This document discusses the differences between solids, liquids, and gases at the particle level and provides information about melting. It notes that in solids, particles are fixed in place and can only vibrate, while in liquids particles can move over each other but remain close together. In gases, particles can move anywhere in their container and are far apart. The document then states that melting occurs when a solid is heated and turns into a liquid, with different materials having different melting points, or temperatures at which they melt.