An object doesn't change size very much with temperature, but the change can be quite inexorable when we are dealing with solids or liquids. Very large forces can arise if thermal expansion effects occur. Some examples:

• A glass jar will break if you fill it half-full of very hot water. The top and bottom of the jar want to be different sizes.
• Concrete roads and sidewalks are built in sections, with space left between the panels. Otherwise, they would crack on very cold days and heave and buckle on very hot days.
• The traditional way to fasten an iron rim to a wooden wheel (or put an iron hoop around a wooden barrel) was to heat the rim red hot. This made it slightly larger, so that the wheel could be forced into the rim; after the rim cooled and shrank, it was firmly held in place. The modern version of this is that one should not mix bolts and nuts made of different metals -- there will be a temperature range in which the bolt is larger than the nut (and the nut is then frozen in place), and another range where the nut is bigger than the bolt (and then it is not held in place securely).
• A modern application of thermal expansion is in the design of the power plants for nuclear submarines. Instead of trying to control the power level by pushing in and pulling out control rods, the reactor is designed so that when it is too hot it expands (which decreases the rate of reaction), and and when it is cool is contracts (which increases the rate of power production). Thermal expansion eliminates the need for an operator that never gets distracted or a complicated electrical circuit.
• If the ocean becomes 1 degree (^oF) warmer, its volume will increase by 0.01%. Since the ocean is several miles deep, this implies that the surface will rise about a foot, giving a change in the sea level. In the process, the beach line moves landwards 20 feet. People owning beach houses (or even living close to the ocean) find this alarming.