Temperature Scales

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Kelvin and Celsius scales are used to express temperature
The change in temperature of a system is the same when expressed with the Kelvin or Celsius scales

Temperature Scales

In the field of thermodynamics, the concept of temperature plays a crucial role in understanding the behavior of systems The Kelvin and Celsius scales are two commonly used temperature scales to express the thermal state of a system.

Kelvin Scale

The Kelvin scale, also known as the absolute temperature scale, is named after the Scottish physicist William Thomson, 1st Baron Kelvin. It is based on the concept of absolute zero, which is the lowest possible temperature where all molecular motion ceases. Absolute zero is defined as 0 Kelvin (0 K).

The Kelvin scale has a linear relationship with temperature, where each unit is equal to the size of one Celsius degree. Therefore, a change of 1 Kelvin is equivalent to a change of 1 degree Celsius. This property makes the Kelvin scale particularly useful for scientific calculations, as it simplifies temperature conversions.

Celcius Scale

The Celsius scale, also known as the centigrade scale, is named after the Swedish astronomer Anders Celsius. It is based on the properties of water, specifically the freezing and boiling points. The Celsius scale assigns the freezing point of water at sea level to be 0 degrees Celsius (0 °C) and the boiling point of water at sea level to be 100 degrees Celsius (100 °C).

The Celsius scale is widely used in everyday life, as it provides a convenient reference point using the properties of water. However, it is important to note that the Celsius scale is not an absolute temperature scale, as it does not have an absolute zero reference point like the Kelvin scale.

Relationship Between Celcius and Kelvin

The change in temperature between each point on the Kelvin scale is equal to the same change in temperature on the Celsius scale. The difference between boiling point and freezing point of water is 100 degrees on both scales. (Photo by A. Forgue, image may be copied, modified, and distributed freely.)

Celcius and Kelvin have a linear relationship. This means that the change in 1 K is equal to a change in 1°C

The Kelvin and Celsius scales are directly related to each other through a simple mathematical relationship. The conversion between the two scales can be done using the following equation:

T(K) = T(°C) + 273.15

where T(K) represents the temperature in Kelvin and T(°C) represents the temperature in Celsius.

This equation shows that a temperature in Celsius can be converted to Kelvin by adding 273.15. Similarly, a temperature in Kelvin can be converted to Celsius by subtracting 273.15.

For example, let's consider a temperature of 25 degrees Celsius (25 °C). To convert it to Kelvin, we can use the equation:

T(K) = 25 °C + 273.15 = 298.15 K

Conversely, if we have a temperature of 350 Kelvin (350 K) and want to convert it to Celsius, we can use the equation:

T(°C) = 350 K - 273.15 = 76.85 °C

KEY IDEA: This relationship allows us to express the same change in temperature using either the Kelvin or Celsius scales. Since a change of 1 Kelvin is equivalent to a change of 1 degree Celsius, the magnitude of the change in temperature remains the same regardless of the scale used.

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