The study of the flow of heat or any other from of energy into or out of a system as it undergoes a plysical or chemical transformation, is called Thermodynamics.
In studying and evaluation the flow of energy into or out of a system, it will be useful to consider changes in certain properties of the system. These properties include temperature, pressure, volume and concentration of a system. Measuring the changes in these properties from the initial state to the final state, can provide information concerning changes in energy and related quantities such as heat and work.
The Three Empirical Lows
The study of thermodynamics is based on three broad generatizations derived from well established experimental results.
These generalization are known as the First, Second and Third law of thermodynamics.
These laws have stood the test of time and are independent of any theory of the atomic or molecules structure.
Scope of Thermodynamics
- Most of the important laws of physical Chemistry, including the van't Hoff law of lowering of vapour pressure, Phase Rule and the Distribution laws, can be derived from the laws of thermodynamics.
- It tells whether a perticular physical or chemical changes can occur under a given set of conditions of temperature, pressure and concentration.
- It also helps in predicting how far s physical or chemical change can proceed, until the equilibrium conditions are established.
Limitations of Thermodynamics
- Thermodynamics is applicable to microscopic systems consisting of matter in bulk and not to microscopic systems of individual atoms or molecules. It ignores the internal structure of atoms and molecules.
- Thermodynamics does not botter about the time factor. That is, does not 🚫 tell anything regarding the rate of physical change or a chemical reaction. It is concerned only with the initial and the final states of the system.
Thermodynamics Terms and Basic Concepts
An important part of the study of thermodynamics is few terms and definitions which must be understood clearly.
System, Bonding, Surroundings
A system is part of the universe which is under thermodynamics study and the rest of the universe is surroundings.
The real or imaginary, surface separating the system from the surroundings is called the boundary.
In experiment work, a specific amount of one or more substances constitutes the system. Thus 0.200 kg of water contained in a flask and the air in contact, are the surroundings.
Similarly I mole of oxygen confined in a cylinder fitted with a piston, is a thermodynamics system. The cylinder and the piston and all other objects outside the cylinder, from the surroundings.
Here the boundary the system (oxygen) and the surroundings (cylinder and piston) is clearly defined.
Homogenous and Hatrogeneous System:
When a system is uniform throughout, it is called a Homogeneous System.
Examples: a pure single solid, liquid or gas, mixtures of gases, and true solution of a solid in a liquid. A homogeneous system is made of one phase only. A phase of difined as a homogeneous, physically distinct and mechanically portion of a system.
Heterogeneous: A heterogeneous system is one which consists of two or more phase. In other words it is not uniform throughout. Examples of Hatrogeneous systems are: ice in contact with water, ice in contact with vapour etc. Here ice, water and vapour constitute separate phases.
