Pearson Edexcel IGCSE Physics · Year 10–11
Specification points 5.1, 5.3–5.7 and 5.15–5.22. Density, pressure, $p=h\rho g$, kinetic theory and the two gas laws. Physics-only points 5.2P and 5.8P–5.14P (specific heat capacity and changes of state) are not taught here.
From your teacher
Almost every lost mark on Topic 5 is a unit, not a formula. Convert $\text{cm}^3$ to $\text{m}^3$ by dividing by $10^6$ before you write $\rho=m/V$. Convert °C to kelvin before you write $p_1/T_1=p_2/T_2$. Use $g=10\,\text{N/kg}$ unless the paper gives another value. I will keep stopping you from leaving $h\rho g$ as the total pressure when the question has asked you to include the atmosphere.
| Word | What I award |
|---|---|
| State | A short fact. No working. “Absolute zero is $-273^\circ\text{C}$.” |
| Calculate | Equation, substitution, answer with unit. Convert first. |
| Describe | What you do, in order. Density practicals live here. |
| Explain | A cause-and-effect chain. Gas pressure answers must mention collisions. |
| Suggest | A sensible improvement or reason. Repeats, meniscus, sinker, no air bubbles. |
Lesson A · 5.1, 5.3–5.4
Units and conversions, $\rho=m/V$, regular solid, liquid, eureka can, core practical 5.4.
Lesson B · 5.5–5.7
$p=F/A$, fluids act in all directions, $p=h\rho g$, when to add the atmosphere.
Lesson C · 5.15–5.22
Collisions, absolute zero, Kelvin, $T\propto$ average KE, Boyle and $p/T$.
Eight calculations and explains marked the way I mark — convert, equation, substitute, unit.
| Point | You must be able to | Lesson |
|---|---|---|
| 5.1 | Use °C, K, J, kg, kg/m³, m, m², m³, m/s, m/s², N, Pa. Convert g, cm³, cm², g/cm³ | A |
| 5.3 | Use $\rho = m/V$ and recall typical units kg/m³ | A |
| 5.4 | Practical: density of a regular solid, an irregular solid (eureka can) and a liquid | A |
| 5.5 | Use $p=F/A$. Pa $= \text{N/m}^2$ | B |
| 5.6 | Recall that the pressure in a fluid at rest acts equally in all directions | B |
| 5.7 | Use $p=h\rho g$ for a pressure difference. Add atmospheric pressure when asked for the total | B |
| 5.15 | Explain gas pressure using random motion and collisions with the walls | C |
| 5.16–5.17 | Absolute zero $-273^\circ\text{C}$; $T(\text{K})=\theta(^\circ\text{C})+273$ | C |
| 5.18–5.19 | Higher $T$ → greater average molecular speed; Kelvin $T$ is proportional to average KE | C |
| 5.20 | Qualitative: smaller $V$ (same $T$) → more frequent collisions → $p$ up; higher $T$ (same $V$) → faster / harder collisions → $p$ up | C |
| 5.21–5.22 | $p_1/T_1=p_2/T_2$ at constant $V$; $p_1V_1=p_2V_2$ at constant $T$. Fixed mass. Kelvin only in $p/T$ | C |
Not on this Double Award site
5.2P and 5.8P–5.14P are Physics-only: specific heat capacity ($J/\text{kg}\,^\circ\text{C}$), changes of state, and temperature–time graphs. Do not revise melting or boiling curves here. Particles appear only as far as you need them for gas pressure.