Thermodynamics Characteristics

Thermodynamic characteristics are detrimental factors to describe the state of a system. A thermodynamic property is a particularity or a characteristic that allows the changes of the work system. Thermodynamics is a part of physics that establishes relations between work, heat and different forms of energy.

Thermodynamic system

A system means the part of the universe in which observations are carried out.

An assemblage of large molecules of gas molecules is defined as a thermodynamic system. The pressure P, volume V, Heat content Q, Temperature T are called the thermodynamic parameters. They determine their thermodynamic characters.

A surrounding can be defined as a part of the universe other than the system.

There are generally three types of systems:

1. An Open system is a system where the exchange of energy and matter occurs between the system and the external region. 

E.g., water in a saucepan. 

1. A closed system is created when there is no exchange of matter, but the exchange of energy is possible. There is no transfer of mass.

E.g., water bottle.

1. When no energy exchange or matter takes place with the surroundings, it is called an isolated system. There is no to and fro exchange of energy.

E.g., thermo-flask.

Thermodynamic property

The physical properties can be described using various thermodynamic characteristics such as pressure, temperature, volume, enthalpy, etc.

Intensive and extensive properties:

Intensive property can be defined as any property of a system that does not depend on the actual quantity of matter contained or on the components in the system.

Melting point, pressure, boiling point, density, etc., are examples of Intensive properties. Intensive properties are additive.

The extensive property is the property of a system dependent upon the actual quantity of matter contained in the system. 

Mass, volume,  internal energy, number of moles, enthalpy, etc., are some examples of extensive properties. It is an additive property of the system. Extensive properties are those which are non-additive. Volume is an example of extensive property.

There are certain features associated with these properties:

• Suppose a system has two or more two substances. In that case, the extensive property depends on independent variables such as temperature and volume and the moles of different constituents present in the system.
• An extensive property becomes an intensive property expressed in terms of several moles or grams. Density is an example of this. Volume and Mass are defined as extensive properties.

But the density is calculated in mass per unit volume which is an intensive property.

• It is also noted that the result of sum, product, as well as the ratio of intensive properties, are known as intensive properties. 

Homogeneous and heterogeneous system

A system is said to be homogeneous when all the constituents are present in the same phase and show uniform throughout the system.

Saline water is said to be homogeneous.

A mixture is generous to be heterogeneous when it consists of two or more phases of constituents and the composition is not uniform.

A mixture of insoluble solids in water is an example.

Thermodynamic processes

1. Isothermal process: When a reaction is carried out at a constant temperature, the process is said to be isothermal. For such an isothermal process, dT = 0, where dT is denoted as the change in temperature.
2. An Adiabatic process is when no transfer of heat between the system and surroundings takes place.
3. The isobaric process is carried out at constant pressure and it is said to be isobaric. 

            That means, dP = 0

1. An isochoric process is a process that is carried out at constant volume.
2. A process is said to be cyclic if a system undergoes a series of changes and finally returns to its initial state.
3. Reversible Processes are processes in which a tiny change can reverse the process. The change is called reversible.
4.  Internal Energy can be defined as the sum of all the forms of energies that a system can possess.

In thermodynamics, internal energy transfer increases when heat or temperature passes into the system or when work is done on or by the system.

Zeroth law of thermodynamics or law of thermal equilibrium

The law states that if the two systems are in thermal equilibrium with a third system, they are also in thermal equilibrium. 

Temperature is used to know if the system is in thermal equilibrium or not.

The first law of thermodynamics

Energy can neither be created nor destroyed, although it can be converted from one form to the other.

Mathematically it can be represented as, 

ΔU = q + W

where ΔU = internal energy change

q = heat added to the system

W = work added to the system

The second law of thermodynamics

This law states that heat energy cannot be transferred from a body with a lower temperature to a body with a higher temperature without adding any form of energy.

Quasi-static process

A process in which the system remains close to an equilibrium state at each time is termed as the quasi-static process or quasi-equilibrium process.

Conclusion

Studying the properties and characteristics of thermodynamic properties is important because they help us use the maximum amount of energy.Engineers and chemists use thermodynamic properties to build engines that maximise heat energy efficiency.