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Introduction to Chemistry

28 Grade 10 Chemistry questions on Introduction to Chemistry, with worked marking schemes. 28 questions are available on this topic in full.

  1. Question 1

    1 mark

    The purpose of a fume chamber in a chemistry laboratory is to:

    A. Store volatile chemicals at a low temperature

    B. Keep clean apparatus free from dust

    C. Allow experiments that give off poisonous gases to be done while the gases are drawn away

    D. Dry wet apparatus quickly after washing

    (1 mark)

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  2. Question 2

    1 mark

    Every bottle of chemicals kept in the school laboratory must carry a clear label mainly because:

    A. The label shows how much of the chemical is left in the bottle

    B. A wrong chemical may otherwise be used, causing a dangerous reaction or injury

    C. The shelves of the store are then easier to arrange in alphabetical order

    D. The label prevents the chemical from evaporating through the stopper

    (1 mark)

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  3. Question 3

    4 marks

    Suggest two ways in which chemistry contributes to the conservation of the environment. Explain each.

    (4 marks)

    Marking scheme

    Award 1 mark for each way named and 1 mark for its explanation, to a maximum of 4. Accept any two pairs: - Treatment of industrial effluent ✓1 — chemical treatment removes acids and heavy metals before waste water from factories is released into rivers such as the Nairobi River, protecting aquatic life ✓1 - Recycling of plastics and metals ✓1 — chemical processes allow used materials to be reprocessed, reducing litter and the demand for new raw materials ✓1 - Monitoring of air and water pollution ✓1 — chemical analysis detects harmful gases and dissolved substances so that pollution can be controlled early ✓1 - Development of cleaner fuels and biodegradable materials ✓1 — these release fewer harmful gases or break down naturally, reducing long-term pollution ✓1 A named way with no explanation scores 1.

  4. Question 4

    1 mark

    A learner pours out more sodium chloride than is needed for an experiment. The reason the excess should not be returned to the stock bottle is that:

    A. The stock bottle may overflow and spill onto the bench

    B. The chemical loses its strength once it has been exposed to air

    C. The returned portion may be contaminated and spoil the whole stock

    D. It wastes the time of the class using the laboratory next

    (1 mark)

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  5. Question 5

    2 marks

    Explain why a Bunsen burner should be left burning with a yellow (luminous) flame when it is not being used for heating.

    (2 marks)

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  6. Question 6

    3 marks

    During a practical lesson, a learner accidentally spills concentrated sodium hydroxide solution on the laboratory bench. Describe the steps the learner should take.

    (3 marks)

    Marking scheme

    Award 1 mark per correct step, to a maximum of 3: - Inform the teacher/laboratory technician immediately and keep other learners away from the spill ✓1 - Wear gloves (or use a suitable protective means) and dilute the spill with plenty of water, or soak it up with dry sand or a mop as directed ✓1 - Wipe the bench clean, rinse it with plenty of water and wash the hands thoroughly afterwards ✓1 Accept "neutralise with a weak acid such as dilute ethanoic acid as directed by the teacher" in place of the dilution step.

  7. Question 7

    1 mark

    The extraction and processing of soda ash at Lake Magadi is an example of the application of chemistry in the:

    A. Pharmaceutical manufacturing industry

    B. Textile dyeing industry

    C. Food preservation industry

    D. Mining and mineral extraction industry

    (1 mark)

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  8. Question 8

    1 mark

    Which procedure for lighting a Bunsen burner is correct?

    A. Close the air hole, light the gas at the mouth of the barrel, then open the air hole as required

    B. Connect the rubber tubing, open the air hole and turn on the gas while looking for a match

    C. Turn on the gas tap and allow gas to flow for some time before striking a match

    D. Open the air hole fully, turn on the gas tap, then bring a lit splint to the barrel

    (1 mark)

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  9. Question 9

    1 mark

    Chemistry is best described as the study of:

    A. The composition, structure and properties of matter and the changes matter undergoes

    B. Rocks, soils and the internal structure of the earth

    C. The living organisms found in an ecosystem and their life processes

    D. Forces, motion and the different forms of energy in nature

    (1 mark)

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  10. Question 10

    2 marks

    Distinguish between organic chemistry and inorganic chemistry.

