 The physical change of a substance from one state (solid, liquid or gas) to another.  Involves potential energy between particles.

 There is potential energy between particles due to their location and therefore form bonds.  If the particles are far enough apart, the bonds can break.  A decrease in potential energy causes an increase in kinetic energy, thus ‘releasing’ energy

 Energy required to melt a substance goes into rearranging the molecules.  Energy required to vaporize a substance mostly goes into separating the molecules.

 Whenever heat is added to a system, it transforms to an equal amount of some other form of energy.  The added energy will: 1) increase the internal energy of the system if it remains in the system. 2) do work if it leaves the system.

 Change in thermal energy = heat added - external work done by the system

ProcessConditions IsovolumetricNo work done and no change in volume IsothermalNo change in temperature and internal energy AdiabaticNo energy transferred as heat Isolated System No heat or work interaction with surroundings

 The process of compression or expansion of a gas so that no heat enters or leaves a system.  Example: Cylinder of a gasoline engine Intake, compression, ignition, power stroke, exhaust

 Heat will never of itself flow from a cold object to a hot object.  Heat can only flow from hot to cold.

Changes internal energy into work done.

 The measure of the amount of disorder.  If disorder increases, entropy increases.  Entropy normally increases in physical systems.  When there is work input, entropy decreases.

 You can’t win (because you can’t get any more energy out of a system than you put in).  You can’t break even (because you can’t even get as much energy out as you put in).  You can’t get out of the game (because entropy in the universe is always increasing).