I also got to learn how a pop pop boat works. The boat uses heat generated from a candle to heat a small aluminum box (boiler), which is connected to 2 straws. When heat is applied to the boiler, water in the boiler evaporates into steam. The expanding steam pushes some of the water in the exhaust tube, propelling the boat forward. The steam bubble then condenses, creating a vacuum which draws water back in through the exhaust tube. The cooled water that is brought back into the boiler is then heated and evaporates into steam, and the cycle repeats. From this project, I learnt that water pressure allows the boat to move forward.