Question

The first law of thermodynamics is a statement of conservation of:

• A. Momentum
• B. Mass
• C. Energy
• D. Entropy

Hint:

Logic Tip: 1st Law = You can't get something for nothing (Energy is conserved). 2nd Law = You can't even break even (Entropy increases).

Answer 1

The Correct Option is C

Concept:
Thermodynamics is governed by four fundamental laws. The First Law is the foundational principle for all heat and work calculations in closed and open systems.

Step 1: The first law of thermodynamics explicitly states that energy can neither be created nor destroyed in an isolated system; it can only change forms (e.g., from chemical energy to heat to mechanical work).

Step 2: For a closed system undergoing a cycle or process, this is written as $\Delta U = Q - W$ (The change in internal energy equals the heat added to the system minus the work done by the system).

Step 3: Because the total amount of energy before a process must exactly equal the total amount of energy after the process, the law is fundamentally the Law of Conservation of Energy.

Step 4: * Conservation of Mass is a separate chemical principle (Lavoisier's law). * Conservation of Momentum relates to Newtonian mechanics. * Entropy is explicitly not conserved; the Second Law states that total entropy always increases.