Most solids expand when heated. The reason for this is that this gives atoms
more room to bounce about with the large amount of kinetic energy they have at
high temperatures. Thermal expansion is a relatively small effect which is approximately
linear in the absolute temperature:
One can also talk of a volume expansion coefficient
If the solid is isotropic such as is the case for cubic polycrystalline or amorphous
solids then their is a simple relation between the coefficient of thermal expansion
and the coefficient of volume expansion:
Typical numbers for 
range from 
for hard solids to 
organic liquids. Mostly thermal expansion is a nuisance for engineers and there is
much interest in creating solids with little or no thermal expansion. I am actually
working on understanding a new interesting and promising material in this respect
which has a negative coefficient of thermal expansion that is it contracts with
increasing temperature. Mixing some of such a material with other materials which
expand upon heating it may be possible to create solids with little or no
thermal expansion.