Heat and Cold

Measuring Temperature

What chemicals are used in thermometers?

The two liquids that are typically used in a thermometer are mercury or alcohol. The alcohol in thermometers is dyed red to be easier to read, while mercury has a silver color. Both liquids work well in determining temperature, but alcohol thermometers are safer. Should a mercury thermometer break or leak, the liquid metal inside could evaporate and the fumes are toxic; also, mercury tends to expand or contract more slowly than alcohol. Mercury, furthermore, can’t measure temperatures below –38°F (–38.9°C) because that is the point at which it turns into a solid. The disadvantage of alcohol, however, is that it tends to evaporate or polymerize over time.


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