Why are gases compressible while liquids are not, despite both being composed of molecules?

Gases have a lot of empty space between their molecules, so when you squeeze them the molecules can move closer together, making the gas smaller. Liquids, on the other hand, already have their molecules packed very tightly, leaving almost no room for the molecules to move closer. Because the molecules in a liquid are already almost touching, applying pressure can’t make them fit any tighter, so the liquid’s volume stays roughly the same. Think of blowing up a balloon (a gas) that shrinks when you press it, versus squeezing a water bottle (a liquid) that hardly changes size. This difference in how much space is between molecules is why gases are compressible while liquids are not.