Final answer:
Blacktop on a driveway is an exception to the rule of thermal contraction when a material cools down.
Step-by-step explanation:
When a material cools, it usually undergoes thermal contraction, which means that its particles move more slowly and become more tightly packed. However, there is an exception to this rule for blacktop on a driveway. Blacktop is a type of pavement that absorbs energy from the sun and heats up quickly. As a result, it expands rather than contracting when it cools down.