1. Encircle T if the statement is true and BOX F if otherwise. T F 1. Heat engines do not necessarily need fuel. T F 2. In the real world, engines have never reached the theoretical limit. T F 3. A steam engine is a type of heat engine that uses steam to do work. T F 4. All of the thermal energy that flows through a heat engine can be used to do work. T F 5. According to the first law of thermodynamics, energy must be conserved in the engine. T F 6. In a steam engine, the thermal energy in the exhaust is energy that was used to do work. T F 7. As the steam expands in a steam engine, it pushes a piston outward, doing positive work on the piston. T F 8. In a steam engine, hot steam supplied by a boiler expands within the engine and does work on a piston. T F 9. As a system decreases in entropy, the amount of work it can do on the surroundings or other systems decreases. T F 10. A thermodynamic heat engine, or simply a heat engine, is an engine that uses thermal energy to do mechanical work