Edexcel IGCSE Physics 5 Solids, liquids & gases Question Bank

- particles with larger spaces between them

Marking guidance:
- Maximum spacing should be similar to the spacing in the solid diagram.

particles slide / move / flow past each other

Ignore:
- more freely

Any three from:
- particles are far apart / much further apart
- particles move with much higher speed / have higher kinetic energy
- particles move more randomly

Accept:
- KE for kinetic energy

idea that (large number of) molecules moving randomly;

idea of equal rate of collisions in each direction;

allow atoms or particles for 'molecules'

can be acquired from diagram by showing arrows of different lengths (by eye) or different directions (by eye)

condone idea of equal number in each direction

Marking points:
- evaluation of new volume
- substitution into $p_{1}V_{1}=p_{2}V_{2}$
- rearrangement
- evaluation of new pressure

Example:
$$V_{2}=130\times\frac{5.0}{8.4}=77\ \mathrm{cm^{3}}$$$$100\times130=p_{2}\times77$$$$p_{2}=\frac{100\times130}{77}$$$$p_{2}=170\ \mathrm{kPa}$$

Accept:
- $V_{2}=77.38\ldots\ \mathrm{cm^{3}}$
- any value that rounds to $170\ \mathrm{kPa}$
- ECF different yet incorrect volume

Marking guidance:
- Deduct 1 mark for a power-of-ten error.

Any four from:
- measure mass
- use a mass balance
- measure diameter
- use ruler / callipers / micrometer
- further experimental detail, e.g. use set square against ruler, use callipers in different orientations, fully submerged, avoid splashing
- repeat readings and take average
- use formula to find volume of a sphere, e.g.
$$V=\frac{4}{3}\pi r^{3}$$
- use
$$\text{density}=\frac{\text{mass}}{\text{volume}}$$

Accept:
- scales for balance
- displacement method and measuring cylinder for measuring volume

Condone:
- letting the ice melt

Reject:
- scale for balance

- substitution into density = mass / volume
- evaluation
- unit: g/cm^3

Example:
- density = 0.94 / 1.1
- density = 0.8545...
- density = 0.85 g/cm^3

Accept:
- 0.854 or 0.855
- unit matching calculation if mass converted into kg
- standard symbols, e.g. D = M / V or rho for density

Marking guidance:
- Unit is independently marked.
- Deduct 1 mark for power-of-ten error.