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#temperature dependence

14 public questions tagged with this topic.

Partial Pressures and Gas Mixtures

The rms speed of a gas molecule is 400 m/s at 200 K. What is the rms speed at 800 K?

**Gas mixtures** ideal gas law applies to each component, P_total = Σ n_i R T/V, partial pressure P_i = n_i R T/V, mole tion X_i = n_i/n_total, P_i = X_i P_total, enabling calculation of individual pressures from composition, important for kinetic theory and chemistry. v_rms ∝ √(T), (v₂)/(v₁) = √((T₂)/(T₁)).(v₂)/(400) = √((800)/(200)) = √(4) = 2.v₂ = 400 × 2 = 800 m/s. Substituting values gives 800 m/s, which matches expected kinetic theory result, confirming mean free path λ = 1/(√2 n π d²), ideal gas law P V = n R T and v_rms = √(3 R T/M) relations.

Ref: NCERT > Physics Book > Behaviour of Perfect Gas and Kinetic Theory > Partial Pressures and Gas Mixtures

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Surface Tension, Capillarity and Excess Pressure

Why does the viscosity of liquids generally decrease with increasing temperature?

Higher temperatures increase molecular kinetic energy in liquids, weakening intermolecular forces, reducing resistance to flow, and thus lowering viscosity, as noted in the chapter. As per NCERT, applying relevant law/formula with correct units and sign convention leads to Intermolecular forces weaken. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.

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Surface Tension, Capillarity and Excess Pressure

Why does a liquid’s surface tension decrease with increasing temperature?

Increasing temperature weakens cohesive forces between liquid molecules by increasing their kinetic energy, reducing the contractile force at the surface, thus lowering surface tension, as noted in the chapter. As per NCERT, applying relevant law/formula with correct units and sign convention leads to Cohesive forces weaken. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.

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