After breaking away, they shoot into the space above the liquid. The fast-moving vapor molecules can hit objects hard and often, causing a lot of pressure against whatever they hit. This pressure can be used to do work such as pushing on the blades of a turbine , or pushing on the base of a piston . The thermal energy has become mechanical energy, allowing the machine to do work. One type of piston drives a steamboat.
Steam pushes the piston one way.
Then that steam is released and new steam enters the other side, pushing the piston in the other direction. The piston pushes a long arm, called a pitman arm , which turns the paddle wheel. The paddle wheel pushes against the water, moving the boat forward. The steam in the system is cooled, heated again, and reused. Steam engines were the first engines.