- The zeroth law of thermodynamics was established after the first and second law of thermodynamics and it is the basic fundamental law of physical chemistry so it was named as zeroth law of thermodynamics.
- Thermodynamics is the branch of physical chemistry which deals with the study of thermal change in properties of the systems and their behaviour.
- As we all know that, temperature flows from high temperature to lower temperature. Let us suppose one body is at high temperatures and another body is in contact with the first body which is at lower temperature. Then there will be temperature difference between these two bodies and hence there will be transfer of heat takes place. And the transfer of heat is possible till both the bodies become at the same temperature. When both bodies become at same temperature then we can say that that bodies are in thermal equilibrium.
- So, the zeroth law of thermodynamics is based on the thermal equilibrium of the systems.
Statement:
According to zeroth law of thermodynamics, if the two bodies P and Q are in thermal equilibrium and the two bodies P and R are also in thermal equilibrium then the bodies Q and R are also in thermal equilibrium.
This is like the equality property in mathematics.
Explanation:
- We all know that; heat transfer takes place from high temperature region to low temperature region always. Hence, if the bodies are in thermal equilibrium that means they are having the same temperature and there is no temperature difference.
- Thus, temperature is the physical quantity which measures the hotness or coldness of the body from which we decide the heat content of the body.
- The system whose temperature is remain constant throughout the process such process is called as the isothermal process.
Applications:
- Zeroth law is mainly used for measuring temperature or temperature difference between the different bodies.
- If the bodies are in thermal equilibrium, then there will be no heat transfer takes place and temperature of the system become constant.
- Also, in thermometer zeroth law of thermodynamics is used to measure temperature. As the temperature get increased then there will be expansion of mercury in the tube takes place but the area of the tube till is same.
- So due to expansion and less area the height of the mercury level in the thermometer increases. And increase in height indicates us that there is high temperature or we can note the particular value of the temperature.
- Thus, zeroth law is most important in measuring temperature of the different bodies.