Match the following terms, 1. heat engine 2. heat pump 3. boiler 4. thermostat •a machine that converts the internal energy of a fuel into mechanical energy. •an appliance that extracts heat energy from one source and deposits it elsewhere. •an appliance that controls the maintenance temperature of a heating system. •a heating appliance that uses heat energy released from fossil fuels to warm water for use in radiant or convection heating systems.