Mercury is an intriguing element. It is the only metal that is liquid at room temperature and has one of the highest densities – higher than that of solid iron even! However, the densest element at room temperature is Osmium. Barring few exceptions, solid states of most matter have higher densities than their liquid states. 

So, a child asked an excellent deductive question, one that even I had never wondered about – Mercury is already very dense in its liquid state. If we freeze it to change it into a solid, its density would most likely increase further. Is the density of frozen, solid Mercury then higher than or comparable to that of Osmium, which is the densest solid element ever?

I had to research to find the answer to this one! The answer is no. The density of liquid Mercury (13.53gm/cc) increases by only 3.5% upon freezing, which is still less than that of Osmium (22.57g/cc). 

When we allow the children to think freely, its amazing how far they can go and what connections they make!