Pressure is inversely proportional to melting point. The greater the pressure, the lower the melting point. For example, when traveling in the snow in winter, the snow will melt quickly under the pressure of trampling, and the melting temperature is below MINUS 5 degrees Celsius.

Generally speaking, impurities will lower the melting point of substances. For example, the melting point of an alloy is lower than that of any component.

The melting point of a substance is the temperature at which the solid and liquid of a pure substance reach equilibrium under a certain pressure. That is to say, at this pressure and melting point temperature, the chemical potential of a solid pure substance is equal to that of a liquid, while the surface part of a solid system (nano-system) of a pure substance with great dispersion cannot be ignored, and its chemical potential is not only a function of temperature and pressure, but also related to the particle size of solid particles, which belongs to the first-order phase transition process of thermodynamics.