Beakman explains that steam has a lot of power behind it and that a man named Hero in Ancient Greece figured out how to use it to make a ball spin. However, it wasn't until the invention of the steam engine that people knew how to use steam. Beakman uses a model to explain how the steam moves the piston back and forth to turn a wheel, which is how steam engine trains work.
Mr. Wizard demonstrates the difference between steam and water vapor to Billy using a teapot and flames. He explains that steam is the gas form of water and that we mistakenly refer to water vapor as steam in everyday conversation.