Question

explain why the metal lid on a glass jar can be unscrewed easily if the jar is inverted for a few seconds with the lid in very hot water​

Answer 1

Answer:

If we assume it is your average glass pickle-jar with a metal top than heating up the jar will loosen the lid because the metal conducts more heat than the glass. ... As the lid loosens the normal force the glass produces to push back on the lid is decreased so the Frictional force is lowered