Question

Why is mercury used in thermometers?

Answer 1

Mercury used in thermometers b/s it is substance which is very sensitive towards the temperature.So even if there is small change in temperature of body it is easily measured by thermometers.It is also used b/s it doesn't  sticks with the wall of container.

Answer 2

Because it has highest coefficient of expansion. Hence,the slightest change in temperature is notable when used in thermometer.
Hope it helps you. . .