Consider the example of a wooden wheel in which an iron rim ( ring ) has to be fit. The iron ring is made a bit smaller than the wheel. The ring, when heated, expands and gets bigger in size to fit on the wooden wheel. When the ring cools down, it contracts, that means it’s size reduces back to its original size and therefore it gets tightly fixed over the wheel. As there is change only in the physical property of shape, the change can be reversed.