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
(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.