**Description**: An experimental process, carried out at low pressures to find Charles's law. The "ideal gas" here is a mixture: air.

We will see that there is a relation of proportionality between the temperature and the pressure as long as the temperature is expressed in degrees Kelvin.

It is Charles' law.

**p1 / T1 = p2 / T2** (T in ° K)

Tk = Tc + 273

0 °C = 273,15 K

**absolute zero: 0 K = -273,15 °C**

**Definition**

__Kelvin__: The kelvin is the base unit of temperature in the International System of Units (SI), having the unit symbol K. Degree Celsius and kelvin have the same magnitude.