Temperature Scales - Types, Formula and Conversion (2023)

Temperature scales are a fundamental concept that every individual should know. Any object with comparatively more internal energy (energy possessed by its molecules) will have a high temperature, while an object with comparatively less internal energy will have a low temperature. The temperature of a body is measured with a device called a thermometer. There are different scales to measure temperature. For example, a clinical thermometer usually measures temperature in degrees Celsius or degrees Fahrenheit.

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(Video) Converting Between Temperature Scales (Celsius, Fahrenheit, and Kelvin)

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What are temperature scales?

The temperature scale is a parameter used to measure temperature. A thermometer is used to measure the temperature of a body on different scales. Each thermometer has a temperature scale that measures body temperature. There are different units that are used to measure temperature. The most common scale for measuring temperature is the Celsius scale. Express the temperature in degrees Celsius.

Fig.: Temperature scales

What are the different temperature scales??

There are four main scales used to measure temperature. They will be discussed as follows:

1. Kelvin scale:British physicist William Thompson, also known as Lord Kelvin, invented the Kelvin scale. The Kelvin temperature scale is based on the kinetic theory of molecular motion. On the Kelvin scale, absolute zero is the temperature at which no molecular motion occurs. Absolute zero is the coldest possible temperature. The freezing point (ice point) of water on this scale is \({\rm{273}}\,{\mkern 1mu} {\rm{K,}}}\) and the boiling point (point of steam) of water is \({\ rm{373}}\,{\mkern 1mu} {\rm{K,}}\) Between the two points there are \({\rm{100}}}\) equal subdivisions on the Kelvin scale. This scale has no negative values. The Kelvin scale is commonly used in scientific calculations. Kelvin is the SI unit of temperature and is represented by the letter \({\rm{'K'}}{\rm{.}}\).
2. Celsius scale:The Swedish astronomer Celsius invented this scale. On the Celsius scale, the freezing point (ice point) of water is taken as \({\rm{0}}\,^\circ {\mkern 1mu} {\rm{C}},\) and the boiling point (steam point) of water is assumed to be \({\rm{100}}\,^\circ {\mkern 1mu} {\rm{C}}.\) Between the two points are \( {\ rm {100}}\ ) equal divisions on the Celsius scale.
3. Escala Fahrenheit:This scale was introduced by the German physicist Daniel Gabriel Fahrenheit. On this scale, the freezing point of water is taken as \({\rm{32}}\,^\circ {\mkern 1mu} {\rm{F,}}\) and the boiling point of water is take as \({\rm {212}}\,^\circ {\mkern 1mu} {\rm{F}}{\rm{.}}\) Between the two points there are \({\rm{180 } }\ ) equal subdivisions on the Fahrenheit scale.
4. Escala de Reaumur:The Reaumur scale was invented by Rene-Antoine Ferchault de Reaumur. The freezing point of water on this scale is marked zero, and the boiling point of water is taken as \({\rm{80}}\,^\circ {\rm{Re}}\) between the two points, there are \(80\)equal subdivisions on the Reaumur scale.

Commonly used temperature scales

The most commonly used temperature scales are the Celsius scale and the Fahrenheit scale. There are two types of thermometers, namely laboratory thermometers and medical thermometers. The temperature of the human body is measured with a clinical thermometer, which displays the temperature in degrees Celsius \(\left( {^\circ {\rm{C}}} \right)\) and degrees Fahrenheit \(\left( { ^\ circ {\rm{F}}} \right)\) The measurement range of a clinical thermometer extends from \(35\,^\circ {\mkern 1mu} {\rm{C}}\) to \(42\ , ^\circ {\mkern 1mu} {\rm{C}}\) The normal temperature of the human body is \({\rm{37}}\,^\circ {\mkern 1mu} {\ rm{C}} \ ) to \( {\rm{98}}.{\rm{6}}\,^\circ {\mkern 1mu} {\rm{C}}\) To measure temperature in laboratories , a laboratory thermometer is used. It goes from \({\rm{ – 10}}\,^\circ {\rm{C}}\) to \({\rm{110}}\,^\circ {\mkern 1mu} {\rm { C}}\)

A thermometer uses mercury as a heat sensitive material that rises when it comes in contact with a body. The division of the thermometric scale at which the mercury rises gives the body temperature reading. Some thermometers use alcohol (ethanol) to measure extremely low temperatures.

Relationship between different temperature scales - formula

The freezing or ice point of water is taken as the lower set point when establishing a temperature scale for the thermometer, and the boiling point of water is taken as the upper set point of the temperature scale.

