Here's why:

* Henry's Law: This law states that the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas above the liquid.

* Higher Pressure = More Dissolved Gas: As the pressure of the gas above the liquid increases, the solubility of the gas in the liquid also increases.

Think of it like this: Imagine you have a bottle of soda. When you open the bottle, the pressure inside decreases. This causes the dissolved carbon dioxide to come out of solution, forming bubbles. The opposite is true when the bottle is sealed – higher pressure means more carbon dioxide can be dissolved in the liquid.