Why is Mercury used in Thermometers?

By BYJU'S Exam Prep

Updated on: November 9th, 2023

Mercury is used in thermometers because it expands uniformly, has a high boiling point, and is available in a liquid state at room temperature. A thermometer consists of a long glass tube with a bulb that contains a thermometric liquid to measure the body temperature. Mercury is the thermometric liquid or chemical used in thermometers. It has a high coefficient of expansion, which means it expands uniformly when the temperature changes.

Reason Mercury used in Thermometers

A mercury-filled reservoir is located at one end of a sealed glass tube calibrated in degrees Celsius and/or degrees Fahrenheit. As the temperature rises, the mercury in the reservoir expands, moving up the thermometer, and as the temperature drops, it contracts and sinks. Mercury has a low specific heat capacity and is a good conductor of heat.

All these reasons make it ideal for detecting high temperatures. Lastly, it is opaque and shiny, making it visible in the glass tube of the thermometer.

  • Worldwide deposits of mercury, primarily as cinnabar, are found (mercuric sulfide).
  • Grinding either synthetic mercuric sulphide or natural cinnabar yields the red color vermilion.
  • The chemical element mercury has the atomic number 80 and the symbol Hg.
  • Formerly called hydrargyrum from the Greek words Hydor (water) and Argyros, it is also known as quicksilver (silver).
  • Mercury is the only metallic element known to be liquid at standard circumstances for temperature and pressure. It is a hefty, silvery d-block element.


Why is Mercury used in Thermometers?

The high expansion coefficient of Mercury makes it ideal for use in thermometers, which means it expands uniformly when heated. It has a high boiling point and a low freezing point which makes it ideal for detecting high temperatures. Mercury looks shiny and opaque, which makes it visible in the glass tube.

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