Chapter 4 Practice Paper: Separation Techniques — mark scheme (print)

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QQ/S1SCI/CH4

Secondary 1 · Lower Secondary Science (G2 / G3)

Mark scheme

Separation Techniques

Chapter 4 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	AThe solid held back is the residue. The liquid that drips through is the filtrate.	1
2	CDistillation evaporates the solvent and then condenses it. Evaporation alone loses the solvent.	1
3	BDifferent dyes travel different distances up the paper.	1
4	DNot every metal is magnetic. Aluminium is not picked up by a magnet.	1
5	AEvaporation leaves the dissolved solid behind.	1
6	CThe liquid that passes through is the filtrate. The bits held on the cloth are the residue.	1
7	DFilter paper holds back undissolved solids. Dissolved substances go through with the water.	1
8	BThe vapour cools and condenses. The liquid collected is the distillate.	1
9	APen ink dissolves in the solvent and adds its own colours. A pencil mark stays put.	1
10	CThe solvent evaporates and is condensed. Dissolved salts are left in the flask.	1

Section B: Structured questions[20 marks]

Question	Answer and marking points	Marks
1(a)	Filter the mixture. The gravel is the residue. Rinse it and leave it to dry. Filter [1] Gravel is the residue, then dry it [1]	2
1(b)	Evaporate that liquid. The water leaves and sugar crystals remain. Evaporate the liquid that passed through [1] Sugar crystals remain [1]	2
1(c)	Evaporation loses the water to the air. Distillation cools the vapour so the water can be collected. Evaporation loses the water [1] Distillation condenses and collects the water [1]	2
	Total for Question 1	6
2(a)	Pencil does not dissolve. Pen ink would add extra colours and spoil the comparison. Pencil does not dissolve / pen ink would add extra spots [1]	1
2(b)	Below the spot, so the spot is not washed off into the solvent. Below the ink spot [1]	1
2(c)	The ink is a mixture of at least two dyes. They travel different distances. The ink is a mixture / contains more than one dye [1] The dyes travel different distances [1]	2
2(d)	The note was likely written with pen 2, or with an ink of the same dyes. The note ink matches pen 2 / the same dyes [1]	1
	Total for Question 2	5
3(a)	Use a magnet. Magnet / magnetic attraction [1]	1
3(b)	Aluminium is not magnetic. A magnet only picks up magnetic materials such as iron. Aluminium is not magnetic [1] A magnet separates magnetic materials only [1]	2
3(c)	Dissolved salt passes through the filter paper with the water. Filtration removes undissolved solids only. Dissolved salt passes through [1] Filtration removes undissolved solids only [1]	2
	Total for Question 3	5
4(a)	Any one: there is little land to collect rain; demand is high; sea water is salty. A valid reason, such as limited catchment or high demand [1]	1
4(b)	Distillation [1] Accept reverse osmosis as the idea that dissolved salts are held back.	1
4(c)	Any two: turn off a dripping tap; take a shorter shower; do not leave the tap running while washing. First valid way [1] Second valid way [1]	2
	Total for Question 4	4

— End of mark scheme —