Why do bubbles in boiling water get larger....?

Question

Why do bubbles in boiling water get larger as they rise to the surface?

Answer 1

As the liquid changes to gas, it becomes lighter than the surrounding mass-so it rises.  As the bubbles rise they are surrounded with less and less constricting (less dense) mass which allows the expansion to ever increasing size until it is finally released.  The size of the bubble is in proportion to its surroundings. Energy is never lost - just transformed.

Answer 2

As the bubbles rise, the surrounding water turns to vaper and is collecting with the bubble.