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Revision Notes
Thermodynamics — Revision Notes
Punjab Board · Class 11 · Chemistry
Thermodynamics revision notes for Punjab Board Class 11 Chemistry: 4 topics in quick points. Part of the Punjab Board Class 11 Chemistry syllabus.
45 questions25 flashcards5 formulas & key relations5 concepts
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Key Topics to Revise
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1. Basic Thermodynamic Terms: System, Surroundings, and Types of Systems
- The SYSTEM is the part of the universe under study. The SURROUNDINGS is everything else. Together, System + Surroundings = Universe.
- OPEN SYSTEM: Both matter AND energy can be exchanged with surroundings. Example: Reactants in an open beaker.
- CLOSED SYSTEM: Only ENERGY can be exchanged, NOT matter. Example: Reactants in a sealed copper vessel.
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2. Internal Energy, Work, Heat, and the First Law of Thermodynamics
- INTERNAL ENERGY (U) is the total energy of the system — sum of all kinetic and potential energies of all particles.
- Internal energy is a STATE FUNCTION. We can only measure CHANGE in internal energy (ΔU), not absolute U.
- WORK (w): When external pressure pex compresses a gas from Vi to Vf, work done on system = w = −pex × ΔV.
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3. Enthalpy (H), Heat Capacity, and Relationship Between ΔH and ΔU
- ENTHALPY (H) = U + pV. It is a state function defined to handle constant pressure processes.
- At constant pressure: ΔH = qp. Heat absorbed at constant pressure equals change in enthalpy.
- Relationship: ΔH = ΔU + ΔngRT, where Δng = moles of gaseous products − moles of gaseous reactants.
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4. Enthalpy Changes: Standard Enthalpy, Formation, Combustion, Hess's Law
- STANDARD STATE: Pure form of a substance at 1 bar pressure and specified temperature (usually 298 K). Denoted by superscript ⊖.
- STANDARD ENTHALPY OF REACTION (Δr H⊖): Enthalpy change when reaction occurs with all substances in standard states.
- STANDARD ENTHALPY OF FORMATION (Δf H⊖): Enthalpy change when 1 mole of a compound is formed from its elements in their most stable reference states.
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Full NotesKey Concepts
In thermodynamicsInternal energy is the sumWork (w) in chemistry primarily refersEnthalpy H = U + pVCalorimetry measures heat changes
Frequently Asked Questions
What are the important topics in Thermodynamics for Punjab Board Class 11 Chemistry?
Key topics in Thermodynamics include Basic Thermodynamic Terms: System, Surroundings, and Types of Systems, Internal Energy, Work, Heat, and the First Law of Thermodynamics, Enthalpy (H), Heat Capacity, and Relationship Between ΔH and ΔU, Enthalpy Changes: Standard Enthalpy, Formation, Combustion, Hess's Law. Study these first, then practise questions on each for Class 11 exams.
How should I revise Thermodynamics for Class 11 exams?
Learn the core ideas first, then work through the 45 practice questions on Thermodynamics. Revise definitions regularly and use flashcards for quick recall before the exam.
Sources & Official References
Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.
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