Mercury and alcohol, as the main components of thermometers, are called temperature measuring media. Temperature measurement medium can be used to measure temperature because it has the characteristics of thermal expansion and cold contraction.
When the temperature rises, the volume of mercury and alcohol expands obviously. What you see in the thermometer is the height rise of alcohol column or mercury column. In this way, as long as the appropriate scale is marked, people can read out the corresponding temperature.
Alcohol and mercury have different characteristics. Alcohol has a strong cold resistance, while Mercury will solidify at -39 ℃and lose its fluidity. In the cold north, the temperature in winter is about - 40 ℃, so it is generally suitable to measure the temperature with alcohol thermometer. However, compared with alcohol, heat resistance is an advantage of mercury. The boiling point of mercury is 356.72 ℃, and when alcohol reaches 78.3 ℃, it will boil and vaporize rapidly. Mercury thermometers are obviously more suitable for measuring high temperature than alcohol thermometers.
The selection of thermometer depends on the application, so the selection of temperature timing depends on the situation.