| Equilibrium | When the concentration of the product and reactant are the same. This usually happens when the rate of the forward reaction is the same as the rate of the backwards reaction, resulting in a net change of zero. |
| Evaporation | When molecules at the surface of a liquid turn into gas. |
| Boiling | When molecules throughout the entirety of the liquid are turning into gas. This occurs at temperatures and pressures beyond the boiling point. Usually a visible vapor is present. |
| Le Chatelier's Principle | When something disrupts the equilibrium, then the reaction will shift to a new equilibrium to accommodate this change. |