According to Kinetic Theory, the temperature of a gas is a direct measure of the average kinetic energy of its particles. As temperature decreases, particles lose energy and move more slowly.
As particles slow down, the frequency and force of their collisions with container walls decrease, leading to a drop in gas pressure.
By extrapolating the pressure-temperature relationship of a gas downward, scientists identified that pressure would theoretically reach zero at , marking the point where all motion stops.
To convert from Celsius to Kelvin, you must add to the Celsius value. The formula is:
To convert from Kelvin to Celsius, you must subtract from the Kelvin value. The formula is:
When performing these conversions, it is helpful to remember the reference point: (the freezing point of water) is equal to .
| Feature | Celsius Scale | Kelvin Scale |
|---|---|---|
| Zero Point | Freezing point of water () | Absolute zero () |
| Negative Values | Possible and common | Impossible |
| Scientific Use | General purpose/weather | Thermodynamics/Gas laws |
Always check units: If a physics problem provides a temperature in Celsius, your first step should almost always be to convert it to Kelvin before using it in an equation.
Sanity Check: Remember that a Kelvin temperature can never be negative. If your calculation results in a negative Kelvin value, you have likely reversed the conversion formula.
Change vs. Absolute: Be careful to distinguish between a 'temperature' and a 'change in temperature'. A change of is exactly the same as a change of , so no conversion is needed for temperature differences.
