How do I convert from Kelvin to Celsius?
Take away 273.15. A room at 300 K is 26.85 °C, and water boils at 373.15 K, which is 100 °C.
The two scales use exactly the same size of degree, so there's no multiplying involved – only the starting point moves. Kelvin starts at absolute zero, which makes 0 K equal to -273.15 °C.
Liquid nitrogen sits at about 77 K, or -196 °C. Kelvin doesn't take a degree sign either, so it's 300 K, not 300 °K.
About Celsius
Celsius is the most commonly used temperature scale in the world. The Celsius scale (known as the centigrade in some instances) is named after the Swedish astronomer Anders Celsius. It is based on the freezing and boiling points of water at standard atmospheric pressure making 0°C the freezing point and 100°C the boiling point.
The Celsius scale is normally found in weather forecasts, household temperatures and cooking in most countries with the notable exception of the United States.
About Kelvin
Kelvin is an absolute temperature measurement defined in the International System of Units (SI). It is named after the Scottish physicist William Thomson (Lord Kelvin) who studied the field of thermodynamics. The Kelvin scale is based on absolute zero; the point at which all molecular motion ceases.
Unlike most other temperature scales, Kelvin does not have degrees as it is not a relative scale. The Kelvin scale is often used in physics, chemistry, and cosmology.
One advantage of Kelvin is that it does not have negative values making some calculations easier. This is useful in science calculations involving gases as it relates to the kinetic energy of molecules.
What happens at absolute zero (0K)?
At absolute zero, 0 Kelvin (0K) or -273.15 degrees Celsius, the temperature is at the lowest possible point anything can possibly be. At this temperature the kinetic energy of atoms and molecules is zero causing them to come to a complete standstill. All molecular motion ceases and matter becomes still.
Several amazing phenomena occur here. As there is no molecular motion there is no heat energy and this has significant implications for the physical properties of the substance. For example, materials become very brittle and their electrical resistance becomes zero. Gases and liquids freeze into solids.
Scientists have never cooled anything down to absolute zero. However they have been able to see the effects of approaching absolute zero. This has provided insights into the behavior of matter and have led to the understanding of superconductors and Bose-Einstein condensates.
Why can you not go below -273.15°C?
The temperature -273.15°C is known as absolute zero and it is the lowest possible temperature that can exist in the universe. At this point all molecular motion ceases and no further fall in temperature is possible since the kinetic energy of particles is at zero and they come to a complete standstill.
The Kelvin and Rankine scales start at absolute zero.
Going below -273.15°C or 0K is impossible because it contradicts the laws of thermodynamics. The energy of particles in an object decreases as they lose kinetic energy and their ability to move. At absolute zero the particles have no energy to give up making any further fall in temperature impossible as this would require them to have negative energy which is not possible.
Why can't you get a negative Kelvin value?
Kelvin is an absolute measurement of temperature meaning it starts at absolute zero, the lowest possible temperature in our universe. Absolute zero is 0 Kelvin(K) or -273.15 degrees Celsius(°C). The Kelvin scale is based on the average kinetic energy of particles in a substance.
You cannot have a negative Kelvin value because at 0K there is no kinetic energy in the particles and are at their lowest possible state of motion. It is impossible for a system to have less energy than zero.
Negative Kelvin would imply that a system has a negative thermal energy which breaks the principles of thermodynamics. It is important to remember that negative temperatures exist in other temperature scales such as the Celsius and Fahrenheit.
Why is Kelvin quoted as K and not °K?
This abbreviation of K is based on the fact that Kelvin is an absolute temperature scale where zero Kelvin (0K) is absolute zero. Celsius and Fahrenheit which have arbitrary zero points based on freezing and boiling points of water are relative and have degrees of relation whereas the Kelvin scale is based on the absolute thermodynamic temperature.
By omitting the degree symbol, it reminds us that Kelvin is not a relative measurement but a unit of measurement on its own. The use of "K" instead of "°K" for Kelvin was decided as an SI convention to reserve the degree symbol for relative temperature scales.