    (2 marks)

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  11. Question 11

    3 marks

    State the use of each of the following safety items found in a chemistry laboratory: (a) fire blanket; (b) bucket of dry sand; (c) first aid kit.

    (3 marks)

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  12. Question 12

    1 mark

    A Grade 10 class is required to transfer exactly 25.0 cm³ of a solution into a conical flask. The most suitable apparatus for this transfer is a:

    A. Measuring cylinder

    B. Boiling tube

    C. Pipette

    D. Graduated beaker

    (1 mark)

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  13. Question 13

    3 marks

    Explain three ways in which chemistry is applied in agriculture in Kenya.

    (3 marks)

    Marking scheme

    Award 1 mark for each way correctly explained, to a maximum of 3. Accept any three of: - Manufacture and correct use of fertilisers to supply nutrients such as nitrogen and phosphorus to crops like maize and tea ✓1 - Testing soil pH and adding lime to correct acidic soils so that crops grow better ✓1 - Manufacture and safe use of pesticides, acaricides and herbicides to control pests, ticks and weeds ✓1 - Formulation of animal feed supplements and veterinary medicines for dairy cattle and poultry ✓1 - Food preservation and processing, e.g. chemicals used in preserving milk or in processing sugar ✓1 A bare mention such as "fertilisers" without saying what they do scores 0.

  14. Question 14

    4 marks

    State four career opportunities in Kenya for which a good background in chemistry is required.

    (4 marks)

    Marking scheme

    Award 1 mark for each correct career, to a maximum of 4. Accept any four of: - Medical doctor, clinical officer or nurse ✓ - Pharmacist or pharmaceutical technologist in a drug manufacturing plant ✓ - Agricultural officer, soil scientist or agronomist ✓ - Chemical/process engineer in an industry such as cement, sugar or fertiliser manufacture ✓ - Food scientist or quality-control analyst in a dairy or brewery ✓ - Forensic analyst in a government laboratory ✓ - Teacher or lecturer of chemistry ✓ - Petroleum or mining geologist, water quality analyst, environmental officer ✓ Reject vague answers such as "scientist" or "working in a laboratory" (0).

  15. Question 15

    1 mark

    The flame that should be used when heating a solution with a Bunsen burner is the:

    A. Yellow luminous flame, because it spreads over a wider area of the container

    B. Blue non-luminous flame, because the gas burns completely and produces more heat

    C. Yellow luminous flame, because it is brighter and easier to see

    D. Blue non-luminous flame, because it deposits soot which holds in the heat

    (1 mark)

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  16. Question 16

    1 mark

    A gas is produced in a test tube during a practical lesson. The safe way to find out how the gas smells is to:

    A. Use the hand to waft a small amount of the gas towards the nose

    B. Heat the mixture more strongly so that the smell becomes clear

    C. Place the nose at the mouth of the test tube and breathe in deeply

    D. Pour a little of the gas into the palm and smell it

    (1 mark)

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  17. Question 17

    4 marks

    Describe how a small amount of liquid should be heated safely in a test tube.

    (4 marks)

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  18. Question 18

    3 marks

    Suggest how each of the following should be disposed of after a practical lesson: (a) pieces of a broken test tube; (b) unused concentrated acid; (c) a solid residue containing a lead compound.

    (3 marks)

    Marking scheme

    Award 1 mark for each acceptable method: - (a) Swept up with a brush and dustpan (never with bare hands) and placed in the labelled broken-glass bin ✓1 - (b) Added slowly to a large volume of water to dilute it and then washed down the sink with plenty of running water, or stored in the labelled acid waste container, as directed by the teacher ✓1 - (c) Placed in the labelled heavy-metal/chemical waste container for special disposal; it must not be poured down the sink or thrown into the school compound ✓1 Reject "throw it in the dustbin" for (a) or (c) (0).

