Mixtures

29 Grade 7 Integrated Science questions on Mixtures, with worked marking schemes. 29 questions are available on this topic in full.

1. Question 1

   1 mark

   Muddy water from a river is passed through a filter paper in a funnel. The clear liquid that passes through and is collected is correctly called the:

   A. Residue

   B. Filtrate

   C. Solute

   D. Solvent

   (1 mark)

   Marking scheme for this question

   Create a free account to see it

2. Question 2

   4 marks

   Differentiate between a homogeneous mixture and a heterogeneous mixture. Give one example of each.

   (4 marks)

   Marking scheme for this question

   Create a free account to see it

3. Question 3

   4 marks

   (a) Define the term mixture. (1 mark)

   (b) Name the method you would use to separate each of the following mixtures:

   (i) Sand and water (1 mark)

   (ii) Salt and water (1 mark)

   (iii) Iron filings and sulphur powder (1 mark)

   (4 marks)

   Marking scheme

   (a) A mixture is a substance made up of two or more components/substances that are physically combined and can be separated by physical means. (1 mark) (b) (i) Filtration (or decantation). (1 mark) (ii) Evaporation (or distillation if the water is also needed). (1 mark) (iii) Using a magnet (magnetic separation), since iron is magnetic and sulphur is not. (1 mark)

4. Question 4

   4 marks

   (a) Define the term mixture. (1 mark)

   (b) Name the method you would use to separate each of the following mixtures:

   (i) sand and water; (ii) common salt dissolved in water; (iii) iron filings and sand. (3 marks)

   (4 marks)

   Marking scheme

   (a) A mixture is a substance made up of two or more substances that are physically combined and not chemically joined, so each keeps its own properties and they can be separated by physical means. (1 mark) (b) (i) Filtration; (ii) evaporation (or crystallisation); (iii) using a magnet (magnetic separation). (3 marks)

5. Question 5

   1 mark

   Oil floats on water because oil

   A. is more dense than water

   B. dissolves in water

   C. is less dense than water

   D. is lighter in colour

   (1 mark)

   Marking scheme for this question

   Create a free account to see it

6. Question 6

   6 marks

   A learner is given a mixture of common salt, sand and iron filings. Describe how the learner can separate the three components to obtain each one in a pure form.

   (6 marks)

   Marking scheme

   Use a magnet to attract and remove the iron filings from the mixture (2). Add water to the remaining sand-salt mixture and stir so that the salt dissolves; filter the mixture so sand remains as residue on the filter paper and is dried (2). Heat/evaporate the filtrate (salt solution) to remove water and obtain solid salt crystals (2). Total 6 marks.

7. Question 7

   4 marks

   During distillation of salt water, water changes state twice as it is separated from the salt.

   (a) Name the two processes (state changes) that the water undergoes during distillation.

   (b) Explain why the salt is left behind in the flask.

   (4 marks)

   Marking scheme

   (a) Evaporation/boiling (liquid to gas) then condensation (gas back to liquid) (2 marks). (b) Salt has a much higher boiling point / is non-volatile, so it does not evaporate with the water; only the water vapour rises and condenses, leaving the salt behind in the flask (2 marks).

8. Question 8

   4 marks

   A learner mixed iron filings with sulphur powder.

   (a) Explain why this is described as a mixture and not a compound. (2 marks)

   (b) Describe how the learner can separate the iron filings from the sulphur. (2 marks)

   (4 marks)

   Marking scheme

   (a) It is a mixture because the iron filings and sulphur are combined physically without forming a new substance, they keep their own properties, and they can be separated by physical means (no chemical reaction has occurred / they are not combined in a fixed ratio). (2 marks) (b) Use a magnet: when a magnet is passed over (or brought near) the mixture, the iron filings are attracted to the magnet and are pulled away, leaving the sulphur behind. (2 marks)

9. Question 9

   1 mark

   Wanjiru mixes sand and common salt in a cup. She wants to separate them to recover clean salt. Which combination of methods should she use, in the correct order?

   A. Dissolve in water, filter, then evaporate the filtrate

   B. Evaporate first, then add more sand

   C. Use a magnet to remove the salt

   D. Filter first, then dissolve the residue

   (1 mark)

   Marking scheme for this question

   Create a free account to see it

10. Question 10

    1 mark

    Iron filings can be separated from a mixture of iron filings and sulphur using

    A. distillation

    B. filtration

    C. evaporation

    D. a magnet

    (1 mark)

    Marking scheme for this question

    Create a free account to see it

11. Question 11

    1 mark

    After leaving muddy water undisturbed for some time, the soil settles at the bottom and the clear water is gently poured off into another container without disturbing the sediment. This process is called:

    A. Evaporation

    B. Decantation

    C. Condensation

    D. Filtration

    (1 mark)

    Marking scheme for this question

    Create a free account to see it

12. Question 12

    1 mark

    A mixture is different from a compound because in a mixture the substances:

    A. Are not chemically combined and keep their own properties

    B. Cannot be separated by physical means

    C. Always form a new substance with new properties

    D. Are chemically combined in a fixed ratio

    (1 mark)

    Marking scheme for this question

    Create a free account to see it

13. Question 13

    2 marks

    State two ways in which the ability to separate mixtures is useful in everyday life in Kenya.

