Entropy is an important concept in thermodynamics. The term entropy is used in different fields ranging from classical thermodynamics, statistical physics and even information science. In addition to the application of entropy in Physics and Chemistry, it can be applied to biological systems and their relation to life, sociology, weather science, climate change and many other fields.
In general, the definition of entropy is given as the measure of the disorder of the system. The concept of entropy was explained by scientist Rudolf Clausius in the year 1850. In addition, to the general definition of entropy, there is a thermodynamic definition and a statistical definition for entropy.
The thermodynamic definition of entropy is given in terms of the properties such as temperature, pressure and heat capacity. The statistical definition of entropy was in terms of the statistics of the molecular motion of the system.
The value of entropy increases when there is an increase in the irregularity of the system. In the case of a chemical reaction, if the reactants break into more products, there will be an increase in the entropy. The entropy increases if the temperature of the system increases.
Properties of Entropy
- Entropy is a thermodynamic function.
- It depends on the state of the system. Therefore, it can be called a state function.
- The alphabet “S” is used to represent entropy
- Entropy is measured in J/Kmol in the SI system
- The CGS unit of entropy is cal/Kmol
- It is an extensive property
Entropy and Thermodynamics
The different laws of thermodynamics can be compared with the entropy.
First law of thermodynamics: The first law of thermodynamics is based on the law of conservation of energy. The first law of thermodynamics states that the internal energy of the system is the difference between the heat added to the system and the work done by the system.
Entropy increases when the number of moles of gaseous products increases more than the reactants.
Second law of thermodynamics: According to the second law of thermodynamics, heat cannot flow by itself from a colder body to a hotter body. In terms of entropy, the law states that the entropy of the universe will increase continuously.
Third law of thermodynamics: As the temperature approaches absolute zero, the entropy of the crystalline solid approaches zero. The limitation of this law is that many of the solids do not have zero entropy at absolute zero.
When there is an increase in the temperature of the body, there will be an increase in the dimension of the body. This property is known as thermal expansion. There are different types of thermal expansion.
Types of thermal expansion
Linear Expansion: The linear expansion is the increase in the length of the object due to heat.
Volume Expansion: Volume expansion is the change in the volume of the object due to an increase in temperature.
Area Expansion: The change in the area of the object due to a change in temperature is called area expansion.