What is the Relationship Between Celsius and Kelvin Scale of Temperature?

Although you may be familiar with the notion of temperature, many people confuse it with heat. Temperature is a measure of how hot or cold one thing is in comparison to another (its thermal energy content), whereas heat is the movement of thermal energy between objects of various temperatures. 

Temperature is typically measured using three distinct scales: Fahrenheit (expressed as °F), Celsius (°C), and Kelvin (K). Thermometers use materials that expand or contract when heated or cooled to detect temperature. For example, mercury or alcohol thermometers include a reservoir of liquid that expands when heated and contracts when cooled, causing the liquid column to lengthen or shorter as the temperature of the liquid varies.

Celsius scale

The Celsius scale is a temperature scale introduced by Anders Celsius in 1972. When it is first introduced 100⁰ is used to represent the freezing point of water and 0⁰ to represent the boiling point of the water. These values are changed as 0⁰ to represent melting point and 100⁰ to represent the boiling point of water. Celsius scale is also known as the Centigrade scale. This scale has 100 equal divisions each representing 1⁰ C. The lowest temperature that is possible on the Celsius scale is -273 ⁰C obtained by converting Absolute zero of temperature into Celsius.

• Units: ⁰C
• The freezing point of water: 0 ⁰C
• The boiling point of water: 100 ⁰C
• Absolute zero: -273 ⁰C

Kelvin scale

The Kelvin scale is a temperature scale introduced by Lord Kelvin in 1848 based on thermodynamic principles whose properties don’t depend on any substance. The freezing point in the Kelvin scale is at absolute zero. This scale has freezing point at 273 K and a boiling point of 373 K. Kelvin scale is also known as the SI scale of temperature.

• Units: K
• The freezing point of water: 273 K 
• The boiling point of water: 373 K
• Absolute zero: 0 K

Can Negative Kelvin temperature possible?

The lowest temperature that a substance can have is absolute zero. At this temperature, the particles inside the substance cannot be moved and complete motion between particles is ceased. Since absolute zero in Kelvin scale is 0 K and the substance cannot be cooled further so, negative Kelvin temperature is not possible, but there are few experiments in which scientists have produced gas with negative Kelvin temperature.

What is Absolute Temperature?

The temperature at which compound atoms and molecules have less energy than that particular temperature is called Absolute Temperature. It’s a point beyond which the substance cannot be cooled and the motion of gas particles is zero. It can also be called Thermodynamic temperature. This temperature corresponds to the absolute zero of a temperature scale.

Advantages of using Kelvin scale over Celsius scale

• Celsius scale temperature change doesn’t give an idea about the volume or kinetic energy of substances because their absolute temperature is not 0.
• Whereas the Kelvin scale gives a clear idea regarding the volume and kinetic energy of gases since its absolute temperature is 0 K.
• Kelvin scale is thermodynamic whereas the Celsius scale on other hand is not.
• Kelvin’s scale is linear with absolute zero.
• All the ideal gas laws which involve temperature take Kelvin scale temperature since the Celsius scale is not linearly dependent with absolute zero and may give false results.

Relationship between Celsius Scale and Kelvin Scale of temperature

Celsius Scale and Kelvin Scale both are used to measure the temperature and the same unit divisions are made in both scales. The difference is Celsius Scale starts at 0 whereas Kelvin Scale starts at 273. Since the same number of divisions are made if one unit of temperature increased on the Celsius scale then the same happens with the Kelvin scale.  The temperature in the Kelvin scale is equal to the sum of temperature in the Celsius scale and starting point of the Kelvin scale (273K).

• Conversion of Celsius scale temperature to Kelvin scale temperature: Kelvin Scale temperature (K) = 273 + Celsius Scale temperature ( ⁰C)
• Conversion of Kelvin scale temperature to Celsius scale temperature: Celsius Scale temperature (⁰C) = Kelvin Scale temperature (K) – 273

Sample Problems

Problem 1. The Boiling point of a substance ‘X’ is 100 ⁰C. What is the boiling point value of ‘X’ in Kelvin (K)?

Solution:

Given,

Boiling point temperature in Celsius scale = 100 ⁰C

In order to convert Celsius scale temperature to Kelvin scale temperature we use formula,

K = 273 + ⁰C 

K = 273 + 100 C

K = 373 K

The boiling point of ‘X’ in Kelvin is 373K

Problem  2: Convert 321 K to ⁰C.

Solution:

Given,

Temperature in Kelvin scale = 321 K

According to the relationship between Kelvin scale and Celsius scale,

C = k – 273

C = 321 – 273

C = 48 ⁰C

Value of temperature in Celsius scale is 48 ⁰C.

Problem 3: Convert 90 ⁰C to Kelvin.

Solution:

Given,

Temperature in Celsius scale = 90 ⁰C

According to the relationship between Kelvin scale and Celsius scale,

K = 273 + ⁰C 

K = 273 + 90 C

K = 363 K

Value of temperature in Kelvin scale is 363 K.

Problem 4: Convert -67 ⁰C to Kelvin.

Solution:

Given,

Temperature in Celsius scale = -67 ⁰C

According to the relationship between Kelvin scale and Celsius scale,

K = 273 + ⁰C 

K = 273 + (-67) C

K = 206 K

Value of temperature in Kelvin scale is 206 K.

Problem 5: A substance ‘A’ boils at temperature 66.5 ⁰C and has freezing point at -60 ⁰C. Find freezing and boiling point of substance ‘A’ in Kelvin?

Solution:

Given,

Boiling point temperature in Celsius scale = 66.5 ⁰C

Freezing point temperature in Celsius scale = -60 ⁰C

In order to convert Celsius scale temperature to Kelvin scale temperature we use formula,

K = 273 + ⁰C 

Boiling point:

K = 273 + 66.5 C

K = 339.5 K

The boiling point of ‘A’ in Kelvin is 339.5 K

Freezing point:

K = 273 + (-60) C

K = 213 K

The Freezing point of ‘A’ in Kelvin is 213 K

Problem 6: Convert 300 K to ⁰C.

Solution:

Given,

Temperature in Kelvin scale = 300 K

According to the relationship between Kelvin scale and Celsius scale,

C = k – 273

C = 300 – 273

C = 27 ⁰C

Value of temperature in Celsius scale is 27 ⁰C.

Problem 7: Convert 297 K to ⁰C.

Solution:

Given,

Temperature in Kelvin scale = 297 K

According to the relationship between Kelvin scale and Celsius scale,

C = k – 273

C = 297 – 273

C = 24 ⁰C

Value of temperature in Celsius scale is 24 ⁰C.