Expansion and contraction of solids


•    People who design structures such as buildings and bridges are very careful about the materials they use.

•    They choose materials that will not break when temperatures change.

•    A building project often requires two or more materials.

•    Architects should not choose materials that expand and contract in different ways in different seasons.

•    One material might expand faster than another material.

•    If this happens, there could be damage to the structure.

•    A few examples of solids that expand and contract are:

      (i)    Metal lids on jars

      (ii)   Hot-water pipes in homes

      (iii)  Metal frames around windows

      (iv)  Railroads

      (v)   Car engines

•    Engineers use steel rods to make concrete bridges and buildings stronger.


•    The rods help support the concrete.

•    Steel needs to expand and contract in the same way that the concrete does.

•    If the steel does not expand at the same rate as the concrete, the concrete can crack.

•    Eventually the building could fall.