brain for 30 minutes? The energy in a peanut also produces a large amount of energy when burned in a flame, which can be used to boil water and measure energy.

Click here to go to next lesson on Heat Energy of a Peanut.

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This experiment is for advanced students. Did you know that eating a single peanut will power your brain for 30 minutes? The energy in a peanut also produces a large amount of energy when burned in a flame, which can be used to boil water and measure energy.

Peanuts are part of the bean family, and actually grows underground (not from trees like almonds or walnuts).  In addition to your lunchtime sandwich, peanuts are also used in woman’s cosmetics, certain plastics, paint dyes, and also when making nitroglycerin.

What makes up a peanut?  Inside you’ll find a lot of fats (most of them unsaturated) and  antioxidants (as much as found in berries).  And more than half of all the peanuts Americans eat are produced in Alabama. We’re going to learn how to release the energy inside a peanut and how to measure it.

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Materials:

• raw peanuts
• chemistry stand with glass test tube and holder (watch video)
• flameproof surface (large ceramic tile or cookie sheet)
• paper clip
• alcohol burner or candle with adult help
• fire extinguisher

Download Student Worksheet & Exercises

What’s Going On? There’s chemical energy stored inside a peanut, which gets transformed into heat energy when you ignite it. This heat flows to raise the water temperature, which you can measure with a thermometer.  You should find that your peanut contains 1500-2100 calories of energy!  Now don’t panic…  this isn’t the same as the number of calories you’re allowed to eat in a day.  The average person aims to eat around 2,000 Calories (with a capital “C”).  1 Calorie = 1,000 calories.  So each peanut contains 1.5-2.1 Calories of energy (the kind you eat in a day). Do you see the difference?

But wait… did all the energy from the peanut go straight to the water, or did it leak somewhere else, too?  The heat actually warmed up the nearby air, too, but we weren’t able to measure that. If you were a food scientist, you’d use a nifty little device known as a bomb calorimeter to measure calorie content.  It’s basically a well-insulated, well-sealed device that catches nearly all the energy and flows it to the water, so you get a much more accurate temperature reading. (Using a bomb calorimeter, you’d get 6.1-6.8 Calories of energy from one peanut!)

How do you calculate the calories from a peanut?

Let’s take an example measurement.  Suppose you measured a temperature increase from 20 °C to 100 °C for 10 grams of water, and boiled off 2 grams.  We need to break this problem down into two parts – the first part deals with the temperature increase, and the second deals with the water escaping as vapor.

The first basic heat equation is this:

Q = m c T

Q is the heat flow (in calories)
m is the mass of the water (in grams)
c is the specific heat of water (which is 1 degree per calorie per gram)
and T is the temperature change (in degrees)

So our equation becomes: Q = 10 * 1 * 80 = 800 calories.

If you measured that we boiled off 2 grams of water, your equation would look like this for heat energy:

Q = L m

L is the latent heat of vaporization of water (L= 540 calories per gram)
m is the mass of the water (in grams)

So our equation becomes: Q = 540 * 2 = 1080 calories.

The total energy needed is the sum of these two:

Q = 800 calories + 1080 calories = 1880 calories.

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.
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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 

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

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Click here to go to next lesson on Thermostat.

If you can remember thermostats before they went ‘digital’, then you may know about bi-metallic strips – a piece of material made from of two strips of different metals which expand at different rates as they are heated (usually steel and copper). The result is that the flat strip bends one way if heated, and in the opposite direction if cooled.

Normally, it takes serious skill and a red-hot torch to stick two different metals together, but here’s a homemade version of this concept that your kids can make using your freezer.  Here what you do:

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Materials:

• foil wrapper from a stick of gum or candy bar
• index card
• scissors
• tape

Since gum wrappers are paper on one side and foil on the other, you can use one to make your own bi-metallic strip. Flatten out the wrapper into a sheet and find a way fasten the wrapper so it sits upright on an index card (we used the bubble gum itself as the adhesive). Stick it in the freezer overnight and check it in the morning! Where can you place it to flex the other direction?

