Melting phenomenon refers to the process that an object changes from solid to liquid. In this process, the object will absorb external heat. When ice and snow melt, they are solid and melt into liquid. During the melting process, ice and snow will continuously absorb external heat, but the temperature will remain unchanged. It takes 2~3 minutes for water to become a liquid completely before the temperature rises.
Solids are divided into crystal and amorphous according to their melting characteristics, and crystals have a fixed melting point (the temperature is constant when melting); Amorphous: There is no fixed melting point (the temperature rises continuously when melting).
Generally speaking, the melting point of the same crystal is related to atmospheric pressure. The greater the pressure, the higher the melting point; The lower the pressure, the lower the melting point. Except water, the higher the pressure, the lower the melting point; The lower the pressure, the higher the melting point. Therefore, water has a unit system phase diagram different from other pure substances, and its solid-liquid line slope is negative, which is very different from other substances.
State change: In physics, the process of changing a substance from one state to another is called state change. They can be transformed into each other, so there are six state changes: melting, solidification, vaporization, liquefaction, sublimation and sublimation.
Other states of matter, such as plasma state, supersolid state, neutron state, Bose-Einstein condensed state, soft matter, etc.