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# Conversion of Temperature

## Definition

Temperature is the measure to describe the degree of hotness or coldness of an object. Celsius scale, Fahrenheit scales and Kelvin scale are three different scales used to measure the temperature of an object. From Physics to Geology to mathematics, temperature is an important concept in all fields. like any other physical quantity, the temperature is defined as the measure of the warmth or the coldness of a substance or object with reference to some standard value. Let us know about the instrument that is used to measure the temperature of a body or a region.

## What instrument do we use to measure temperature?

The instrument used for measuring temperature is called a thermometer. Thermometers are the most common instrument to measure temperature. The liquid thermometer is the simplest form of a thermometer. The liquid thermometer contains a thin glass tube filled with a small amount of mercury. Thermal expansion is the concept that drives the working of these liquid thermometers. A small change in the temperature causes changes in the volume of the liquid.  But, this form of effect is at the maximum when the liquid expands within the thin tube of the thermometer. When mercury gets hotter, it increases in size by an amount that is directly related to the temperature. So if the temperature increases by 30 degrees, the mercury expands and moves up the scale by thrice as much as if the temperature increase is only 10 degrees.

## Units used to Measure Temperature

There are three major scales that are used to define the temperature measured by a thermometer. These scales are –

1. Celsius scale
2. Fahrenheit scale
3. Kelvin scale

Let us learn about them one by one.

## Celsius Scale

Celsius scale is a temperature scale based on 0 o for the freezing point of water and 100 o for the boiling point of water. This scale uses the symbol oC. The Celsius temperature range was originally defined by setting zero as the temperature at which water froze, i.e. zero degrees C was later redefined as the temperature at which ice melts. The Celsius scale is also called the centigrade scale. The Celsius scale was first introduced and is named after by the Swedish Physicist, Engineer, and Astronomer, Anders Celsius. The Celsius scale follows a system of a relative interval or scale instead of an absolute system of ratio or scale. However, the Modern Celsius scale is referred to be based on the triple point of Vienna Standard Mean Ocean Water, and on the concept of absolute zero as well. This implies that neither the boiling point nor the melting point of water describes the modern Celsius scale.

## Fahrenheit Scale

The Fahrenheit scale is a temperature scale that is based on the freezing point of water at 32°F and the boiling point of water at 212°F. The Fahrenheit scale was introduced by and also named after the physicist Daniel Gabriel Fahrenheit in 1720 A.D. This scale uses the symbol ° F. The lowest defining point in the Fahrenheit scale is the temperature of a solution of brine with an equal amount of ice, water, and salt (ammonium chloride). The temperature of the average human body was first established at 96 ° F, which was later adjusted to 98.6 ° F. In this scale, the lower fixed point is considered 32 ° F, and the upper fixed point is considered 212° F. The region between these two temperatures is divided into 180 equal parts so that each part equals to one Fahrenheit degree ( 1° F ). Thus, the freezing point of water is 32 ° F, and the boiling point of water is 212 ° F on the Fahrenheit scale.

## Kelvin Scale

The Kelvin scale is named after the physicist William Thompson, the first Baron Kelvin. In the mid-1800s, he was the first person to correctly figure out just how cold absolute zero was. In this scale, the two fixed temperatures taken are ice-point 0°C and the steam point (100°C) and the interval between these two is divided into 100 equal parts. Each division in the kelvin scale called a kelvin (K) is equal to a degree on the Celsius scale, but the difference is where zero is. In the Celsius scale, 0 o is the freezing point of water while in the Kelvin scale the zero point is at absolute zero. Therefore, 0 o K is equal to -273.15 o C, 0 o C is equal to 273.15 kelvins. The Kelvin scale is used for very low or very high temperatures when water is not involved. The symbol for kelvin is “ K ,” and it does not use the term “degrees.” So if it’s 18 °C outside, it’s also 64 °F and 291 K.

## How to Convert Temperature from Celsius Scale to Fahrenheit Scale

We know that the freezing point of water is 0 degrees on the Celsius scale and 32 degrees on the Fahrenheit scale, whereas the boiling point of water is 100 degrees on a Celsius scale and 212 degrees on the Fahrenheit scale. Let us now learn about the formula to Convert Temperature from Celsius Scale to Fahrenheit Scale. This formula is given by –

O C = $\frac{F -32}{1.8}$ . . . . . . . . . . . . . . . . . . . . . . . . .  . . . ( 1 )

This equation can also be written as

F = ( C x $\frac{9}{5}$  ) + 32 . . . . . . . . . . . . . . . . . . . . . .  . . . ( 2 )

where

C = Measure of temperature in degrees Celsius ( ° C ).

F = Measure of temperature in degree Fahrenheit  (° F )

The above two equations tell us how to convert Celsius into Fahrenheit and vice versa.

