Menu

Thermodynamics.
Transformation of energy

Thermal energy and combustion.
Effects of thermodynamics

Entropy

Celsius Degrees

Celsius degrees

The degree Celsius (in symbol in ° C), is the unit of a temperature measurement scale, named after the Swedish astronomer Anders Celsius (1701 - 1744), who first proposed it in 1742. The Celsius scale is a scale to indicate the temperature at which the  temperature ranges are degrees Celsius.

The Celsius scale sets the melting point of ice in a mixture of water saturated with air at 0 ° C and the boiling point at 99.974 ° C under standard pressure conditions (1 bar, slightly less than an atmosphere, pressure at water boils at 100 degrees Celsius).

Originally conceived by the Celsius scale it had the boiling point of water at 0 ° C, and the freezing point of 100 ° C. After his death, however, the scale was reversed in 1745 by Linnaeus, transforming it into the one now commonly used.

The current official definition of the Celsius scale places 0.01 ° C as the triple point of water and a degree as 1 / 273.16 of the temperature difference between the triple point of water and absolute zero. This definition of degrees Celsius ensures that the temperature difference of one degree Celsius represents the same temperature difference of one kelvin.

Conversion of degrees Celsius to other temperature units

Formulas to convert degrees Celsius to other temperature units.

  • Conversion of degrees Celsius to degrees Fahrenheit à ° F = (9/5 × ° C) + 32
  • Conversion from degrees Fahrenheit to degrees Celsius à ° C = (5/9) × (° F - 32)
  • Conversion of degrees Celsius to kelvin à K = ° C + 273.15
  • Conversion from Kelvin to degrees Celsius at ° C = K - 273.15

Anders Celsius originally proposed that the freezing point of water be 100 ° C and the boiling point 0 ° C. The ladder was reversed in 1745 at the suggestion of Linnaeus, or perhaps by Daniel Ekström, the producer of most the thermometers used by Celsius.

The Celsius and Fahrenheit thermometric scales intersect at the same value of -40 degrees, that is, the value of -40 ° C corresponds to that of -40 ° F.

One way to convert Celsius to Fahrenheit is to multiply by 1.8 and then add 32.

° F = ° C × 1.8 + 32

Conversely, to convert Fahrenheit to degrees Celsius, subtract 32 and divide by 1.8.

° C = (° F - 32) / 1.8

The Celsius scale is used in most parts of the world on a daily basis, although in the mass media it is still called centigrade until the 1990s, especially in weather forecasts. In the United States (as well as in the unincorporated territories and freely associated states of the Pacific), in Belize, Liberia and some Caribbean islands the Fahrenheit scale is used, but also these countries use the Celsius or Kelvin scale in the Applications scientific or technological.

Other temperature scales are: Newton (circa 1700), Rømer (1701), Fahrenheit (1724), Réaumur (1731), Delisle or de Lisle (1738), Rankine (1859), Kelvin (1862) and Leyden (circa 1894) . Note that "kelvin" is lowercase because it is an SI unit, even if it is derived from the noble title by scientist William Thomson.

What is the difference between degrees Celsius and degrees Celsius?

Since there are a hundred divisions between these two reference points, the original term for this system was degree centigrade or centesimal degree. In 1948, the ninth Conférence générale des poids et mesures (CR 64) officially changed the name to Celsius to remove a number of ambiguities:

  • the centi prefix is ​​used by the SI system for submultiples;
  • a more correct name, at least since Linnaeus was invested, would have been "hectograd";
  • the hectogram is also ambiguous and in enology it indicates the alcohol content per hectoliter of wine;
  • the term "degree centigrade" was also used to indicate the hundredth degree used to measure angles;
  • Kelvin is also a degree centigrade, as far as obtained, like Celsius, dividing in equal parts the interval between two fundamental fixed points.

The decision of the Conférence générale des poids et mesures was aimed at removing ambiguities and unequivocally associating the creation of the scale with Celsius (despite the important contribution of Linnaeus); in addition, the scale was uniformed to those of Kelvin (raised by Lord Kelvin), Fahrenheit, Réaumur and Rankine, all with the name of their inventor.

Despite this, there are often people who refer to degrees centigrade as "degrees Celsius", in the same way that they use the concept  centigrade scale.

Why is the Celsius scale not considered an absolute scale?

The existence of an absolute temperature scale is a consequence of the second principle of thermodynamics.

According to the second law, the absolute temperature scale starts from the existence of absolute 0º. This condition is only fulfilled by two basic units:

  • Kelvin degree
  • Rankine grade.

Zero degrees Kelvin correspond to -273.16 degrees Celsius.

Author:

Published: October 25, 2018
Last review: April 17, 2020