If the volume of a gas goes up, then the pressure will go down, assuming the temperature remains constant.

This is based on Boyle's Law, which states that the pressure of a gas is inversely proportional to its volume.

Here's a simple way to understand it:

* Imagine a balloon: If you blow more air into the balloon (increasing the volume), the balloon expands. This expansion causes the pressure inside the balloon to decrease.

Let me know if you'd like to explore this further!