5.1 Thermal Physics
5.1.1 Temperature
(a) thermal equilibrium
(b) absolute scale of temperature (i.e. the thermodynamic scale) that does not depend on property of any particular substance
(c) temperature measurements both in degrees Celsius (°C) and in kelvin (K)
(d) Temperature in K = temperature in °C + 273
5.1.2 Solid, liquid and gas
Learners should be able to demonstrate and apply their knowledge and understanding of:
(a) solids, liquids and gases in terms of the spacing, ordering and motion of atoms or molecules
(b) simple kinetic model for solids, liquids and gases
(c) Brownian motion in terms of the kinetic model of matter and a simple demonstration using smoke particles suspended in air
(d) internal energy as the sum of the random distribution of kinetic and potential energies associated with the molecules of a system
(e) absolute zero (0 K) as the lowest limit for temperature; the temperature at which a substance has minimum internal energy
(f) increase in the internal energy of a body as its temperature rises
(g) changes in the internal energy of a substance during change of phase; constant temperature during change of phase.
5.1.3 Thermal properties of materials
Learners should be able to demonstrate and apply their knowledge and understanding of:
(a) specific heat capacity of a substance; the equation
Estimating specific heat capacity, using method of mixture.
(b) (i) an electrical experiment to determine the specific heat capacity of a metal or a liquid
(ii) techniques and procedures used for an electrical method to determine the specific heat capacity of a metal block and a liquid
(c) specific latent heat of fusion and specific latent heat of vaporisation; E = mL
(d) (i) an electrical experiment to determine the specific latent heat of fusion and vaporisation
(ii) techniques and procedures used for an electrical method to determine the specific latent heat of a solid and a liquid.
5.1.4 Ideal gas
Learners should be able to demonstrate and apply their knowledge and understanding of:
(a) amount of substance in moles; Avogadro constant NA equals 6.02 × 1023 mol–1
(b) model of kinetic theory of gases
assumptions for the model:
- large number of molecules in random, rapid motion
- particles (atoms or molecules) occupy negligible volume compared to the volume of gas:
- all collisions are perfectly elastic:
- the time of the collisions is negligible compared to the time between collisions
- negligible forces between particles except during collision
(c) pressure in terms of this model. Explanation of pressure in terms of Newtonian theory.
(d) (i) the equation of state of an ideal gas pV = nRT, where n is the number of moles
(ii) techniques and procedures used to investigate PV = constant (Boyle’s law) and P/T=constant
(iii) an estimation of absolute zero using variation of gas temperature with pressure
(e) the equation , where N is the number of particles (atoms or molecules) and c2 is the mean square speed
Derivation of this equation is not required.
Note this statement. You do not need to know the long derivation that starts with the molecules in the box.
(f) root mean square (r.m.s.) speed; mean square speed Learners should know about the general characteristics of the Maxwell-Boltzmann distribution.
You don't really need to understand much about r.m.s. speed other than it is sort of an average speed of the molecules.
(g) the Boltzmann constant;
(h
You don't need to long proof with the box and the molecules. However, yo need to be able to combine the two equations and come up with the E=3/2 kT one.
(i) internal energy of an ideal gas.
Because of the assumptions made about an ideal gas, namely that there are no forces between the molecules, none of the internal energy of an ideal gas is potential energy. So, all the internal energy is made up of the kinetic energy of the particles of the gas.
Now you need to do questions. Lots of them. They are all the same, so the more you do, the less likely you are to be surprised in the exam.