Thermal expansion
Most solids lengthen when heated by an amount change in L = alpha x L x change in T.
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Analogy
Railway tracks are laid with small gaps for hot days.
Example
alpha = 12e-6 per Kchange in L = 12e-6 x 10 x 30change in L = 0.0036 m
In practice
A 10 m steel beam warms by 30 K and grows by 3.6 mm.
Questions people ask
Why do bridges have expansion joints?
Materials get longer when the temperature rises. A 100 m steel bridge expands by 3.6 cm for a 30 K rise. Without gaps, the force would buckle the road. Expansion joints give space so the deck can lengthen and shrink without damage.
Why does water behave unusually near freezing?
Most liquids shrink as they cool, but water is densest at about 4 degrees Celsius and then expands as it approaches freezing. That is why ice floats and lakes freeze from the top down. Fish can survive under the ice because the bottom stays near 4 degrees.