Why does the water bottle containing liquid nitrogen explode?

Answer 1

Liquid Nitrogen in a water bottle will explode because of pressure build up.

Liquid nitrogen vaporizes rather quickly and when it transitions from liquid to gas, the pressure increases if kept at the same volume.

Think of boiling water in a closed container. It is similar to that but liquid nitrogen evaporates at much lower temperature, it will explode at room temperature.

Let's say you submerged this water bottle below the boiling point of liquid nitrogen and put liquid nitrogen in the bottle, the bottle will not explode.

It is a mechanical explosion (simple transfer of forces) not a chemical explosion like with hydrogen where hydrogen gas ignites.

Answer 2

When liquid nitrogen inside a sealed container like a water bottle evaporates, it turns into nitrogen gas and expands rapidly. This sudden increase in pressure can cause the water bottle to explode because it is not built to withstand such high pressures.