Using the equations above, we can now list down the steps that should be used to convert the temperature in Celsius into Fahrenheit Scale. These steps are as below –

1. The first step is to identify the given temperature in Celsius.
2. The next step is to multiply the temperature noted in the first step by 9
3. The product obtained in the above step should be then divided by 5
4. In the last step, we add 32 to the result obtained in the previous step which gives us the temperature in Fahrenheit.

Let us understand it using an example.

Example

Convert 26 o C to Fahrenheit

Solution

We have been given 26 o C and we are required to convert it to Fahrenheit scale.

Going by the steps above, let us first multiply 26 by 9. We will get 26 x  9 = 234

Now, we will divide the result obtained in the previous step by 5. We will get 234 ÷ 5 = 46.8

Next, we will add 32 to the result obtained in the previous step which gives us the temperature in Fahrenheit. We will get 46.8 + 32 = 78.8

Hence, 26 o C after converting into Fahrenheit scale would be 78.8 o F

## Celsius Scale to Fahrenheit Conversion Chart

Using the formula that we have discussed above, we can list down the conversion values of different temperatures from the Celsius scale to the Fahrenheit scale. These conversion values serve as a quick reference guide for converting different temperatures from the Celsius scale to the Fahrenheit scale.

## Difference between the Celsius Scale and the Fahrenheit Scale

Now that we have learnt how to convert the Celsius scale to the Fahrenheit scale, let us list down the core difference between these two scales used for measuring temperature. The following tables show the difference between the Celsius scale and the Fahrenheit scale –

## Challenges Faced while converting temperature from Celsius scale to Fahrenheit scale

Although we have a clear formula that defines the relationship between the Celsius scale and the Fahrenheit scale, still there are times some challenges that are faced by people when converting temperature from the Celsius scale to the Fahrenheit scale. Some of these challenges are –

1. Both, the Celsius scale as and Fahrenheit scales are offset, which means that neither of them is defined as starting at zero. This makes remembering both the scales difficult.
2. For every additional unit of heat energy, the Celsius and Fahrenheit scales add a different additional value. Because of this setup, it’s impossible to say that doubling the °C or °F value doubles the amount of heat energy, so it’s difficult to get an intuitive grasp of how much energy 1 degree Fahrenheit or Celsius actually is.

## Conversion of Celsius Scale to Kelvin Scale

The Kelvin scale is based on these experiments. It is not arbitrary, but it is designed so its zero point is absolute zero. It is also important to note in the case of the Kelvin scale there is no use of degree. This gives us a direct relationship between the Celsius scale and the Kelvin scale. Thus the relation between the Celsius scale, Kelvin scale and the Fahrenheit scale is given by –

0 K = -273.15 o C = – 459.67 o F

Using the above formula we can define a conversion chart that lists down all the three temperature scales.

Let us understand it using an example.

Example

Convert 20 degrees Celsius to Kelvin

Solution

We have been given 20 o C and we are required to convert it to Kelvin Scale.

We know that 0 K = -273.15 o C

Therefore,

Temperature in Kelvin = 20 + 273.15 = 293.15

Hence, 20 o C when converted to the Kelvin scale will be 293.15 K

## Celsius Scale to Kelvin Scale Conversion Chart

Below we have a chart that lists down the conversion values from Celsius scale to Kelvin scale –

## Key Facts and Summary

1. Temperature is the measure to describe the degree of hotness or coldness of an object.
2. The instrument used for measuring temperature is called a thermometer. Celsius scale is a temperature scale based on 0 o for the freezing point of water and 100 o for the boiling point of water.
3. The Celsius scale is also called the centigrade scale.
4. The Fahrenheit scale is a temperature scale that is based on the freezing point of water at 32°F and the boiling point of water at 212°F.
5. O C = $\frac{F -32}{1.8}$
6. F = ( C x $\frac{9}{5}$  ) + 32
7. The freezing point of water or the melting point of ice in the Celsius scale is 0 ° C. It is the lower fixed point of the scale. The boiling point of water, as described in the Celsius scale, is 100 ° C. It is the upper fixed point of the scale.
8. The freezing point of water or the melting point of ice in the Fahrenheit scale is 32 ° F. It is the lower fixed point of the scale. On the Fahrenheit scale, the boiling point of water is 212 ° F. It is the upper fixed point of the scale.
9. 0 K = -273.15 o C = – 459.67 o F
10. For every additional unit of heat energy, the Celsius and Fahrenheit scales add a different additional value. Because of this setup, it’s impossible to say that doubling the °C or °F value doubles the amount of heat energy, so it’s difficult to get an intuitive grasp of how much energy 1 degree Fahrenheit or Celsius actually is.
11. The Kelvin scale is based on these experiments. It is not arbitrary, but it is designed so its zero point is absolute zero. It is also important to note in the case of the Kelvin scale there is no use of degree.