Question

Why metal such as mercury and galium become semi liquid ( earlier semi liquid ) at room temprature ?

Answer 1

when you apply heat to a solid, you will make the atoms of that solid vibrate about their equilibrium positions within their crystal structure. If you apply enough energy, you can over come the binding energy of the atoms to each other (the atoms shake themselves loose), and the solid becomes a liquid. The amount of energy required to overcome the atomic binding is the melting point of the solid, and is given by a specific temperature which is characteristic of each different solid material. The larger the atomic binding energy between atoms, the higher the melting point will be.

Gallium and mercury each have a melting point than is less than room temperature due to weakly bonded atoms within the solid structure. Mercury though has a much more complex physics to explain why its melting point is so low, and requires working knowledge of quantum mechanics to explain, which is probably beyond the level at which you are studying.

Answer 2

thanks again Jonny