Henry's Law states that the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas above the liquid at a constant temperature.

In simpler terms, this means that:

* Higher pressure = More gas dissolved

* Lower pressure = Less gas dissolved

This is why, for example, opening a bottle of soda causes the dissolved CO2 to fizz out. The pressure inside the bottle is reduced, making the CO2 less soluble in the liquid, and it escapes as bubbles.