Topic 1 Practice Paper: States of matter — mark scheme (print)

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QQ/IGCSE-CHEM/T1

IGCSE · Cambridge IGCSE Chemistry (Extended (Core + Supplement))

Mark scheme

States of matter

Topic 1 Practice Paper · Maximum mark: 30

Notes for markers

Award one mark for each point marked [1], up to the marks shown for the part.
Accept answers worded differently that show the same understanding.
Units are required where the answer line shows one. ecf: allow an error carried forward.

Section A: Multiple-choice questions[10 marks]

Question	Answer
1	ALiquid particles are close together but randomly arranged, so they can slide past one another.	1
2	DBoiling takes in energy to allow particles to escape the liquid and form a gas.	1
3	BSolid particles are held in a regular arrangement and can only vibrate about fixed positions.	1
4	BImpurities lower the melting point and make the substance melt over a range of temperatures.	1
5	AEvaporation is the loss of the fastest particles from the surface, below the boiling point.	1
6	CHeating gives the particles more kinetic energy, so their average speed increases.	1
7	BThe gas with the lowest relative molecular mass diffuses fastest, and hydrogen has the lowest Mᵣ.	1
8	Ap₁V₁ = p₂V₂ gives 150 × 400 = 100 × V₂, so V₂ = 600 cm³.	1
9	DA flat section on a cooling curve marks a change of state, which happens at a constant temperature.	1
10	CGas particles are far apart and move quickly and randomly, so they spread to fill the container.	1

Section B: Structured questions[20 marks]

Question	Answer and marking points	Marks
11(a)	Random but close together / touching. random arrangement / close together [1]	1
11(b)	Easy to compress. easy to compress / compressible [1]	1
11(c)	The particles are held in a regular arrangement and can only vibrate about fixed positions, so they cannot move to take the shape of the container. particles in fixed positions / regular arrangement [1] they cannot move past one another [1]	2
	Total for Question 11	4
12(a)	The temperature rises as the solid warms, stays constant at 80 °C while it melts, rises as the liquid warms, stays constant at 220 °C while it boils. Then all of the substance is a gas. rises, then flat at 80 °C (melting) [1] rises, then flat at 220 °C (boiling) [1] flat sections show a change of state at constant temperature [1]	3
12(b)	The energy supplied is used to overcome the forces between the particles so they can move out of their fixed positions, rather than to increase their kinetic energy. energy used to overcome forces between particles [1] so kinetic energy / temperature does not increase [1]	2
12(c)	At 220 °C the gas condenses to a liquid; at 80 °C the liquid freezes to a solid. condensing at 220 °C and freezing at 80 °C [1]	1
	Total for Question 12	6
13(a)	diffusion [1]	1
13(b)	The dye and water particles move randomly. There are more dye particles at the bottom, so on average more move away from that area than towards it, until the dye is evenly spread. particles move randomly [1] net movement from higher to lower concentration [1]	2
13(c)	Warm the water. This gives the particles more kinetic energy, so they move faster and spread more quickly. warm the water [1] particles have more energy / move faster [1]	2
	Total for Question 13	5
14(a)	120 × 250 = p₂ × 100, so p₂ = 30000 ÷ 100 = 300 kPa. correct substitution 120 × 250 = p₂ × 100 [1] 300 kPa [1]	2
14(b)	The particles are now in a smaller space, so they collide with the walls more frequently each second. More frequent collisions mean a greater force per unit area, so the pressure rises. more frequent collisions with the walls [1] greater force per unit area [1]	2
14(c)	The temperature (and the mass/amount of gas). [1]	1
	Total for Question 14	5

— End of mark scheme —