Thermal Energy
Thermal Energy is the heat stored inside an object because of how fast its tiny parts are moving.
A flat box holds dozens of small balls resting nearly still on its floor. When you warm the box, every ball starts to bounce and shake faster. The more you heat the box, the faster every ball moves. All that bouncing is stored heat — the hotter the box, the more of it there is inside.
Explaining thermal energy by grade level
Set a black bottle and a white bottle in the sun. The black one gets much hotter. The dark color soaks up more warmth from the light. That extra warmth inside the bottle is heat stored up from the sun.
Projects that explore thermal energy
A solar furnace bounces light from many mirrors onto a single point, and each additional mirror sends more heat to that spot. The more mirrors you aim at the target, the faster the tiny particles in the material there move. A large array of 256 mirrors or more can raise the temperature high enough to melt steel.
When a black bottle absorbs the sun's energy, the air inside warms and the tiny particles in it speed up. Those faster-moving particles push outward with more force, and within minutes the balloon on the black bottle begins to inflate. The white bottle's balloon stays flat because the white surface reflects most of the sun's energy away.
A parabolic curve lined with aluminum foil reflects light toward a single point called the focal point. All that concentrated sunlight speeds up the tiny particles at that spot, building up heat quickly. The sun's energy focused there makes the particles move fast enough to cook a hot dog placed on a skewer at that point.
On a sunny day, a solar panel heats up quickly — the tiny particles inside the cell move faster, and that extra motion can lower the electrical output. You set up three identical solar cells at noon, each with a different heat condition: one on a metal plate, one on a raised plywood platform, one with a fan beneath it. The fan-cooled cell produces the most power because blowing air removes heat and slows those particles back down.