Question

The first law of thermodynamics is a statement of
• Conservation of momentum
• Conservation of energy
• Conservation of mass
• The law of entropy

• A. Conservation of momentum
• B. Conservation of energy
• C. Conservation of mass
• D. The law of entropy

Hint:

First law of thermodynamics: \[ Q=\Delta U+W \] It is simply the law of: \[ \boxed{ \text{Conservation of energy} } \]

Answer 1

The Correct Option is B

Concept: The first law of thermodynamics establishes the relationship between:
• Heat supplied
• Internal energy
• Work done It is fundamentally based on: \[ \boxed{ \text{Conservation of energy} } \]

Step 1: State the first law of thermodynamics. The first law states: “Heat supplied to a system is used partly to increase its internal energy and partly to do external work.” Mathematically: :contentReference[oaicite:6]{index=6} where:
• \(Q\) = heat supplied
• \(\Delta U\) = change in internal energy
• \(W\) = work done

Step 2: Understand the meaning physically. Energy supplied as heat does not disappear. It gets converted into:
• Internal energy
• Mechanical work Thus total energy remains conserved. Hence: \[ \boxed{ \text{First law is conservation of energy} } \]

Step 3: Analyze the options.
• Conservation of momentum \(\rightarrow\) unrelated
• Conservation of energy \(\rightarrow\) correct
• Conservation of mass \(\rightarrow\) incorrect
• Law of entropy \(\rightarrow\) second law of thermodynamics

Step 4: Choose the correct answer. Therefore: \[ \boxed{ \text{First law of thermodynamics is conservation of energy} } \] Hence the correct option is: \[ \boxed{(2)} \] Final Conclusion: The first law of thermodynamics expresses: \[ \boxed{ \text{Conservation of energy} } \] Hence, the correct answer is: \[ \boxed{(2)} \]