Question

Why do we use mercury as a thermometric fluid?

Answer 1

Mercury is used as a thermometric fluid because of it's characteristics, they are as follows:

1. Generally metals expand on heating, Mercury is the only liquid metal that can expand or contract evenly.
2. Mercury is a liquid that can flow but does not stick to the glass.
3. It has a high coefficient of expansion so even a slight change in temperature is notable and sufficient expansion can be detected in the capillary tube of the calibrated part of the thermometer.
4. Mercury has a lower freezing point $(-39°C)$ and a high boiling point $(356.7°C)$ which makes it very suitable to measure higher temperatures.
5. It is opaque and available in a pure state.
6. It is a shiny liquid metal, hence can be easily seen through the glass of the thermometer tube.