Which law of thermodynamics introduces the concept of entropy ?

Options

A. First law
B. Zeroth law
C. Third law
D. Second law

Answer

To solve the question "Which law of thermodynamics introduces the concept of entropy?", we can follow these steps:

### Step 1: Understand the Laws of Thermodynamics
The laws of thermodynamics are fundamental principles that describe how energy behaves in physical systems. There are four main laws: Zeroth, First, Second, and Third.

### Step 2: Review the First Law of Thermodynamics
The First Law of Thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another. This law does not introduce the concept of entropy.

**Hint:** The First Law focuses on energy conservation.

### Step 3: Review the Second Law of Thermodynamics
The Second Law of Thermodynamics introduces the concept of entropy. It states that in an isolated system, the total entropy can never decrease over time. This law implies that natural processes tend to move towards a state of maximum disorder or randomness, which is quantified by entropy.

**Hint:** The Second Law is about the direction of processes and the concept of disorder.

### Step 4: Review the Zeroth Law of Thermodynamics
The Zeroth Law establishes thermal equilibrium between systems. It states that if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. This law does not relate to entropy.

**Hint:** The Zeroth Law is about thermal equilibrium, not entropy.

### Step 5: Review the Third Law of Thermodynamics
The Third Law of Thermodynamics states that as the temperature of a system approaches absolute zero, the entropy of a perfect crystal approaches zero. While it involves entropy, it does not introduce the concept.

**Hint:** The Third Law deals with entropy at absolute zero.

### Conclusion
Based on the analysis of the laws, the law of thermodynamics that introduces the concept of entropy is the **Second Law of Thermodynamics**.

**Final Answer:** The answer is the Second Law of Thermodynamics (Option D).