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Thermal Physics - Objectives

Content

• Internal energy is the sum of the randomly distributed kinetic energies and potential energies of the particles in a body.
• The internal energy of a system is increased when energy is transferred to it by heating or when work is done on it (and vice versa), e.g. a qualitative treatment of the first law of thermodynamics.
• Appreciation that during a change of state the potential energies of the particle ensemble are changing but not the kinetic energies. Calculations involving transfer of energy.
• For a change of temperature: Q = mc ∆ θ where c is specific heat capacity.
• Calculations including continuous flow.
• For a change of state Q = ml where l is the specific latent heat.
• Gas laws as experimental relationships between p, V, T and the mass of the gas.
• Concept of absolute zero of temperature.
• Ideal gas equation: pV = nRT for n moles and pV = NkT for N molecules.
• Work done = p∆V
• Avogadro constant N A, molar gas constant R, Boltzmann constant k
• Molar mass and molecular mass.
• Brownian motion as evidence for existence of atoms.
• Explanation of relationships between p, V and T in terms of a simple molecular model.
• Students should understand that the gas laws are empirical in nature whereas the kinetic theory model arises from theory.
• Assumptions leading to pV = 1/3Nm (c_rms)²  including derivation of the equation and calculations.
• A simple algebraic approach involving conservation of momentum is required.
• Appreciation that for an ideal gas internal energy is kinetic energy of the atoms.
• Use of average molecular kinetic energy = 1/2m (c_rms)² = 3/2 kT = 3RT/2N_A
• Appreciation of how knowledge and understanding of the behaviour of a gas has changed over time.

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