Liquids and Glasses

When a crystalline solid melts to a liquid, the regularity of the lattice is lost, but some local order may be retained. For example, in crystalline ice, each O atom is surrounded by four other O atoms linked by hydrogen bonds. In liquid water, the hydrogen bond network is partially retained, at least instantaneously, but long-range order is lost as the individual molecules are free to move about. Liquids with weaker intermolecular interactions are even more chaotic.

If we freeze a pure liquid very slowly, giving the atoms or molecules time to find their places in the lattice, a crystal grows. On the other hand, if we freeze the liquid quickly, the chaos of the liquid may be frozen in. The extreme case where there is no order at all is called a glass, often thought of as a supercooled liquid. Other solids may have regions of crystalline order, but lack long-range order.