How does that work? A bimetallic strip is a stack of two metals stuck together. The metal with the higher expansion is on the outer side of the curve when the strip is heated and on the inner side when cooled. The bi-metallic strip was invented by the eighteenth century clockmaker John Harrison to compensate for temperature-induced changes his clock springs.

Click here to go to next lesson on Triple Point.

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The triple point is where a molecule can be in all three states of matter at the exact same time, all in equilibrium. Imagine having a glass of liquid water happily together with both ice cubes and steam bubbles inside, forever! The ice would never melt, the liquid water would remain the same temperature, and the steam would bubble up. In order to do this, you have to get the pressure and temperature just right, and it’s different for every molecule.

The triple point of mercury happens at -38^oF and 0.000000029 psi. For carbon dioxide, it’s 75psi and -70^oF. So this isn’t something you can do with a modified bike pump and a refrigerator.

However, the triple point of water is 32^oF and 0.089psi. The only place we’ve found this happening naturally (without any lab equipment) is on the surface of Mars.

Because of these numbers, we can get water to boil here on Earth while it stays at room temperature by changing the pressure using everyday materials. (If you have a vacuum pump, you can have the water boil at the freezing point of 32^oF.)

Here’s what you need to do:

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Materials:

• plastic syringe (no needle)
• room temperature water

Bonus Idea: Do this experiment first with water, then with carbonated water.

Why does that work? How did you get the pressure to decrease? Easy – when you pulled on the plunger and increased the volume inside the syringe. Since your finger covered the hole, no additional air was allowed in when you did this (which is why it was probably a little tough to do), so the number of molecules inside the syringe stayed the same, but the space they had to wiggle around got a lot bigger, meaning that the pressure decreased.

The air inside the syringe isn’t just plain old air… it has water vapor inside, too. And that’s not all – the water from your sink isn’t just plain old water, it has air bubbles mixed in with it. When you brought down the pressure (by pulling the plunger), you are forcing the air bubbles to come out of the water, which makes it boil. When you shove the plunger back in and increase the pressure, you’ll find that the air bubbles mix back into the water and disappears.

Did you try the soda water yet? Soda has carbon dioxide already mixed in for you, which is under pressure. You can release this pressure by opening the bottle (you’ll hear a PSSST!), which is the carbon dioxide bubbles coming out of the soda. Go ahead and try that now before reading further…

When you place the soda water into the syringe and decrease the pressure, the carbon dioxide comes out quickly Try tapping the syringe to make all the tiny bubbles combine into one larger bubble. When you increase the pressure (push the plunger back in), some of the bubbles will redissolve back into the soda.

If you’ve ever had a glass of hot water suddenly erupt in an explosion of bubbles, you’ve experienced superheated water (water that’s above it’s normal boiling point) that hasn’t been able to form bubbles yet. By adding a tea bag or simply just jiggling it around is usually enough to cause the bubbles to start, which often splatters HOT HOT water everywhere. (This isn’t something you want to try without adult help.)

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Click here to go to next lesson on Conduction.

In our example of the ice and the lemonade, it would work like this. The lemonade has a higher temperature than the ice. (The molecules are moving faster than the ice molecules.)

The faster moving molecules of the lemonade would transfer heat to the ice causing the ice molecules to move faster (increase temperature) and eventually change from solid to liquid.

In turn, since the faster moving molecules of the lemonade moves energy (transfers heat) to the ice, they slow down. This causes the temperature of your drink to decrease and that is what makes your lemonade nice and cold. Heat can be transferred in three different ways: conduction, convection and radiation.

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Let’s start with conduction. Heat is transferred through conduction the same way pool balls are scattered around a table in the opening break. On a pool table, one ball crashes into another ball which crashes into another ball speeding the balls up and moving them around the table.

Heat transferred from one object to another through conduction does the same thing. The molecules near the heat source (candle, stove, etc.) begin moving faster (their temperature increases).

Click here to go to next lesson on Convection.

