Definitions

# Temperature Scales

Temperature scales have the function of measuring the temperature (degree of agitation of molecules) of a body. From this measurement, it is possible to determine whether the body is hot or cold.

Throughout history different scales have been developed, currently only three are used: Celsius, Fahrenheit and Kelvin. The standard used by the three scales are the melting and boiling points of water. Keep reading to understand better.

## Know the 3 types of temperature scales

Below you can learn more about the 3 types of temperature scales with the relevant details of each one.

### Celsius scale

The Celsius scale was developed by Swedish astronomer Anders Celsius in 1742 under the name Centigrade. This first nomenclature refers to the fact that this is a centigrade thermometric scale, that is, it has one hundred intervals between the melting and boiling points.

In 1948, the scale was renamed Celsius, in honor of its creator, and as a way to avoid confusion with the acronym SI (International System), Chinese . In addition, it was used to designate all measurement units. The reference used by Celsius for his thermometric scale were the following values ​​of melting and boiling points of water :

100°C – Melting point of water

0°C – Boiling point of water

However, the values ​​attributed to melting and boiling points underwent a reorganization made by thermometer creators such as the Swedes Daniel Ekström and Carolus Linnaeus, becoming as follows:

0°C – Melting point of water

100°C – Boiling point of water

The values ​​are still used today. The Celsius scale is used in virtually all countries.

### Fahrenheit scale

The Fahrenheit scale was created in 1724 by physicist and engineer Gabriel Fahrenheit. The idea arose when the engineer learned about the construction of mercury thermometers. Fahrenheit adopted as a reference in its scale the values ​​of the melting and boiling points of water, which are as follows:

32°C – Melting point of water

212°C – Boiling point of water

The Fahrenheit scale has 180 intervals between 32 and 212, so it is not a centigrade scale like Celsius. This scale was widely used in British colonies. Even today, this scale is used in countries like England and the United States.

### Kelvin scale

In 1864, Irish physicist and engineer William Thomson, also known as Lord Kelvin , proposed the Kelvin scale. For Thomson, it was necessary that there was a thermometric scale capable of assigning the total absence of particle movement to a material, which he named as absolute zero.

Lord Kelvin determined that his scale could not have negative values ​​for temperature. Like Celsius and Fahrenheit, he used the melting and boiling points of water as a reference:

273 K – Melting point of water

373 K – Boiling point of water

The Kelvin scale is the thermometric scale adopted by the International System.

## How to convert one thermometric scale to another

The three thermometric scales we present are used in different parts of the world. Therefore, it is important to know how to convert one scale to the other. This can be done very simply, see below:

As the three thermometric scales are used in different places, it is interesting to know how to convert one into the other. To do so, just use the following relation:

Tc = Tf-32 = Tk-273

__ _____ _____

5 9       5

In this formula we have:

1. Tc – Temperature in degrees Celsius
2. Tf – Temperature in degrees Fahrenheit
3. Tk – Kelvin Temperature

From this formula we can learn the form of:

Tk = Tc + 273

Tc = Tk – 273

Tc = Tf-32

__ _____

5 9

Tf-32 = Tk-273

_____ ______

9 5

## Conversion examples

For a clearer understanding of how to convert from one scale to another, check out the following examples:

### Converting 150 K to Celsius

The conversion of 150 K (Kelvin) to degrees Celsius can be done according to the following expression:

Tc = Tk – 273

Then, we have:

Tc = 150 – 273

Tc = – 123°C

### Converting 75°F to Celsius

To convert 75°F (Fahrenheit) to Celsius, use the following expression:

Tc = Tf-32

__ ____

5 9

Then, we have:

Tc = 75-32

__ ______

5 9

9.Tc = 5.43

9Tc = 215

Tc = 215

____

9

Tc = 23.88°C