Question

why do solids change into liquids on heating?

Answer 1

A solid changes to liquid on heating! When we heat a solid then the heat energy changes to kinetic energy of particles of solid! They start vibrating on a faster rate! Due to heat enegy the secondary bonds between the particles break down. After that the particles start seperating away due to which the fluidity increases and the. The state of the material start changing! So on heating the solid changes to liquid!

Answer 2

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