Question

How will the density of mercury change when it is heated?

Answer 1

Well, to know that we should look at its phase diagram (though we expect expansion of the liquid).

You didn't specify starting from what temperature pressure, but we assume `"1 atm"`, or `"0.00101325 kbar"`, and `"298.15 K"`, i.e. ordinary conditions.

An ordinary temperature increase (`10-100` `"K"`, let's say) will leave mercury still in the liquid state as it normally is. Liquids in general are very incompressible, so the volume will hardly change... although to be particular, it will slightly increase (the particles move slightly farther apart while maintaining the same mass, though the intermolecular forces hold it together well).

`=> V = m/D`,

where `m` is mass and `D` is density.

One can see then that the slight increase in volume decreases the density slightly.