Entropy and Its Changes
Understand entropy as a measure of disorder, how it changes in physical and chemical processes, and its calculation in various scenarios including phase transitions and isothermal processes.
Why this shows up in the exam
Entropy is central to predicting spontaneity and is a frequent topic in both NEET and JEE.
How NEET tests this
Practise it
These are real questions from past NEET papers that test this exact idea.
For a sample of perfect gas when its pressure changed isothermally from p₁ to pₓ the entro change is given by
Push further
More challenging44 harder questions built from the past papers above — a step up in difficulty, with distractors designed so you can't get there by elimination. Written and checked by our reviewers, not from a real paper.
Consider the complete combustion of methane: CH4(g) + 2O2(g) → CO2(g) + 2H2O(g). What are the expected signs for the enthalpy change (DeltaH), entropy change (DeltaS), and Gibbs free energy change (DeltaG) for this reaction under standard conditions?
More from Thermodynamics
Thermodynamic Processes and P-V Diagrams
Study different thermodynamic processes (isothermal, isobaric, isochoric, adiabatic, polytropic, cyclic), their definitions, characteristics, and graphical representation on P-V diagrams.
Laws of Thermodynamics
Understand the zeroth and first laws of thermodynamics, including their statements, implications, and applications to physical systems.
Internal Energy, Heat, and Work
Explore the concepts of internal energy, heat, and work, including their definitions, relationships, and how they change during various thermodynamic processes.
Ideal Gas Law and Equation
Learn the ideal gas equation, its relation to physical quantities like pressure, volume, temperature, and density, and its use in describing the behavior of ideal gases.
Gibbs Free Energy and Spontaneity
Learn how Gibbs free energy determines spontaneity, how to calculate it, and its dependence on temperature, pressure, and other thermodynamic parameters.
Enthalpy Changes and Bond Energies
Learn to calculate enthalpy changes for reactions using bond enthalpies, enthalpy of formation, and Hess's law.