Simplify the following text for a Grade 6 native English-speaking person.
Original: Since the heat pump or refrigerator uses a certain amount of work to move the refrigerant , the amount of energy deposited on the hot side is greater than taken from the cold side . One common type of heat pump works by exploiting the physical properties of an evaporating and condensing fluid known as a refrigerant .
Simplified: A heat pump forces the refrigerant to change from a gas to a liquid .