Contents
- zeroth law or fourth law??.
- Thermal equilibrium.
- Definition.
- Practical example.
- Significance.
Zeroth law or fourth law of thermodynamics??
The fourth law of thermodynamics is actually called the zero law of thermodynamics. This law was introduced after the three laws of thermodynamics. But the concept of zeroth law of thermodynamics is more fundamental that it should go before the other three laws.
since renaming the other three laws would lead to great confusion,they named this laws as zeroth law of thermodynamics.
What is thermal equilibrium?
Before diving into the definition of zeroth law of thermodynamics,one should know the concept called “thermal equilibrium“.
Thermal equilibrium is a state in which two or more objects or systems in thermal contact no longer exchange heat energy because they have reached the same temperature.
Example : Ice cubes in water.
When you put ice cubes into a glass of warm water, heat transfers from the water to the ice. Over time, the water cools, and the ice melts until both reach the same temperature.
Definition of zeroth law of thermodynamics:
If two thermodynamic systems are each in thermal equilibrium with the third, then they all are in thermal equilibrium with each other.
In other words consider three thermodynamic systems A, B, and C.
If systems, A and B, are each in thermal equilibrium with a third system C, then systems A and B are in thermal equilibrium with each other.
The Zeroth Law of Thermodynamics is a fundamental principle that defines temperature as a measurable property and establishes the basis for thermal equilibrium.
Also read : What is thermodynamic equilibrium?
Practical example of zeroth law of thermodynamics
Imagine you have three objects:
- Object A: A thermometer.
- Object B: A cup of hot coffee.
- Object C: A cup of room-temperature water.
First, place Object A (thermometer) in contact with Object B (hot coffee) and wait until the thermometer stabilizes(attaining thermal equilibrium). This indicates that A and B are in thermal equilibrium.
Next, place Object A (thermometer) in contact with Object C (room-temperature water). When the thermometer stabilizes again, it shows that A and C are also in thermal equilibrium.
Since the thermometer (Object A) is in thermal equilibrium with both the coffee (Object B) and the water (Object C), the Zeroth Law implies that if B and C were in contact, they would exchange heat until reaching thermal equilibrium. This principle is the basis for temperature measurement.
Significance
- The Zeroth Law is essential for:
- Defining temperature in a consistent and meaningful way.
- It makes temperature a scalar quantity since the system is in equilibrium.
- Justifying the use of thermometers as temperature measurement tools.
By providing the foundation for temperature measurement and comparison, the Zeroth Law is critical for all thermodynamic analyses.