Thermal Physics B lecture notes

Dunman High School (Senior High Physics Department) 9646 Physics Topic 6B: Thermal Physics (II) 6B-1 H2 Topic 6B Thermal Physics (II)

Dunman High School (Senior High Physics Department) 9646 Physics Topic 6B: Thermal Physics (II) 6B-2 Content  Kinetic Theory of Matter  Internal Energy  Ideal Gases and the Ideal Gas Law  Internal Energy of an Ideal Gas  The First Law of Thermodynamics  P-V Diagrams Learning Outcomes Candidates should be able to (a) show an understanding that internal energy is determined by the state of the system and that it can be expressed as the sum of a random distribution of kinetic and potential energies associated with the molecules of a system. (b) relate a rise in temperature of a body to an increase in its internal energy. (c) explain using a simple kinetic model for matter why i. melting and boiling take place without a change in temperature, ii. the specific latent heat of vaporisation is higher than specific latent heat of fusion for the same substance, iii. cooling effect accompanies evaporation. (d) recall and use the first law of thermodynamics expressed in terms of the change in internal energy, the heating of the system and the work done on the system. (e) recall and use the ideal gas equation pV = nRT, where n is the amount of gas in moles. (f) show an understanding of the significance of the Avogadro constant as the number of atoms in 0.012 kg of carbon-12.

Dunman High School (Senior High Physics Department) 9646 Physics Topic 6B: Thermal Physics (II) 6B-3 (g) use molar quantities where one mole of any substance is the amount containing a number of particles equal to the Avogadro constant. (h) recall and apply the relationship that the mean kinetic energy of a molecule of an ideal gas is proportional to the thermodynamic temperature to new situations or to solve related problems.

Dunman High School (Senior High Physics Department) 9646 Physics Topic 6B: Thermal Physics (II) 6B-4 INTRODUCTION Now that we have dealt with how we perceive heat and thermal energy at a macroscopic level, let us deal with how heat manifests at a microscopic level. In this set of lecture n otes, we’ll be dealing with the kinetic theory of matter, and thermodynamics. 6.3 KINETIC THEORY 6.3.1 The Kinetic Model of Matter Learning Outcome (a) show an understanding that internal energy is determined by the state of the system and that it can be expressed as the sum of a random distribution of kinetic and potential energies associated with the molecules of a system. The kinetic model of matter refers to the theory that attempts to explain the macroscopic behaviour of matter in terms of their microscopic properties. Key to this model is the simple assumption that all matter is made of atoms/molecules. Any atom in a substance possesses two different kinds of energies, that being kinetic, and potential energy. Random kinetic energy refe