Question

Which of the following are the correct statements about laws of thermodynamics:
A. The first law does not indicate the direction in which the change can occur.
B. The first law indicates the direction in which the change can occur.
C. The second law does not indicate the direction in which the change occurs.
D. The second law indicates the direction in which the change can occur.
Choose the correct answer from the options given below:

• A. A and D only
• B. A, B and D only
• C. A, B, C and D
• D. B, C and D only

Hint:

Think of it this way: The First Law says "You can't win" (you can't create energy from nothing). The Second Law says "You can't even break even" (you can't return to the same energy state without increasing disorder/entropy). The Second Law is all about the direction of change.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
This question requires an understanding of the scope and limitations of the First and Second Laws of Thermodynamics, specifically concerning the directionality of thermodynamic processes.
Step 2: Detailed Explanation:
Statement A and B: The First Law of Thermodynamics is the law of conservation of energy (\(\Delta U = Q - W\)). It states that energy cannot be created or destroyed. However, it places no restriction on the direction of a process. For example, the First Law would allow heat to flow spontaneously from a cold body to a hot body, as long as energy is conserved. Since this does not happen in reality, we know the First Law does not specify the direction of spontaneous change.
Therefore, statement A is correct and statement B is incorrect.
Statement C and D: The Second Law of Thermodynamics was formulated precisely to address the limitation of the First Law. The Second Law introduces the concept of entropy and states that for any spontaneous process in an isolated system, the total entropy must increase. This provides a clear "arrow of time" or direction for physical processes. A process will only occur spontaneously if it leads to an increase in the total entropy of the universe.
Therefore, statement D is correct and statement C is incorrect.
Step 3: Final Answer:
The correct statements are A and D.