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When something feels hot to you, the molecules in that something are moving very fast. When something feels cool to you, the molecules in that object aren’t moving quite so fast. Believe it or not, your body perceives how fast molecules are moving by how hot or cold something feels. Your body has a variety of antennae to detect energy. Your eyes perceive certain frequencies of electromagnetic waves as light. Your ears perceive certain frequencies of longitudinal waves as sound. Your skin, mouth and tongue can perceive thermal energy as hot or cold. What a magnificent energy sensing instrument you are!

Let’s find out how to watch the hot and cold currents in water. Here’s what you need to do:

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Materials:

• two bottles of water
• food coloring
• bathtub or sink
• index card or business card

You need:

Two empty bowls (or water bottles)
Food coloring
Hot water (Does not need to be boiling.)
Cold water

1. Put about the same amount of water into two bowls. One bowl should be filled with hot water from the tap. If you’re careful, you can put it in the microwave to heat it up but please don’t hurt yourself. The other bowl should have cold water in it. If you’re using water bottles, pour the hot and cold water into each bottle.

2. Let both bowls sit for a little bit (a minute or so) so that the water can come to rest.

3. Put food coloring in both bowls (or bottles) and watch carefully.

The food coloring should have spread around faster in the hot water bowl than in the cold water bowl. Can you see why? Remember that both bowls are filled with millions and millions of molecules. The food coloring is also bunches of molecules. Imagine that the molecules from the water and the molecules from the food coloring are crashing into one another like the beans on the plate. If one bowl has a higher temperature than the other, does one bowl have faster moving molecules? Yes, the higher temperature means a higher thermal energy. So the bowl with the warmer water has faster moving molecules which crash more and harder with the food coloring molecules, spreading them faster around the bowl.

If you’re using a bottle, you can do an extra step: For bottles, place a business card over the cold bottle and invert the cold bottle over the hot. Remove card.

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Click here to go to next lesson on Convection Currents.

Every time I’m served a hot bowl of soup or a cup of coffee with cream I love to sit and watch the convection currents. You may look a little silly staring at your soup but give it a try sometime!

Convection is a little more difficult to understand than conduction. Heat is transferred by convection by moving currents of a gas or a liquid. Hot air rises and cold air sinks. It turns out, that hot liquid rises and cold liquid sinks as well.

Room heaters generally work by convection. The heater heats up the air next to it which makes the air rise. As the air rises it pulls more air in to take its place which then heats up that air and makes it rise as well. As the air get close to the ceiling it may cool. The cooler air sinks to the ground and gets pulled back near the heat source. There it heats up again and rises back up.

This movement of heating and cooling air is convection and it can eventually heat an entire room or a pot of soup. This experiment should allow you to see convection currents.

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You need:

• A pot
• A stove with adult help
• Pepper
• Ice cubes
• Food Coloring (optional)

1. Fill the pot about half way with water.

2. Put about a teaspoon of pepper into the water.

3. Put the pot on the stove and turn on the stove (be careful please).

4. Watch as the water increases in temperature. You should see the pepper moving. The pepper is moving due to the convection currents. If you look carefully you many notice pepper rising and falling.

5. Put an ice cube into the water and see what happens. You should see the pepper at the top of the water move towards the ice cube and then sink to the bottom of the pot as it is carried by the convection currents.

6. Just for fun, put another ice cube into the water, but this time drop a bit of food coloring on the ice cube. You should see the food coloring sink quickly to the bottom and spread out as it is carried by the convection currents.

Did you see the convection currents? Hot water rising in some areas of the pot and cold water sinking in other areas of the pot carried the pepper and food coloring throughout the pot. This rising and sinking transferred heat through all the water causing the water in the pot to increase in temperature.

Heat was transferred from the flame of the stove to the water by convection. More accurately, heat was transferred from the flame of the stove to the metal of the pot by conduction and then from the metal of the pot throughout the water through convection.

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Click here to go to next lesson on Radiation.

