How exactly do we measure temperature?

Today’s Video of the Day comes from the American Chemical Society’s Reactions series and features a look at how temperature is measured.

When it comes to human health, it is imperative that we are able to accurately measure our body temperature, as the difference between one or two degrees could mean a nap or a trip to the Emergency Room. But what thermometers actually measure is heat. Temperature reflects the average energy of the molecules in a system, while heat reflects the transfer of energy between two systems that are of different temperatures.

When a thermometer is in a cool place, it loses heat to its surroundings, causing the molecules in its liquid to slow down and contract. This, in turn, pulls down the corresponding numeric value on the scale. But in a hot environment, the thermometer gains heat, causing the liquid to expand and move up up the scale.

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By Rory Arnold, Earth.com Staff Writer

Source: American Chemical Society