Heat and Sound The Laws of Thermodynamics 1 Work Work is done on an object when it changes shape or moves. Work is done by an object when it changes the shape of some other object or moves it. Heat Heat is energy that flows from higher temperature objects to lower temperature objects. Temperature Temperature is a measure of the internal energy of an object. Internal Energy Internal energy is the kinetic energy of the molecules inside an object. (Temperature is a measure of internal energy.)

Heat and Sound The Laws of Thermodynamics 2 The First Law of Thermodynamics “Heat is work, and work is heat.” If work is done on a system (and it does not move), then the system will either increase internal energy or lose heat or both. If we try to crush something, it will increase its temperature or lose heat to the surroundings or both.

Heat and Sound The Laws of Thermodynamics 3 The Second Law of Thermodynamics “Heat cannot of itself pass from one body to a hotter body.”” Entropy (a measure of disorder in a system) in the universe cannot decrease. Systems will not go from disorder to order without increasing the disorder elsewhere. The measure of order in most objects is given by how ordered the molecules are.

Heat and Sound The Laws of Thermodynamics 4 Heat lost by an ideal gas is proportional to its mass and change in temperature. Work done on an ideal gas is given by. The internal energy of the system is then given by the First Law or Thermodynamics First Law Calculations

Heat and Sound The Laws of Thermodynamics 5 The efficiency of a process is given by the following equation. where is the heat added to the system. In the most efficient process, the internal energy is not changed and all of the work goes to heat. Second Law Calculations

Heat and Sound The Laws of Thermodynamics 6 First Law Examples (Double-click on the pictures to see the full websites)

Heat and Sound The Laws of Thermodynamics 7 Second Law Examples