Question

why do solids change into liquid on heating

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Answer 1

This can be explained concerned with the heat energy, when a solid changes to liquid. This is called melting. The particles in a solid are held tightly and packed close together to strong forces of attraction acting between them and still they are vibrating. ... The energy isprovided when solid is heated up.

Answer 2

the kinetic energy in solids is very less on heating the kinetic energy of the molecules of solids increases which leads to formation of a liquid it is because the kinetic energy of a liquid is more than that of solid and the kinetic energy of a gas is more than that of a liquid and solid both