Heat (Thermal) Energy and Heat Transfer
Heat (thermal) energy is due to the movement of atoms and molecules in a substance. The faster the atoms/molecules move the higher the temperature of the substance. Therefore heat energy is really the kinetic energy of the atoms and molecules of a substance.
Heat energy can be used to do work. When a liquid is heated the liquid will eventually boil and change to a gas. The gas takes up more space (volume) then the liquid and can exert a great force. This can be used to drive turbines that can generate electricity.
Heat is the transfer or flow of energy from a hot object to a cold object. It is important to understand that heat only travels from a hot object to a colder object. Thus an object gets warm by receiving heat energy and cold by loosing heat energy.
Heat energy can be transferred in three ways: