• Heat always flows from a system of higher temperature to a system at lower temperature. . The mass of a system is not altered when it is heated or cooled.
• Heat gained by the cold system is equal to heat lost by the hot system.
(ii) • When a body is heated or cooled,the length of the body changes due to change in its temperature.
• Then the expansion is said to be on linear or longitudinal expansion.
• The ratio of increase in length of the body per degree rise in temperature to its unit length is called as the coefficient of linear expansion.
• It is different for different materials. Its SI unit is `K^(-1)`
• The equation is `(DeltaL)/(L_(0))=alpha_(L)DeltaT`
`DeltaL`- Change in length (Final length - Original length)
`L_(0)` - Original length (Final temperature - Initial temperature)
`alpha_(L)` -Coefficient of linear expansion
