Seventh Grade Energy

Kinetic energy is an expression of the fact that a moving object can do work on anything it hits; it describes the amount of work the object could do as a result of its motion.Whether something is zooming, racing, spinning, rotating, speeding, flying, or diving… if it’s moving, it has kinetic energy. How much energy it has depends on two important things:  how fast it’s going and how much it weighs.  A bowling ball cruising at 100 mph has a lot more kinetic energy than a cotton ball moving at the same speed.

Temperature is a measure of how much kinetic energy the particles in a substance has. 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.

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. We're going to learn about temperature, heat energy, atoms, matter, phase changes, and more in our unit on Thermodynamics.

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. Confused yet? Great! Then let's get started...

Here are the scientific concepts:

• Kinetic energy is energy of motion. The faster something is moving and/or the more massive it is the more kinetic energy it has. KE=1/2 mv²
• Potential Energy is the amount of energy something can use to do work.
• Gravitational potential energy is the amount of energy something has due to its height above the ground. The higher it is and more mass it has the more gravitational potential energy it has. PE=mgh
• Energy can be transferred, in other words it can be changed from one form to another and from one object to another.
• Conservation of energy means that in a closed system energy can neither be created or destroyed.
• Energy efficiency is how much energy in a system is transferred to useless energy. The most common forms of useless energy are sound energy and heat energy.
• The amount of energy transfer needed to change temperature of matter depends on the size and properties of the substance.
• When two objects interact, each exerts a force on the other than can cause energy to be transferred.
• Energy is the ability to do work. Work is moving something against a force over a distance. Mathematically, work = force x distance. Work can be measured in Joules or calories. Power measures how quickly work can be done.
• Mathematically, power is work divided by time. Power can be measured in horsepower or Watts.
• Temperature is a measure of average kinetic energy of matter particles.
• The terms hot, cold, warm etc. describe what physicists call thermal energy. Thermal energy is how much the molecules are moving inside an object. The faster molecules move, the more thermal energy that object has.
• Temperature is basically a speedometer for molecules. The faster they are wiggling and jiggling, the higher the temperature and the higher the thermal energy that object has.
• Heat is the movement of thermal energy from one object to another.
• Heat can only flow from an object of a higher temperature to an object of a lower temperature.
• Heat can be transferred from one object to another through conduction, convection and radiation.
• Heat is movement of thermal energy from one object to another.
• When an object absorbs heat it does not necessarily change temperature.
• Heat capacity is how much heat an object can absorb before its temperature increases.
• Specific heat is how much heat energy a mass of a material must absorb before it increases 1°C. Each material has its own specific heat. The higher a material’s specific heat is, the more heat it must absorb before its temperature increases.

By the end of the labs in this unit, students will be able to:

• Build a working steam boat that uses thermal energy to move through water.
• Design and build a real working external combustion Stirling engine from soda cans.
• Learn how a Hero engine works and why it's not very popular today.
• Build your own thermostat by using heat expansion properties of bi-metallic strips.
• Construct and interpret data that relate kinetic energy to the speed and mass of an object.
• Design and build an experiment that shows what happens when the arrangement of object interacting at a distances changes, and different amounts of potential energy are stored in the system.
• Show how thermal energy is transferred in an experiment while measuring mass, particle kinetic energy (temperature), and other thermal properties and how they relate to each other.
• Differentiate observation from inference (interpretation) and know scientists’ explanations come partly from what they observe and partly from how they interpret their observations.
• Measure and estimate the weight, length and volume of objects.
• Formulate and justify predictions based on cause-and-effect relationships.
• Conduct multiple trials to test a prediction and draw conclusions about the relationships between predictions and results.
• Construct and interpret graphs from measurements.
• Follow a set of written instructions for a scientific investigation.