| Gas | the form of matter that is an easily compressible fluid; a given quantity of gas will fit into a container of any size and shape |
| Standard temperature and pressure (STP) | the reference conditions for gases. chosen by convention to be 00C and 1 atm |
| Absolute temperature scale | a temperature scale in which the lowest temperature that can be attained theoretically is zero |
| Atmosphere (atm) | a unit of pressure equal to exactly 760 mmHg; 1 atm = 101.325 kPa |
| Boyle's law | a law stating that the volume of a sample of gas at a given temperature varies inversely with the applied pressure |
| Charies's law | a law stating that the volume occupied by any sample of gas at a constant pressure is directly proportional to the absolute temperature |
| Density | the mass per unit volume of a substance or solution. |
| Diffusion | the process whereby a gas spreads out through another gas to occupy the space with uniform partial pressure |
| Effusion | the process in which a gas flows through a small hole in a container |
| Ideal gas law | the equation PV = nRT, which combines all of the gas laws |
| Kelvin (K) | the SI base unit of temperature; a unit on an absolute temperature scale |
| Kinetic-molecular theory | the theory that a gas consists of molecules in constant random motion |
| Partial pressure | the pressure exerted by a particular gas in a mixture |
| Pressure | the force exerted per unit area of surface |
| Vapor | the gaseous state of any kind of matter that normally exists as a liquid or solid. |