# Basic units of thermodynamics

Mass——– kg.

Mole—— The mole is

the amount of substance that contains as many atoms (or molecules)

as there are atoms in 0.012 kg of carbon-12. Length—m.

Time: second

SI unit of temperature is Kelvin (abbreviated as K). The Kelvin is

defined as the fraction of 1/273.16 of the thermodynamic temperature of the

triple point of water. The relation between Kelvin and Celsius temperature is K

= C + 273.15 (The triple point of water is at 0.01 C).

Derived units: Force: 1 N = 1 kg m/s^{2}, pressure 1 Pa = 1

N/m^{2}, 1 bar = 10 Pa, 1 atm. = 101325 Pa.

In thermodynamics we are

concerned with absolute pressure.

Gauge pressure = absolute pressure –

atmospheric pressure.

Ordinary vacuum gauge pressure = atmospheric pressure –

absolute pressure.