Question

how does the density of Mercury helps in the thermometer?

Answer 1

Most metals are good conductors of heat and they are solids at room temperature. Mercury is the only one in liquid state at room temperature.

Answer 2

Mercury, which is often used inthermometers, has a density of 13.534 g/mL at room temperature.

Mercury is the only one in liquid state at room temperature. It's used in thermometersbecause it has high coefficient of expansion. Hence, the slightest change in temperature is notable when it's used in a thermometer. It also has a high boiling point which makes it very suitable to measure higher temperatures.