# Properties Of Thermodynamics

Thermodynamics: Different forms of energy and work can be related to each other with the help of thermodynamics which is one of the branches of Physics.

There are four laws that are base of thermodynamics and their applications:

• Zeroth law of thermodynamics: For any two given systems which are in thermal equilibrium with the third, are in thermal equilibrium with each other. When the definition of temperature became more important with this law, it was considered as one of the laws of thermodynamics. This law is used in the construction of thermometers.
• First law of thermodynamics: For an isolated system, the internal energy remains constant.
• Second law of thermodynamics: Heat flow is not spontaneous from colder place to hotter place. Application of this law is in industrial refrigeration systems like deep freezers and AHUs (Air Handling Units).
• Third law of thermodynamics: When a system is at absolute zero, entropy is at its minimum value and all processes are ceased.

Properties of thermodynamics:

• Extensive properties: Property of a physical quantity whose value is dependent or proportional to the amount of substance measured.

Example: enthalpy (H), entropy(S).

• Intensive properties: Property of a physical quantity whose value is independent of the amount of substance measured.

Example: viscosity, temperature(T), density(ρ)

Enthalpy (H):

It is a sum of internal energy and product of pressure and volume whose SI (International System of Units) unit is joule and BTU (British thermal unit) is calorie. It is a state function ie; it is independent of the path through which the final state of the system has been achieved. Change in enthalpy is represented as ΔH. For endothermic reactions ΔH is positive and for exothermic reactions ΔH is negative. For ideal gases and incompressible solids and liquids H does not depend on pressure.

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