Question

Which metal is used in a thermometer?
A. Copper
B. Mercury
C. Sodium
D. Silver

Answer 1

Hint: Thermometer is used to measure the temperatures. So the substance used in the thermometer must have a high coefficient of thermal expansion, it should be sensitive to small temperature change. Find out which metal given the option satisfies these conditions. In addition to this metal used in thermometers does not stick to the inner surface of the glass.

Complete step by step solution:
The substance used in thermometer should have following properties:
1. It must have a high coefficient of thermal expansion.
2. It should be sensitive to small temperature change.
3. Substance used must be in liquid form and it should not stick to the surface of glass.
Out of the given options mercury satisfies all these conditions. Mercury is the only metal which exists in liquid form at room temperature. It is a shiny liquid metal with a high coefficient of expansion. The advantage of being shiny is you can easily see the level in the glass thermometer when we check our body temperature. It also has a high boiling point which makes it very suitable for measurement of high temperatures.
Therefore the correct answer is option A.

Note: Mercury has a very strong cohesive force hence its droplet is always spherical in the shape and it does not stick to the surface of glass. A slight change in temperature is notable using mercury thermometers. It has very high surface tension therefore it forms a lower meniscus compared to other liquids. It also has very low vapour pressure. It is also used in manometers to measure the pressure in the pipes. It is used in the Sigma manometer. It also has high specific gravity.