# Boyle’s law and Charles’ law

## Boyle’s law:

The relation between the volume and the pressure of a gas at a constant temperature. It was first proposed by the British Scientist Robert Boyle in 1660 AD and the relation is called Boyle’s Law.

Statement: At constant temperature, the volume of a fixed mass of gas is inversely proportional to its pressure.

Mathematically, if V is the volume of a gas of certain mass and p is its pressure, then according to Boyle’s law,

V ∝ 1/p, when the temperature remains constant

or, V = k/p

or, pV = k = constant

The value of k depends on the mass and the temperature of the gas. Hence, the product of the pressure and the volume of a fixed mass of gas at a fixed temperature remains constant.

## Charles’ law:

The relationship between the volume and temperature of a fixed mass of gas at constant pressure was investigated experimentally by the French Scientist Charles in 1787. He concluded that at constant pressure a fixed volume of all gases would expand by the same amount for an equal rise in temperature.

Gay Lussac arrived at almost the same result in 1802. He found that the coefficient of volume expansion of all gases has the same value if pressure is kept constant. In 1842, Regnault showed that the experimental value of this coefficient is 1/273 per degree celsius. Charles’ law is enunciated by combining the experimental results of Gay Lussac and Regnault.

Statement: When the pressure is kept constant, the volume of a fixed mass of gas increases or decreases by (1/273)th part of its volume at 0°C, for each degree of celsius rise or fall in temperature.