Systems • A set of interconnected parts. • Open system- one that exchanges both matter and energy with its surroundings • Example? • Closed system- one that cannot exchange matter but can exchange energy with its surroundings • Example? • Isolated system- on that cannot exchange matter or energy with its surroundings
Heat and Work • What is the difference between heat and work? • Work- involves movement of matter from one location to another • Heat- is a transfer of thermal energy from one location to another • Both heat and work can affect systems • Increase it • Heat can be added to a system from its surroundings or work can be done on a system by its surroundings • Decrease it • Heat can flow out of a system into its surroundings or work can be done by the system on its surroundings
Law of Conservation of Energy • What is it? • Energy cannot be created or destroyed. It can only be transformed from one form to another. The total amount of energy never changes.
First Law of Thermodynamics • The total energy, including heat, in a system and its surroundings remains constant. • When ever heat is added to a system, it transforms into an equal amount of some other form of energy • Heat added to the system= mechanical energy + heat
In reality though the mechanical energy gained never comes close to the theoretical maximum because most of the input energy is lost from the system as heat.
The Perfect Machine • Hypothetical machine in which all the input energy is converted completely into mechanical energy • In order for a machine to be classified as a perfect system or a perpetual motion machine, all the mechanical energy must be completely conserved. • It is impossible to create a truly perfect machine.
The Second Law of Thermodynamics • Heat always flows naturally from a hot object to a cold object, but never naturally from a cold object to a hot object. • When heat in a heat engine flows from high to low, this heat can be converted into mechanical energy. However only some of the input heat can be converted into mechanical energy, the rest is expelled as exhaust heat. • In order to have heat move from cold to hot, you have to have work.
Heat Engine • Read page 204
Heat Pump • Read page 205
Heat Engine vs Heat Pump • What is the difference between the two? • What are the similarities?
To Do • Answer questions 1-10 on page 205 in your notes