The temperature is defined as the indicator that shows the amount of thermal energy stored in the body, as well as the extent of the movement of its atoms and molecules, as there is a mathematical relationship between the kinetic energy of these molecules and the body temperature, and temperature has many units of measurement that are used to determine how hot The body or its coldness, and temperature is one of the most important factors that determine the direction in which heat is transmitted between different bodies.

Temperature units

There are dozens of measurement units that are used to express temperatures, but there are three of them that are spread globally, and the following is an explanation of the three units used:


It is the unit of measurement adopted in the international system, and bears the symbol (K), so named in honor of its British physicist (Lord Kelvin), and the kelvin scale is commonly used to clarify the relationship of the volume of a gas with its absolute temperature, and the relationship of pressure and volume of a gas with the kelvin temperature. The temperature is one Kelvin, the volume of the gas increases by (1/273) of its original volume, and the same applies to its pressure.

The Kelvin unit is not commonly used in daily life, but it is of great importance in various scientific fields, as it is used in various scientific measurements, such as measuring the degree of activity of the particles of matter, as its movement stops at zero degrees Kelvin, and it is widely used in astronomy.

absolute zero

The term absolute zero is the lowest temperature that exists in nature, and from a scientific point of view, absolute zero cannot be reached, but there is an approach to it, while theoretically it can be said that when absolute zero is reached, the volume of the body is equal to zero, because the size relationship with Temperature is direct, and if substances reach this temperature, their properties and behavior will be similar, and there will be no difference between them.

Celsius System

One of the most famous units of measurement used globally, and it is usually symbolized by the symbol (C), and it was called in the old days the name of the centigrade, but its name changed in the year one thousand nine hundred and forty-eight, in relation to the astronomer (Anders Celsius), who was the first to suggest that the degree of Zero is the freezing point of water, and 100 is its boiling point.

The Celsius unit is used on a daily basis in many countries of the world, and it is widely used in some scientific fields, in addition to the fields of weather forecasts after the media used the centigrade unit in weather bulletins.


It was named by this name after its first founder, the German physicist (Daniel Gabriel Fahrenheit), in the year one thousand seven hundred and twenty-four, and is symbolized by the symbol (F), and the United States of America is one of the countries in the world that uses this unit of measurement the most.

Temperature conversion

Conversion from Kelvin to Celsius (and back)

There is a fixed relationship between these two units. Once a fixed number is added to the percentage, the kelvin is obtained, and when the same number of kelvin is subtracted, the percentage is obtained, and this number is two hundred and seventy-three, and it can be explained mathematically as follows:

  • Kelvin degree = Celsius + 273.
  • Celsius = degree Kelvin – 273.

Converting from Fahrenheit to Celsius (and back)

  • Celsius = (Fahrenheit -32 degrees)/1.8.
  • Fahrenheit = (°C x 1.8) +32.

Temperature conversion law