Hot-bulb engine

A hot-bulb engine is like a really cool toy that uses fire to make things move. The engine has a big metal bulb that gets really hot when you light a fire inside. The bulb is connected to a metal cylinder that has a piston inside that can move up and down. When the bulb gets really hot, it makes the air inside the cylinder expand and push the piston up. Then when the fire goes out and the bulb cools down, the air inside the cylinder gets smaller and it sucks the piston back down. This movement makes the engine turn a wheel or do something useful like pumping water. It's like magic, but it's really just science!