Why is mercury used in making of thermometers?

A clinical thermometer is used to measure our body temperature.
The commonly used clinical thermometer is made up of a narrow tube called capillary tube of thick glass and at the end of the capillary tube there is a glass filled bulb with mercury.
Mercury is a liquid metal at room temperature.
As glass is a poor conductor of heat the wall of the bulb is kept thin so that the transfer of heat between Mercury and its surroundings can take place easily. .
As Mercury is a good conductor of heat it rises up and the kink prevents the Mercury from going down

Mercury is used in thermometers because

  1. It does not stick to the glass tube.
  2. It expands on providing heat to it.
  3. It has lower freezing point and higher boiling point.
  4. It is a shining metal and when it expands, the expansion can be easily seen.

And because of this reason we use mercury in thermometers instead of  any other substance because these properties are not possible.


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