Heat is transferred by radiation through electromagnetic waves. Remember, when we talked about waves and energy? Well, heat can be transferred by electromagnetic waves. Energy is vibrating particles that can move by waves over distances right? Well, if those vibrating particles hit something and cause those particles to vibrate (causing them to move faster/increasing their temperature) then heat is being transferred by waves. The type of electromagnetic waves that transfer heat are infra-red waves. The Sun transfers heat to the Earth through radiation.

If you hold your hand near (not touching) an incandescent light bulb until you can feel heat on your hand, you’ll be able to understand how light can travel like a wave. This type of heat transfer is called radiation.

Now don’t panic. This is not a bad kind of radiation like you get from x-rays. It’s infra-red radiation. Heat was transferred from the light bulb to your hand. The energy from the light bulb resonated the molecules in your hand. (Remember resonance?) Since the molecules in your hand are now moving faster, they have increased in temperature. Heat has been transferred! In fact, an incandescent light bulb gives off more energy in heat then it does in light. They are not very energy efficient.

Now, if it’s a hot sunny day outside, are you better off wearing a black or white shirt if you want to stay cool? This experiment will help you figure this out:

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You need:

• 2 ice cubes, about the same size.
• A white piece of paper
• A black piece of paper
• A sunny day

Download Student Worksheet & Exercises

1. Put the two pieces of paper on a sunny part of the sidewalk.

2. Put the ice cubes in the middle of the pieces of paper.

3. Wait.

What you should eventually see, is that the ice cube on the black sheet of paper melts faster then the ice cube on the white sheet. Dark colors absorb more infra-red radiation then light colors. Heat is transferred by radiation easier to something dark colored then it is to something light colored and so the black paper increased in temperature more then the white paper.

So, to answer the shirt question, a white shirt reflects more infra-red radiation so you’ll stay cooler. White walls, white cars, white seats, white shorts, white houses, etc. all act like mirrors for infra-red (IR) radiation. Which is why you can aim your TV remote at a white wall and still turn on the TV. Simply pretend the wall is a mirror (so you can get the angle right) and bounce the beam off the wall before it gets to your TV. It looks like magic!

Click over to this experiment to learn how to make Liquid Crystals.

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Click here to go to next lesson on Calorimeter.

You can’t get through a science or engineering degree without having performed a calorimetry lab. A calorimetry experiment is made of of inexpensive equipment (it only uses a coffee cup and a thermometer) and the calculations needed to do the experiment are pretty easy, so you can already tell that teachers are going to like them. They are useful in figuring out the specific heat capacity and the heat of fucion or dissolution of an unknown substance (usually a lump of metal). Here’s how to make a coffee cup calorimeter and do the calculations:

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Chemists use a bomb calorimeter to measure the heat flow for reactions that involve gases (since the gases would escape out of the coffee cup) and reactions at high temperatures (which would melt the cup). It works the same way as the coffee cup version, only the reaction is sealed and placed in water, which is then placed in an insulated container. It’s a more elaborate setup as well as analysis because now you take into account the heat flow into the parts of the calorimeter. Heat also does work as it transfers energy.

Click here to go to next lesson on Heat Engines.

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The Drinking Bird is a classic science toy that dips its head up and down into a glass of water. It’s filled with a liquid called methylene chloride, and the head is covered with red felt that gets wet when it drinks. But how does it work? Is it perpetual motion?

Let’s take a look at what’s going on with the bird, why it works, and how we’re going to modify it so it can run on its own without using any water at all!

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The bird needs a temperature difference between the head and tail. Since water needs heat in order to evaporate, the head cools as the water evaporates.  This temperature decrease lowers the pressure inside the head, pushing liquid up the inner tube. With more liquid (weight in the head), the bird tips over. The bird wets its own head to start this cycle again.

The trick to making this work is that when the bird is tipped over, the vapor from the bottom moves up the tube to equalize the pressure in both sides, or he’d stay put with his head in the cup.  Sadly, this isn’t perpetual motion because as soon as you take away the water, the cycle stops. It also stops if you enclose the bird in a jar so water can longer evaporate after awhile. Do you think this bird can work in a rainstorm? In Antarctica?

