Celsius degree

Clinical thermometer graduated from Celsius degrees

The degree Celsius (symbol °C) replaces, since 1948, the degrees Celsius in the International System of Units. Consequently, the degree Celsius (together with the kelvin) has become the current thermometric unit, whose 0 is located 0.01 degrees below the triple point of water and whose heat intensity is equivalent to that of the kelvin.

The degree Celsius belongs to the International System of Units, as an accessory unit, unlike the kelvin, which is the basic unit of temperature in said system.

By international agreement, between 1954 and 2019 the unit degree Celsius and the Celsius scale were defined by absolute zero and the triple point of water. As of 2007, it was clarified that this definition referred to the Vienna Standardized Mean Ocean Water (VSMOW), a precisely defined water standard. This definition also accurately related the Celsius scale to the scale of the Kelvin, the base SI unit of thermodynamic temperature with the symbol K. Absolute zero, the lowest possible temperature, is defined as exactly 0 K and −273.15 °C. Until May 19, 2019, the temperature of the triple point of water was defined as exactly 273.16 K (0.01 °C).

History

Anders Celsius defined his scale in 1742 considering the boiling and freezing temperatures of water, originally assigning them the values 0 °C and 100 °C, respectively (so that a higher value meant a lower temperature); later Jean-Pierre Christin (1743) and Carlos Linnaeus (1745) inverted both points. The proposed method, like the one used in 1724 for the Fahrenheit degree and the Rømer Degree of 1701, had the advantage of being based on the physical properties of materials. William Thomson (later Lord Kelvin) defined in 1848 the absolute temperature scale of it in terms of degrees Celsius. At present the degree Celsius is defined from the kelvin as follows:

t( C)=T(K)− − 273,15{displaystyle t(^{circ}{text{C}})=T({text{K}}})-273{,}15}

The temperature intervals expressed in °C and in Kelvin have the same value.

The Celsius scale is widely used to express the temperatures of daily use, from the air temperature to that of an endless number of domestic devices (ovens, fryers, hot water, refrigeration, etc.). It is also used in scientific and technological work, although in many cases the use of the Kelvin scale is required.

Unit conversion

The melting and boiling temperatures of distilled water at one atmosphere of pressure, on the Kelvin, Celsius, Fahrenheit, and Réaumur scales, are as follows:

The triple point of water is at 273.16 K, that is, 0.01 °C.

The magnitude of a degree Celsius is equivalent to the magnitude of a Kelvin; In other words, a temperature difference has the same numerical value expressed in degrees Celsius as in Kelvin:

Δ Δ t(°C)=Δ Δ T(K){displaystyle Delta t({text{°C}})=Delta T({text{K}}}),!}

You can convert from Celsius to kelvins as follows:

t(K)=t(°C)+273,15{displaystyle t(K)=t({text{°C}})+273,15,!}

And vice versa to go from kelvins to Celsius

t(°C)=t(K)− − 273,15{displaystyle t({text{°C}})=t(K)-273,15,!}

The conversion from degrees Celsius to degrees Fahrenheit is obtained by multiplying the temperature in Celsius by 1.8 and adding 32:

t(°F)=1.8× × t(°C)+32{displaystyle t({text{°F}})=1.8times t({text{°C}}})+32,!}

To convert Fahrenheit to Celsius:

t(°C)=t(°F)− − 321.8{displaystyle t({text{°C}})={frac {t({text{°F}}})-32}{1.8}}{,!}

The Celsius scale is a temperature scale that assigns the value zero (0 °C) to water in the process of melting, and the value one hundred (100 °C) to water in the process of boiling.

From Fahrenheit scale to Kelvin scale:

K=59(°F− − 32)+273,15{displaystyle {text{K}}={frac {5}{9}}}({text{°F}}}-32)+273,15,!}

From Kelvin scale to Fahrenheit scale:

°F=95(K− − 273,15)+32{displaystyle {text{°F}}={frac {9}{5}}{text{K}}}-273,15)+32,!}

Symbol and name

The symbol for Celsius is a small flying circle (not the letter o) followed by the letter C, which form an indivisible block. The Royal Spanish Academy admits writing only the flown circle, without the C, but this notation is not in accordance with international standards, in which the circle is reserved for the degree of plane angle. The name is degree Celsius and, although the General Conference on Weights and Measures rejected the term degree Celsius in 1948 (since this name is reserved for the angle measurement scale), the latter is still in common use. centídegreedegree, i.e. based on a scale giving 100 degrees between the melting and boiling temperature of water, should not be confused with centidegree, which is one hundredth of a degree.

As with most unit symbols, there should be a hard space between the value and °C. Thus, we have that 25 °C (with a hard space) is correct, 25 °C (with two spaces) is incorrect, and 25°C (without a space) is also incorrect.

In Unicode there is the character "℃" (U+2103) that represents the degree Celsius, but it is recommended not to use it.