* The molecules are closer together. In a solid, the molecules are packed tightly together in a fixed arrangement. This is why solids have a definite shape and volume.
* The molecules have less kinetic energy. In a solid, the molecules vibrate in place, but they don't have enough energy to move freely like they do in a liquid. This is why solids are generally more rigid than liquids.
* The substance has a higher density. Because the molecules are closer together in a solid, the solid will have a higher density than the liquid form of the same substance.
* The substance has a specific melting point. The transition from a liquid to a solid happens at a specific temperature called the melting point.
* The substance has a crystalline structure. Most solids have a crystalline structure, meaning their molecules are arranged in a repeating, three-dimensional pattern. However, some solids are amorphous, lacking this regular structure.
Let me know if you'd like more details about any of these points!