What’s so special about the liquid? Methylene chloride is made of carbon, hydrogen, and chlorine atoms. It’s barely liquid at room temperature, having a boiling point of 103.5° F, so it evaporates quite easily. It does have a high vapor pressure (6.7 psi), meaning that the molecules on the liquid surface leave (evaporate) and raise the pressure until the amount of molecules evaporating is equal to the amount being shoved back in the liquid (condensed) by its own pressure. (For comparison, water’s vapor pressure is only 0.4 psi).

Note that the vapor pressure will change with temperature changes. The vapor pressure goes up when the temperature goes up. Since the wet head is cooler than the tail, the vapor pressure at the top is less than at the bottom, which pushes the liquid up the tube.

It really does matter whether the bird is operating in Arizona or the Amazon.  The bird will dip more times per minute in a desert than a rain forest!

Let’s find out how to modify the bird so it’s entirely solar-powered… meaning that you don’t have to remember to keep the cup filled with water.  Here’s what you need:

• drinking bird
• silver or white spray paint
• black spray paint
• razor
• mug of hot water
• sunlight or incandescent light

Download Student Worksheet & Exercises

In this modification, you completely eliminated the water and converted the bird to solar, using the heat of the sun to power the bird. Now your bird bobs as long as you have sunlight!

How does that work? Since the bottom of the bird is now black, and black absorbs more energy and heats up the tail of the bird. Since the tail section is warmer, the pressure goes up and the liquid gets pushed up the tube. By covering the head with white (or silver) paint, you are reflecting most of the energy so it remains cool. Remember that white surfaces act like mirrors to IR light (which is what heat energy is).

Questions to Ask: Does it work better with hot or cold water? Does it work in an enclosed space, such as an inverted aquarium? On a rainy day or dry? In the fridge or heating pad?

Exercises Answer the questions below:

1. Where does most of the energy on earth come from?
   1. Underground
   2. The sun
   3. The oceans
2. What is one way that we use energy from the sun?
3. What is the process by which the liquid is being heated inside the bird?
   1. Precipitation
   2. Pressure
   3. Evaporation
   4. Transpiration

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Click here to go to next lesson on Hero Engine.

There are lots of different kids of heat engines, from stirling engines to big jet turbines to the engine in your car. They all use clever ways to convert a temperature difference into motion.

Remember that the molecules in steam move around a lot faster than in an ice cube. So when we stick hot steam in a container, we can blow off the lid (used with pistons in a steam engine). or we can put a fan blade in hot steam, and since the molecules move around a lot, they start bouncing off the blade and cause it to rotate (as in a turbine). Or we can seal up hot steam in a container and punch a tiny hole out one end (to get a rocket).

One of the first heat engines was dreamed up by Hero of Alexandria called the aeolipile. The steam is enclosed in a vessel and allowed to jet out two (or more) pipes. Although we’re not sure if his invention ever made it off the drawing board, we do know how to make one for pure educational (and entertainment) purposes.  Are you ready to have fun?

THIS EXPERIMENT USES FIRE AND STEAM…GET ADULT HELP BEFORE YOU OPERATE THE ENGINE.

Here’s what you do:

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Materials:

• soda can
• fishing line
• razor
• stand
• drill or large nail and hammer
• adult help
• candle

IMPORTANT NOTE: As the water boils, your can will spin. The hot steam shoots out the sides, so take care not to get burned. As the can spins, it may wobble and shake, especially if it’s off-center.  Be careful not to get shot with boiling water!!

What’s going on? When the water boils, the molecules inside are turning into hot steam and moving very quickly, bouncing off the can and out the pipes. Rockets and balloons use this same principle – the pressurized air shoots out the open end and the balloon (or rocket)  moves in the opposite direct.  Newton’s third law in motion! The two jets at an angle work together to spin the can.

1. Do you think the size of the hole matters?
2. Does it matter how many candles you use?
3. What if you used four holes instead of two? Six? Twenty?
4. Are beer cans better?

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Click here to go to next lesson on Stirling Engine