Introduce the activity. You can say, “We are going to make a toy car that gets its energy to move from a balloon.
“How do you think we can use a balloon to make a car move?” Talk with your child about how the balloon could make the car move. Talk about what might happen if they blow up the balloon and attach it to the car.
Spend some time talking about energy. “When you blow up a balloon, the air inside stretches the rubber of the balloon. The air and the stretched rubber become potential energy. Potential energy is the energy stored in an object. A balloon without air has no potential energy. A blown-up balloon has potential energy. Potential energy is probably going to turn into a form of energy like kinetic energy. Kinetic energy is the energy of motion or movement.”
“Potential (stored) energy and kinetic (moving) energy make mechanical energy. We can use mechanical energy to power the car we build. What happens when you blow up a balloon and let go of it? Try it!” Discuss how the balloon moves and what happens to the air inside the balloon. You can say, “The potential energy of air and stretched rubber turns into kinetic energy when you let go of the balloon and that makes it zip across the room.
“Let’s build a toy car and watch how the potential energy in the balloon turns into kinetic energy and moves the car to make mechanical energy.”