NCERT Class 11 Chemistry Chemistry Part-I: Chapter 5 — Thermodynamics
This chapter introduces Thermodynamics, a physical theory dealing with energy transformations in macroscopic systems. It covers fundamental concepts like system, surroundings, and boundaries, and classifies systems into open, closed, and isolated based on matter and energy exchange. The chapter aims to explain energy changes in chemical reactions, spontaneity, and the extent to which reactions proceed. Key learning objectives include understanding internal energy, work, heat, the first law of thermodynamics, state functions (U, H), standard states, enthalpy changes, Hess's law, spontaneous processes, entropy, and Gibbs energy. This knowledge is crucial for understanding chemical reactions and their energy implications in CBSE Chemistry.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 11 |
| Subject | Chemistry |
| Book | Chemistry Part-I |
| Chapter | Chapter 5 — Thermodynamics |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 5 minutes |
| Word count | 838 |
Learning outcomes
- Explain the terms system and surroundings.
- Differentiate between open, closed, and isolated systems.
- Explain internal energy, work, and heat.
- State and apply the first law of thermodynamics.
- Define and apply state functions like internal energy (U) and enthalpy (H).
- Understand spontaneity and Gibbs energy.
Vocabulary
| Word | Meaning |
|---|---|
| Thermodynamics | The study of energy transformations in macroscopic systems. |
| System | That part of the universe where observations are made. |
| Surroundings | The remaining universe that constitutes everything other than the system. |
| Boundary | The wall that separates the system from the surroundings. |
| Open System | A system where there is an exchange of energy and matter with the surroundings. |
| Closed System | A system where there is no exchange of matter, but exchange of energy is possible with the surroundings. |
| Isolated System | A system where there is no exchange of energy or matter with the surroundings. |
| Internal Energy (U) | The total energy contained within a thermodynamic system. |
| Work | Energy transferred when a force moves an object over a distance. |
| Heat | Energy transferred due to a temperature difference. |
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Practice questions
- What is the difference between a system and its surroundings? Answer: The system is the part of the universe where observations are made, while the surroundings are everything else in the universe that is not the system.
- Describe an open system. Answer: An open system allows both energy and matter to be exchanged with its surroundings.
- What characterizes a closed system? Answer: A closed system allows energy exchange but not matter exchange with its surroundings.
- Give an example of an isolated system. Answer: An example is a perfectly insulated thermos flask, where neither heat nor matter can enter or leave.
Frequently asked questions
What is thermodynamics?
Thermodynamics is the branch of physics that deals with heat, work, temperature, and energy, and their interrelations.
What is the difference between a system and surroundings in thermodynamics?
The system is the specific part of the universe being studied, while the surroundings are everything else outside the system.
What are the three types of thermodynamic systems?
The three types are open systems (exchange energy and matter), closed systems (exchange energy only), and isolated systems (exchange neither energy nor matter).
What is the first law of thermodynamics?
The first law of thermodynamics states that energy cannot be created or destroyed, only converted from one form to another.
What are state functions in thermodynamics?
State functions are properties of a system that depend only on its current state, not on the path taken to reach that state, such as internal energy (U) and enthalpy (H).
What does spontaneity mean in chemistry?
Spontaneity refers to a process that occurs naturally under a given set of conditions without external intervention.
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NCERT Class 11 Chemistry — Chemistry Part-I — Chapter 5 — Thermodynamics. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.