Answer:
Running hot water over the metal lid of a jar causes the metal to expand. This is due to the principle of thermal expansion, which states that most materials expand when heated and contract when cooled.
Step-by-step explanation:
The heat from the water causes the molecules in the metal lid to move faster and spread apart, resulting in an increase in the size of the lid. This slight expansion can be enough to break the seal or make the lid slightly larger than the jar, making it easier to twist and open.