Réaumur scale facts for kids
The Réaumur scale is a way to measure temperature. It's named after René-Antoine Ferchault de Réaumur, a French physicist who invented it in 1731. The unit for this scale is called Réaumur, often shortened to "Ré" or "r".
On this scale, the melting point of ice is 0 degrees Réaumur. The boiling point of water is 80 degrees Réaumur. These points are measured under normal air pressure. This means there are 80 equal steps, or degrees, between freezing and boiling water.
How Réaumur's Thermometer Worked
Réaumur first used ethanol (a type of alcohol) in his thermometers. Ethanol expands more than mercury when it gets warmer. This made it seem like a good choice for showing small temperature changes.
However, ethanol had some problems. It doesn't expand evenly at all temperatures. Also, ethanol boils at a very low temperature. This meant ethanol thermometers couldn't be used for many things, especially very hot temperatures. Because of this, people who made instruments soon started using other liquids. They still kept the idea of 80 degrees between freezing and boiling water.
Why Mercury Became Popular
In 1772, a scientist named Jean-André Deluc studied different liquids used in thermometers. At that time, new ideas about heat were being developed.
Deluc found that thermometers using mercury worked best. He did an experiment to show this. Imagine you mix two amounts of water, like two liters, that have different temperatures. The final temperature of the mixed water should be exactly in the middle of the two starting temperatures. Deluc found that this only worked reliably when mercury thermometers were used.
Because of this discovery, most thermometers started using mercury from the late 1700s. So, while some thermometers might still have an 80-degree scale, if they don't use ethanol, they are not exactly like Réaumur's original design.
Images for kids
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This thermometer shows both the Réaumur and Celsius scales.
See also
In Spanish: Grado Réaumur para niños
