What factors determine if a rock melts?

Answer 1

Melting is a state change caused by the break of the strong bonds forming the solid that are substituted by weaker bonds characteristic of a liquid.

Transmitting heat to a solid body causes the temperature to increase, that is the energy of random thermal motion of the molecules constituting the body increases (in fact it is proportional to the temperature itself).

When a certain critical temperature arrives, the thermal energy is sufficiently high to break now and then the bonds among molecules. Further heat is not used to increase temperature, but to remove solid bonds. As a matter of fact, after reaching the melting temperature further heat does not increase temperature, but increases the quantity of liquid with respect to the quantity of solid. Weaker and more elastic liquid bonds are spontaneously formed at such temperature between available molecules that have been freed from the solid state.

In case of rocks they are generally composed by a mix of different solids that melt at different temperatures, thus it is possible that a part of rock melts at a certain temperature, while another part remains solid and increases further its temperature.

Answer 2

The main factors that determine if a rock melts are temperature, pressure, and rock composition. A rock will melt when its temperature exceeds its melting point, which varies depending on the type of rock. Pressure can also affect the melting point of a rock, with higher pressures typically requiring higher temperatures to melt. Additionally, the composition of the rock, including the presence of minerals with different melting points, can influence its melting behavior.