It is relatively easy to compress a gas but extremely difficult to compress a liquid or a solid. What reason does the source give for this difference?

1. The difference in compressibility comes down to how tightly packed the particles already are. 2. In gases, atoms and molecules are separated by large empty spaces, leaving lots of room to compress. 3. In liquids and solids, those particles are already packed close together, so compressing them further means fighting strong electromagnetic forces between the particles themselves. 4. It is the liquid and solid state, not the gas state, that involves those strong resisting forces, and both states clearly are made of atoms. _Source: OpenStax College Physics (CC BY 4.0), Ch 5 "Further Applications of Newton's Laws: Friction, Drag, and Elasticity", section 5.3 Elasticity: Stress and Strain_