In sixth grade, many students begin studying preliminary physics concepts; different types of energy are an important component to understanding these. The two most basic energy types are potential and kinetic energy. Potential energy is stored energy that can happen or is waiting to happen but hasn't been activated yet. Kinetic energy is that energy in motion, once it has been released. The difference between these types of energy is easily demonstrated through simple activities. At the sixth-grade level, it is usually best to keep the concepts simple and basic, setting the stage for future investigation of energy.
Potential and Kinetic Energy: Jumping Jacks
Have students assume a standing X position, with arms above their shoulders in a wide V and legs apart in an inverted V. Tell them to hold the position, and explain that they are exemplifying potential energy, just waiting to be converted into kinetic energy -- energy in motion. Allow them to do a jumping jack. Explain that, as they move, they're creating kinetic energy; at each pause, however short, their bodies are holding potential energy.
Potential Energy: Chemical Energy
For an interactive and messy experiment that sixth graders will love, demonstrate the relationship of potential energy and chemical energy using vinegar and baking soda. Explain that vinegar and baking soda are made of molecules that contain potential energy in their chemical bonds. Mix half a cup each of water and vinegar in a plastic flask with a cork; put a teaspoon of baking soda in a coffee filter, insert it in the flask, cork quickly and move away. The energy created -- kinetic energy created when chemical interaction converts potential energy -- will blow the cork right off the flask. For a less messy -- but also less dramatic -- experiment, pour vinegar over a pile of baking soda and watch the energy conversion occur.
Potential Energy and Gravity
A bouncing ball is an interesting way to demonstrate a rapid conversion from potential to kinetic energy and back, created by gravity. Allow students to hold a ball over their heads, let it bounce off the pavement and allow it to continue bouncing. Explain that gravity is the force that converts the ball's potential energy to kinetic energy; when it hits the pavement, it possesses potential energy for an instant, and then the force of the ground converts it to kinetic again as it bounces upward.
Potential and Kinetic Energy: Rubber Band
Rubber bands provide an excellent vehicle for explaining potential energy to sixth-grade students. Give a rubber band to each student. Ask them to hold it tightly and stretch it almost as tightly as possible. Explain that the stretched rubber band exemplifies potential energy, which they can feel in the tension as the rubber band pulls against their hands. Then let them let go of the rubber band -- pointing it at the wall and not at each other. Explain that movement in the rubber band demonstrates potential energy being converted to kinetic energy.