## Comparing Coefficients of Thermal Expansion for Gases, Solids and Liquids

The coefficients of thermal expansion, linear and volume, for solids and liquids for some substance are given in the following table.

 Substance Linear, Volume, Aluminium Steel and Iron Glass (Pyrex) Glass (jar) Brick and concrete Rubber Ethanol Methanol Petrol Air

Notice from the table that the coefficients of volume expansion are all almost exactly three times the coefficients are linear expansion. This is a consequence of length being measured in m but volumes being measured in m^3 :

If a length increases by 1% , thenbutso that the volume has increased by 3% or three times the percentage increase in volume.

Notice also that the coefficients for solids are smaller than those for liquids, which are smaller than those for gases. This is a consequence of the forces between atoms and molecules in solids are stronger than the forces between atoms and molecules in liquids, and the forces between atoms and molecules in gases are very weak indeed.