The following formula gives the relationship between the Kelvin scale, the Celsius scale, and the Fahrenheit scale:

\(\frac{{C\, – \,LFP}}{{UFP\, – \,LFP}}\, = \,\frac{{K\, – \,LFP}}{{UFP\, – \,LFP}}\, = \,\frac{{F\, – \,LFP}}{{UFP\, – \,LFP}}\)

Where \(LFP\, = \) Lower fixed point on a given scale

\(UFP\, = \) Upper fixed point on a given scale

\(C\, = \) Temperature on the Celsius scale

\(F\, = \) Temperature on the Fahrenheit scale

\(K\, = \) Temperature on the Kelvin scale

\(\frac{{C{\mkern 1mu} – {\mkern 1mu} 0}}{{100{\mkern 1mu} – {\mkern 1mu} 0}}{\mkern 1mu} = {\mkern 1mu} \ frac{{K{\mkern 1mu} – {\mkern 1mu} 273}}{{373 – 273}} ​​= \frac{{F{\mkern 1mu} – {\mkern 1mu} 32}}{{212 {\ mkern 1mu} – {\mkern 1mu} 32}}\)

\(\right arrow \,\frac{C}{{100}} = \frac{{K – 273}}{{100}} = \frac{{F – 32}}{{180}}\)

1. Relationship between the Celsius scale and the Kelvin scale:From the above formula we obtain the relationship between the three temperature scales. The relationship between the Celsius scale and the Kelvin scale is given by \(C\, = \,K\, - \,273\).
2. Relationship between the Fahrenheit scale and the Kelvin scale:The relationship between the Fahrenheit scale and the Kelvin scale is given by \(F = \,\frac{9}{5}(K\, - \,273)\, + \,32\).
3. Relationship between Celsius and Fahrenheit scale:The relationship between the Celsius and Fahrenheit scales is given by \(F\, = \left( {\frac{9}{5}\, \times C} \right)\, + 32\). Note that the lower set point is the same on all temperature scales and the upper set point is the same on all temperature scales.

Conversion of temperature scales - examples

P.1. Convert\({\rm{0}}\,^\circ {\mkern 1mu} {\rm{C}}\) hasta \(^\circ {\rm{F}}\)
Sol:Given the temperature on the Celsius scale \({\rm{ = }}\,{\mkern 1mu} 0{\,^{\rm{o}}}{\rm{C}}\)
The formula to convert degrees Celsius to degrees Fahrenheit is given by \(F\, = \,\left( {\frac{9}{5} \times C} \right) + 32\)
Substituting the given temperature value, we get:
\(F\, = \,\left( {\frac{9}{5} \times 0} \right) + 32\)
\(\Right arrow F = 32{\mkern 1mu}\,^\circ {\rm{F}}\)

F.2. convert\({\rm{45}}\,{{\mkern 1mu} ^{\rm{o}}}{\rm{F}}\) hasta \(^{\rm{o}}{\rm{ C}}\)
Sol:Given is the temperature on the Fahrenheit scale \(= 45\,{{\mkern 1mu} ^{\rm{o}}}{\rm{C}}}\)
The formula to convert degrees Fahrenheit to degrees Celsius is \(C\, = \,\frac{5}{9}(F\, - \,32)\)
Substituting the given temperature value, we get:
\(C\,\, = \,\frac{5}{9}(45\, – \,32)\)
\(\Rightarrow C = \frac{5}{9} \times 13 = 7,222\,{{\mkern 1mu} ^{\rm{o}}}{\rm{C}}\)

F.3. Convert \(250\,{\rm{K}}\,{\rm{bis}}\,^\circ {\rm{C}}.\)
Sol: Given is the temperature on the Kelvin scale \(= 250\,{\rm{K}}\)
The formula to convert Kelvin to degrees Celsius is given by
\(C\, = \,K\, – \,273\)
Substituting the specified temperature value into the above formula, we get:
\(C{\mkern 1mu} {\mkern 1mu} = {\mkern 1mu} 250{\mkern 1mu} – {\mkern 1mu} 273{\mkern 1mu} = {\mkern 1mu} \, – 23\,^ \circ {\rm{C}}\)

F.4. Convert\(120\,^\circ {\rm{F}}\,{\rm{a}}\,^\circ {\rm{C}}\)
Sol:Given the temperature on the Fahrenheit scale \(= 120\,^\circ {\rm{F}}\)
The formula for converting degrees Fahrenheit to degrees Celsius is given by
\(C\, = \,\frac{5}{9}(F\, – \,32)\)
Substituting the given temperature value, we get:
\(C\, = \,\frac{5}{9}(120\, – \,32)\)
\(\Rightarrow C{\mkern 1mu} = \,\frac{5}{9} \times 88{\mkern 1mu} = {\mkern 1mu} 48,889\,^\circ {\rm{C}}\)

From this article we can conclude that different temperature scales are used to measure the degree of heat or cold of a substance. The most widely used temperature scale is the Celsius scale. It measures the temperature of a body in units of degrees Celsius or degrees Centigrade. Using different temperature scales based on a person's convenience helps them measure extremely high or low temperatures.

Frequently asked questions about temperature scales

Frequently asked questions about temperature scales are listed below:

F.3. Why are there three different temperature scales?
Answer:The different temperature scales make it easy to measure extremely high or low temperatures and measure the exact temperature value. For example, we get a repeated number if we convert \(120{\mkern 1mu} \,^\circ {\rm{F}}\) to degrees Celsius. Therefore, we cannot get an exact value on the Celsius scale.

F.4. What is absolute zero on a Kelvin scale?
Answer:Absolute zero or \(0\,{\rm{K}}\) is the temperature at which the kinetic energy of the molecules is zero. There is no molecular motion at absolute zero. Absolute zero is the lowest possible temperature.

q5What are the five temperature scales?
Answer:The five temperature scales are as follows:
A. Kelvin-Skala
B. Celsius scale
C. escala Fahrenheit
D. Reaumur-Skala
It is. Rankine scale

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