The Second Law of Thermodynamics

1. The Second Law of Thermodynamics The entropy of an isolated system remains constant or increases Entropy - A measure of the disorder in a physical system This law states that all processes within an isolated system occur in such a manner that increases the randomness of the system. Examples - spray air freshener, drop food coloring in a glass of water

2. Consequences of the Second Law of Thermodynamics • Heat will never flow spontaneously from a cold body to a hot body. • You cannot construct an engine that does nothing but convert heat to useful work. • Every isolated system becomes more disordered over time.

3. Heat Engines A heat engine uses energy provided in the form of heat to do work and then exhausts the heat which cannot be used to do work. Heat engines such as automobile engines operate in a cyclic manner, adding energy in the form of heat in one part of the cycle and using that energy to do useful work in another part of the cycle.

4. Terms • Adiabatic – no heat added or removed • Isothermal – no change in temperature • Isochoric – no change in volume • Isobaric – no change in pressure Q = 0 U = 0 W = 0

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