    (2 marks)

    Marking scheme

    Any two, 1 mark each: purifying/treating drinking water (filtration/distillation); separating maize/beans from chaff during harvesting (winnowing/sieving); obtaining salt from seawater/lakes by evaporation; recovering valuable materials in industry/mining; separating milk cream/butter; recycling scrap metals using magnets.

14. Question 14

    3 marks

    Describe how you would separate a mixture of sand and salt. Outline the steps clearly.

    (3 marks)

    Marking scheme for this question

    Create a free account to see it

15. Question 15

    1 mark

    Filtration is used to separate

    A. two miscible liquids

    B. two gases

    C. an insoluble solid from a liquid

    D. a soluble solid from a liquid

    (1 mark)

    Marking scheme for this question

    Create a free account to see it

16. Question 16

    1 mark

    In a salt solution, salt dissolves completely in water. In this solution, the salt is the __ and the water is the __.

    A. Suspension; colloid

    B. Solute; solvent

    C. Solvent; solute

    D. Residue; filtrate

    (1 mark)

    Marking scheme for this question

    Create a free account to see it

17. Question 17

    1 mark

    When black ink is spotted on filter paper and one end is dipped in water, the ink separates into different coloured bands. This separation technique is known as:

    A. Distillation

    B. Sublimation

    C. Chromatography

    D. Sieving

    (1 mark)

    Marking scheme for this question

    Create a free account to see it

18. Question 18

    4 marks

    Filtration is a common method of separating mixtures in the laboratory.

    (a) State the type of mixture that can be separated by filtration.

    (b) Distinguish between the terms 'residue' and 'filtrate'.

    (4 marks)

    Marking scheme for this question

    Create a free account to see it

19. Question 19

    4 marks

    A learner is given a mixture of sand, common salt and iron filings.

    (a) Name the method that can be used to separate the iron filings from the mixture. (1 mark)

    (b) Describe how the salt can be separated from the sand after the iron filings have been removed. (3 marks)

    (4 marks)

    Marking scheme

    (a) Using a magnet (magnetic separation), since iron is attracted to a magnet while sand and salt are not. (1 mark) (b) Add water to the remaining mixture and stir so that the salt dissolves but the sand does not. Filter the mixture to remove the sand, which remains as residue on the filter paper, leaving salt solution (filtrate). Heat/evaporate the salt solution so that the water evaporates, leaving solid salt crystals behind. (3 marks)

20. Question 20

    1 mark

    A mixture is a combination of two or more substances that

    A. always form a solution

    B. cannot be separated

    C. are not chemically combined

    D. form a new substance

    (1 mark)

    Marking scheme for this question

    Create a free account to see it

21. Question 21

    1 mark

    Which one of the following is an example of a mixture found in the home?

    A. Milk

    B. Oxygen gas

    C. Distilled water

    D. Pure copper wire

    (1 mark)

    Marking scheme for this question

    Create a free account to see it

22. Question 22

    1 mark

    Which of the following methods would you use to obtain pure water from salty water?

    A. Filtration

    B. Using a magnet

    C. Distillation

    D. Decanting

    (1 mark)

    Marking scheme for this question

    Create a free account to see it

23. Question 23

    3 marks

    A mixture is heated in a flask. The vapour passes through a condenser cooled by running water, and the liquid that forms is collected in a beaker.

    (a) Identify the method of separation described above. (1 mark)

    (b) Name two mixtures that can be separated using this method. (2 marks)

    Marking scheme for this question

    Create a free account to see it

24. Question 24

    1 mark

    A pupil wants to obtain pure water from salty seawater so that the water can be reused. Which separation method is MOST appropriate?

    A. Winnowing

    B. Simple distillation

    C. Filtration

    D. Sieving

    (1 mark)

    Marking scheme for this question

    Create a free account to see it

25. Question 25

    1 mark

    A garage mechanic wants to separate iron filings that have accidentally mixed with sawdust. The most suitable method of separation is:

    A. Distillation

    B. Filtration

    C. Using a magnet

    D. Evaporation

    (1 mark)

    Marking scheme for this question

    Create a free account to see it

26. Question 26

    1 mark

    Distillation is used to separate a mixture of

    A. salt and pepper

    B. iron and sulphur

    C. two miscible liquids with different boiling points

    D. sand and water

    (1 mark)

    Marking scheme for this question

    Create a free account to see it

27. Question 27

    1 mark

    A farmer separates maize grains from the lighter chaff by pouring them slowly from a height on a windy day so the wind blows the chaff away. This method of separating a mixture is called:

    A. Filtration

    B. Winnowing

    C. Chromatography

    D. Decantation

    (1 mark)

    Marking scheme for this question

    Create a free account to see it

28. Question 28

    1 mark

    The method used to separate a mixture of salt and water is

    A. filtration

    B. decanting

    C. magnetism

    D. evaporation

    (1 mark)

    Marking scheme for this question

    Create a free account to see it

29. Question 29

    1 mark

    Which of the following is an example of a homogeneous mixture?

    A. Oil and water

    B. Salt solution

    C. Sand and water

    D. Iron filings and sand

    (1 mark)

    Marking scheme for this question

    Create a free account to see it

30. 22 more marking schemes are on this page. A free account opens all of them, and lets you build your own paper on the topics you have actually taught, laid out in KNEC format with its full marking scheme.

    Create a free account

More Grade 7 Integrated Science topics