Heating the water on the paper towel increases the motion of the water molecules. When the molecules have enough energy, they can move fast enough to break away from the attractions holding them to ...

When water molecules do this, they change from liquid water to water vapor – a gas. This changing from a liquid to a gas is called evaporation. Heating a liquid causes the water molecules to move ...

The bird is a simple heat engine. The tail is at room temperature and is the heat source while the wel head is cooling due to evaporation on its surface and is the heat sink. As the gas in the tail ...