Thermodynamics | NCERT Chemistry | NEET 2025 CHEMISTRY | NEET 2025 | Diksha Kaushal

Introduction

This tutorial provides a comprehensive guide to the fundamental principles of thermodynamics as covered in the NCERT Chemistry curriculum, specifically aimed at NEET 2025 aspirants. Understanding these concepts is essential for mastering chemistry problems in competitive exams. This step-by-step guide will break down key topics such as the laws of thermodynamics, enthalpy, entropy, and Gibbs free energy, making them easier to grasp and apply.

Step 1: Understand the First Law of Thermodynamics

• Definition: The first law states that energy cannot be created or destroyed, only transformed from one form to another.
• Key Equation:
  • ΔU = Q - W
    • Where ΔU is the change in internal energy, Q is the heat added to the system, and W is the work done by the system.
• Practical Tip: Consider real-world examples such as heat engines or refrigerators to see the first law in action.

Step 2: Grasp the Second Law of Thermodynamics

• Definition: This law states that the total entropy of an isolated system can never decrease over time.
• Key Concepts:
  • Entropy: A measure of disorder or randomness in a system.
  • Heat Transfer: Heat naturally flows from hot to cold objects, increasing the overall entropy.
• Real-World Application: Understand how this principle applies to everyday phenomena, like ice melting in a warm room.

Step 3: Explore Enthalpy

• Definition: Enthalpy (H) is a measure of the total heat content of a system.
• Key Equation:
  • ΔH = ΔU + PΔV
    • Where P is pressure and ΔV is the change in volume.
• Common Pitfalls: Remember that enthalpy changes during chemical reactions can indicate whether a reaction is exothermic (releases heat) or endothermic (absorbs heat).

Step 4: Delve into Gibbs Free Energy

• Definition: Gibbs free energy (G) indicates the maximum reversible work that can be performed by a thermodynamic system at constant temperature and pressure.
• Key Equation:
  • ΔG = ΔH - TΔS
    • Where T is the temperature in Kelvin and ΔS is the change in entropy.
• Practical Advice: Use Gibbs free energy to predict the spontaneity of reactions:
  • If ΔG < 0, the reaction is spontaneous.
  • If ΔG > 0, the reaction is non-spontaneous.

Step 5: Connect Concepts to NEET Questions

• Exam Strategy: Familiarize yourself with common types of questions related to thermodynamics that may appear in the NEET exam.
• Practice Problems: Solve previous years' NEET questions to reinforce your understanding of thermodynamic principles.

Conclusion

Understanding the principles of thermodynamics is crucial for NEET preparation. Focus on the first and second laws, along with concepts like enthalpy and Gibbs free energy. Regular practice with real-world applications and NEET-style questions will enhance your grasp of these topics. As you study, keep linking theoretical concepts to practical scenarios to solidify your knowledge for the exam.