A piece of solid wax is placed in pan and heated on a stove. After a while, the solid wax becomes a liquid. Why does the wax become a liquid?
In a solid state, all the particles are closely compact, however they do vibrate, but they do keep a fixed shape. They do not have enough energy to break the intermolecular forces of attraction (bonds) existing between the particles. Hence, they vibrate on the spot and retain a solid state.
When heated on the stove, the wax particles gather heat energy from the heat of the stove. Therefore, the wax particles have enough energy to break apart the intermolecular forces of attraction (bonds) resulting in the free moving wax particles also known as the liquid state.