Ideal gas: A gas that obeys Boyle's law and Charles's law, and hence the Ideal gas equation.
Boyle's law: The pressure, p, of a fixed mass of gas is inversely proportional to its volume, V, at constant temperature (i.e. p ∝ 1/V).
Charles's law: The volume, V, of a fixed mass of gas is proportional to its absolute temperature, T, at constant pressure (i.e. V ∝ T).
It is found experimentally that at constant pressure and temperature the volume of a gas is directly proportional to the amount of gas, n, and at constant volume and temperature the pressure is directly proportional to the amount of gas, n. Here are two graphs which show these facts clearly.
Avogadro's hypothesis: Equal volumes of different gases at the same temperature and pressure contain the same number of molecules (or atoms for monoatomic gases).
Ideal gas equation: pV = nRT. R is called the universal gas constant,
Ideal gas: a gas for which the individual molecules or atoms occupy negligible volume, and for which there are no attractive or repulsive forces between the molecules (or atoms).
Dalton's law of partial pressures: The total pressure of a mixture of gases is the sum of the partial pressures of the individual gases in the mixture. All real gases deviate from ideal behaviour, the deviation increasing with increasing p and decreasing T.
Vapour: An alternative term for gas. It is usually used when it is in contact with the liquid form, solid form or solution of the same substance, or is at a temperature at which it could be made to condense by increasing its pressure. The term evaporation illustrates this.
In each of the following assume that the ideal gas equation is obeyed.