If you apply more and more heat to a solid, the particles vibrate faster and faster. Eventually the particles will have enough energy to break free of the forces holding them in line ....

When that happens, the solid turns to a liquid! The particles are still held by forces that keep them grouped together, but now they are free to vibrate and move around within the substance. As you apply more heat energy, the particles move around faster.

As a liquid, the substance can hold a lot more heat. The more heat you add, the faster the particles move around. That's why liquids have a higher specific heat capacity than solids.

http://www.worsleyschool.net/science/files/state/changes.html