Why do you use hot water to remove a tight metal cap easily?

Answer 1

Often, lids are made of metals which are great conductors of electromagnetic waves (including heat). When warm water is applied to a "difficult" lid, excitement of the atoms in the metal occurs (very slight) which causes a slight expansion. This expansion helps the lid to be moved from it's grip on the jar or bottle. This is also found in plastics. Although not through expansions. The heat from the warm water literally softens the plastic.

Answer 2

The metal of the jar lid heats up, and the molecules that make up the jar lid vibrate. These vibrations increase and therefore cause the metal of the lid to expand. The metal in the lid expands more than the glass of the jar. Therefore the lid is slightly larger than when it is cool, making it easier to twist open.

Answer 3

As heating begins, the contents of each jar expand, and a change in internal pressure occurs. At first, gases are vented from the jar. When finished, the pressure outside the jar is greater than inside. This difference pulls the lid down onto the jar and forms a vacuum seal.

Answer 4

The heat makes the metal on the lid expand so it is easier to remove from the jar. Hope this helped.

Answer 5

because hot water have heat and heat helps to open any tight metal thing easily

Answer 6

Heat causes objects to expand, and the metal lid should expand slightly more than the glass jar.

Answer 7

The lid is usually made of metal. Heating the metal causes it to expand making it easier to twist the lid off the glass jar.