Gases can be compressed easily because there is a large amount of space between the individual molecules, which are very active and move around at high speed. When gases are compressed, the particles are forced much closer together, allowing a huge amount of particles to fit a small space.
Its a displacement reaction
To relate the quantity of a substance to the amount of heat transferred and heat capacity, temperature, number of moles is given by
q=ncpΔT
where
n is number of moles
cp is molar heat capacity
ΔT=Tfinal−Tinitial is the temperature difference
Chemical properties describe how things undergo chemical reactions, while physical properties describe how things behave when they're not undergoing reactions.
In the case of melting a metal, the melted metal continues to be the same material - just in a liquid rather than a solid form. As a result, melting (and all phase changes, for that matter) is a physical change and the ability of the metal to melt at 450 degrees is a physical property.
