The NDA (National Defence Academy) & CDS (Combined Defence Services) Exams are competitive national-level examinations conducted by the UPSC to recruit candidates for the Army, Navy, and Air Force.
To clear NDA/CDS, students must build strong foundations in Mathematics, General Science, Physics, Chemistry, General Knowledge, and English.
Chemistry topics, including Thermodynamics, often appear in the General Science section, testing conceptual clarity rather than deep numerical skill.
Class Overview: Thermodynamics (Chemistry – Class 9)
Introduction
Thermodynamics is the branch of science that deals with energy, heat, and work. It helps us understand how energy flows during chemical reactions and physical processes.
At the Class 9 level, thermodynamics focuses on basic ideas of heat transfer, temperature, expansion, and energy changes in matter.
These concepts form the building blocks for higher-level physics and chemistry, and they are important for NDA/CDS exam preparation.
Subtopics to be Covered
1. Basic Concepts of Heat and Temperature
- Meaning of heat and temperature
- Difference between heat and temperature
- Measurement and units (°C, K, J)
2. Modes of Heat Transfer
- Conduction – heat transfer through solids
- Convection – heat transfer in liquids and gases
- Radiation – heat transfer without a medium
- Everyday examples (cooking, sea breeze, thermos flask)
3. Effects of Heat
- Thermal expansion: expansion of solids, liquids, gases
- Practical applications: railway tracks, thermometer, bridges
4. Change of State
- Melting, freezing, evaporation, condensation, sublimation
- Latent heat: latent heat of fusion & vaporization
- Heating curves and cooling curves
5. Energy and Work in Thermodynamics (Basic Idea)
- Internal energy
- Work done by heat
- Concept of specific heat capacity
- Application: why water is used as a cooling agent
6. Simple Calorimetry
- Heat gained = Heat lost
- Mixture problems (basic level)
- Real-life uses: calorimeters, energy in food
7. Everyday Applications of Thermodynamics
- Pressure cooker
- Refrigerator
- Heat insulation in homes
- Why metal feels colder than wood
Conclusion
Thermodynamics helps us understand how heat energy behaves in our daily lives and in scientific reactions.
For NDA CDS 1 2026 preparation, mastering these foundational concepts will strengthen your basics for more advanced physics and chemistry topics. Learning thermodynamics at this level builds a clear understanding of energy flow, heat transfer, and states of matter, which are essential both for the exam and real-world scientific thinking.
