State Avogadro's law.

Explanation

(a) When a body is heated or cooled, the length of the body changes due to the change in its temperature. Then the expansion is said to be linear or longitudinal expansion. The ratio of increase in length of the body per degree rise in temperature to its unit lengthh is called as the coefficient of linear expansion.
The value of coefficient of linear expansion is different for different materials. The equation relating the change in length and the change in temperature of a body is
`(DeltaL)/L_(0)=alpha_(L)DeltaT`
`DeltaL-` Change in length
`L_(0)-` Original length
`DeltaT-` Change in temperature
`alpha_(L)-` Coefficient of linear expansion.

(b) Equal volumes of all gases under similar conditions of temperature and pressure contain equal number of molecules.