Thermal expansion

Thermal expansion means that when something gets warmer, it gets bigger. When you pour hot water into a cup, the cup will get bigger because the water gets bigger due to the heat. The same thing can happen with other things too. For example, bridges will expand when it's hot outside, and buildings can get bigger when it's too hot. When things like these get too big and there isn't enough room for them, they can break or cause damage.