  19. Question 19

    1 mark

    Learners are not allowed to eat or drink in the chemistry laboratory mainly because:

    A. Food crumbs make the laboratory untidy

    B. Harmful chemicals may get onto the food and be swallowed

    C. Food attracts insects and rodents into the laboratory

    D. The smell of food interferes with the smell of gases produced

    (1 mark)

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  20. Question 20

    6 marks

    State three laboratory rules that must be observed during a chemistry practical lesson. In each case, give a reason for the rule.

    (6 marks)

    Marking scheme

    Award 1 mark for each rule and 1 mark for its matching reason, to a maximum of 6 (3 rules + 3 reasons). Accept any three pairs: - Do not carry out any experiment that has not been authorised by the teacher ✓1 — unknown mixtures may react violently, explode or release poisonous gases ✓1 - Report every accident, breakage or spillage to the teacher at once ✓1 — so that first aid or a clean-up can be given before the injury or damage becomes serious ✓1 - Wash hands with soap and water at the end of every practical ✓1 — to remove chemical residues that could later be swallowed or cause skin irritation ✓1 - Keep the working bench free of bags, books and unnecessary apparatus ✓1 — to prevent apparatus being knocked over and to leave a clear path in an emergency ✓1 - Never work alone in the laboratory ✓1 — there would be nobody to help or call for help in case of an accident ✓1 A rule without a reason scores 1 only.

  21. Question 21

    4 marks

    State the meaning of each of the following hazard warning labels and give one example of a substance that carries it: (a) oxidising; (b) toxic.

    (4 marks)

    Marking scheme

    Award 1 mark for each meaning and 1 mark for each valid example: - (a) Oxidising: the substance supplies oxygen and therefore makes other substances burn more fiercely, even without a flame ✓1; example: potassium manganate(VII), hydrogen peroxide, potassium nitrate ✓1 - (b) Toxic: the substance is poisonous and can cause serious injury or death if swallowed, inhaled or absorbed through the skin ✓1; example: lead(II) nitrate, mercury, chlorine gas ✓1 An example that does not match the stated meaning scores 0 for that example.

  22. Question 22

    1 mark

    A stock bottle of concentrated hydrochloric acid in the school laboratory should carry the hazard warning label:

    A. Corrosive

    B. Oxidising

    C. Flammable

    D. Explosive

    (1 mark)

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  23. Question 23

    1 mark

    While pouring dilute sulphuric acid, a learner splashes some of it on the back of the hand. The correct first action is to:

    A. Wash the area with plenty of running water, then report to the teacher

    B. Apply cooking oil on the area to seal the skin

    C. Pour dilute sodium hydroxide solution on the area to neutralise the acid

    D. Rub the area with a dry cloth and continue with the experiment

    (1 mark)

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  24. Question 24

    3 marks

    State the use of each of the following apparatus in the chemistry laboratory: (a) wire gauze; (b) tripod stand; (c) spatula.

    (3 marks)

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  25. Question 25

    2 marks

    State the meaning of the term chemistry.

    (2 marks)

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  26. Question 26

    1 mark

    A Grade 10 learner studies the structure and the properties of methane, the main compound in the biogas produced from cow dung in a family digester in Kisii. The branch of chemistry in which the learner is working is:

    A. Physical chemistry

    B. Analytical chemistry

    C. Organic chemistry

    D. Inorganic chemistry

    (1 mark)

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  27. Question 27

    1 mark

    When measuring 20 cm³ of water using a measuring cylinder, the reading is taken with the eye level with the:

    A. Bottom of the curved surface of the water

    B. Top of the curved surface of the water

    C. Any part of the scale, since the volume is the same throughout

    D. Highest point at which the water touches the glass wall

    (1 mark)

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  28. Question 28

    2 marks

    Explain why the outside of a test tube must be wiped dry before it is heated over a flame.

    (2 marks)

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