Freeze only applies if the solidification is directly related to temperature, and is only normally used if the substance is a liquid or gas at normal, everyday, comfortable temperatures, and becomes solid at temperatures we would normally consider cold. Solidify is appropriate if the change is not temperature related, or if it occurs at temperatures we would normally consider hot.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.