Thermodynamics
Zeroth Law of Thermodynamics
Statement: If two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.
Explanation: This law defines temperature and establishes that if two objects are the same temperature as a third object, they must also be the same temperature as each other.
First Law of Thermodynamics
Explanation: This law restates the principle of energy conservation. For instance, heating a gas can result in piston movement (work) and increased temperature (internal energy).
Second Law of Thermodynamics
Statement: The total entropy of an isolated system always increases over time.
Explanation: Natural processes favor increased disorder (entropy). Heat flows from hot to cold, not the reverse, explaining why processes are irreversible.
Third Law of Thermodynamics
Statement: As the temperature of a system approaches absolute zero (0 K), the entropy of the system approaches a minimum value, typically zero.
Explanation: At very low temperatures, disorder reduces. At absolute zero, a system would theoretically have zero entropy, though it’s practically unattainable.
MCQ Quiz
- The Zeroth Law of Thermodynamics is related to:
Heat transfer
Temperature measurement ✅ - The First Law states:
Entropy always increases
Energy is conserved ✅ - The Second Law explains:
Heat flows from cold to hot
Heat flows from hot to cold ✅ - The Third Law relates to:
Absolute zero ✅
Energy conservation - Which law introduces the concept of entropy?
Zeroth Law
Second Law ✅
True / False
- Energy can be created in a closed system. – False ❌
- Entropy of an isolated system decreases over time. – False ❌
- The Zeroth Law helps define temperature. – True ✅
- Absolute zero is practically attainable. – False ❌
FAQs
What is the importance of the First Law?
It ensures that all energy changes in a system are accounted for, forming the basis for energy conservation in physics and chemistry.
Why is the Second Law crucial?
It explains why natural processes are irreversible and why heat engines have limited efficiency.
Is the Third Law applicable in real life?
Yes, it guides low-temperature physics and cryogenics, though absolute zero is unattainable.
