#isothermal

Heat Transfer Work Distinction and Internal Energy Change

Which of the following statements is incorrect about isothermal processes?

**Heat and work distinction** heat is energy transfer due to temperature difference, random molecular motion, work is organized energy transfer due to macroscopic force, e.g., piston movement, both path functions depend on process, not state, internal energy U state function depends only on state (T for ideal gas), ΔU path independent, Q and W path dependent but Q-W = ΔU path independent. For an ideal gas in an isothermal process ( T = constant ), Δ U = 0 , and heat balances work. Option B is incorrect; internal energy does not increase. Using first law ΔU = Q - W, W = ∫ P

Ref: NCERT > Physics Book > Thermodynamics > Heat Transfer Work Distinction and Internal Energy Change

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Heat Transfer Work Distinction and Internal Energy Change

In an isothermal process for an ideal gas, what happens to the internal energy?

**Heat and work distinction** heat is energy transfer due to temperature difference, random molecular motion, work is organized energy transfer due to macroscopic force, e.g., piston movement, both path functions depend on process, not state, internal energy U state function depends only on state (T for ideal gas), ΔU path independent, Q and W path dependent but Q-W = ΔU path independent. For an ideal gas, internal energy ( U ) depends only on temperature. In an isothermal process, temperature remains constant ( Δ T = 0 ), so Δ U = 0 . Using first law ΔU = Q - W, W = ∫

Ref: NCERT > Physics Book > Thermodynamics > Heat Transfer Work Distinction and Internal Energy Change

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Heat Transfer Work Distinction and Internal Energy Change

Which thermodynamic process involves a constant temperature?

**Internal energy change** ΔU = Q - W, for same initial and final states ΔU same regardless of path, but Q and W differ, e.g., isothermal expansion from V₁ to V₂ ΔU=0 Q=W=n R T ln(V₂/V₁), adiabatic expansion between same volumes ΔU=-W, Q=0, different Q,W same ΔU if same T change, illustrating state vs path functions. An isothermal process is characterized by constant temperature ( T = constant ). For an ideal gas, this implies P V = constant , with heat exchange balancing work done. Using first law ΔU = Q - W, W = ∫ P dV, isobaric W = P ΔV, isothermal

Ref: NCERT > Physics Book > Thermodynamics > Heat Transfer Work Distinction and Internal Energy Change

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First Law of Thermodynamics Applications

Which of the following statements is correct about an isothermal process for an ideal gas?

**Internal energy** state function depends only on temperature for ideal gas, U = f/2 n R T, change ΔU = n C_v ΔT, first law connects heat, work, internal energy, for expansion work done by gas positive, compression work done on gas negative, heat added positive. In an isothermal process ( T = constant ), the internal energy of an ideal gas ( U , temperature-dependent) remains constant ( Δ U = 0 ), and heat supplied equals work done ( Δ Q = Δ W ), making option C correct. Using first law ΔU = Q - W, W = ∫ P dV, isobaric

Ref: NCERT > Physics Book > Thermodynamics > First Law of Thermodynamics Applications

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CHEMISTRY

What is the entropy change when two gases mix isothermally?

Mixing of gases increases disorder due to increased randomness, so Δ S > 0. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Some Basic Concepts, Structure of Atom and Periodicity, Topic: Mole concept, atomic models and periodic trends.

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Thermodynamics

Which thermodynamic process occurs at constant temperature?

Isothermal is the scientifically accurate answer to this question. Within the study of Thermodynamics, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of Isothermal directly address what is being asked. Among the other options, Isochoric, Adiabatic, and Isobaric do not correctly answer this question because they either refer to different concepts, describe properties of other molecules or processes, or represent common misconceptions about this topic.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 1

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