Units & unit conversions
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Below is a short list of quantities for thermodynamic measurements, together with their SI units and symbols, compliant with IUPAC (International Union of Pure and Applied Chemistry) terminology.

Physical quantity

Symbol

SI unit

Heat

Q

J (Joule)

Thermodynamic temperature

T

K (Kelvin)

Celsius temperature

θ, t

C (Celsius)

Internal energy

U

J

Enthalpy

H

J

Standard reaction enthalpy

ΔH

J mol-1

Entropy

S

J K-1

Heat capacity at constant pressure

Cp

J K-1

Specific heat capacity at constant pressure

cp

J K-1 g-1

Heat capacity at constant volume

Cv

J K-1

Specific heat capacity at constant volume

cv

J K-1 cm-3

Heat flow rate

Φ= dQ/dt

W (watt)

 

Other units used to measure heat, with their corresponding SI equivalents:

Physical quantity

Unit

Equivalent in SI units

Heat

calorie (cal)

4.184 J

Heat

British Thermal Unit (BTU)

1055.06 J

Heat

Erg (CGS unit)

10-7 J

Temperature

Fahrenheit F

0.56 K

 

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