Classes of Fire

31 Grade 8 Integrated Science questions on Classes of Fire, with worked marking schemes. 31 questions are available on this topic in full.

1. Question 1

   1 mark

   Which of the following fires is classified as Class A?

   A. Burning wooden furniture and paper

   B. Fire in a live electrical socket

   C. Burning magnesium metal

   D. Burning petrol in a jerrican

   (1 mark)

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2. Question 2

   1 mark

   Which method of extinguishing a fire works by removing the heat from the fire triangle?

   A. Turning off the fuel supply valve

   B. Covering the flames with a fire blanket

   C. Sprinkling dry powder over the flames

   D. Cooling the burning material with water

   (1 mark)

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3. Question 3

   3 marks

   (a) Name the class of fire that involves flammable liquids such as petrol and paraffin. (1 mark)

   (b) State why water should NOT be used to put out an electrical fire. (2 marks)

   (3 marks)

   Marking scheme

   (a) Class B fire. (b) Water should not be used on an electrical fire because water is a good conductor of electricity, so it can conduct the current to the person fighting the fire and cause an electric shock (electrocution); it may also worsen the situation rather than extinguish it.

4. Question 4

   1 mark

   A fire caused by burning wood and paper is classified as

   A. Class A

   B. Class C

   C. Class B

   D. Class D

   (1 mark)

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5. Question 5

   1 mark

   Water should NOT be used to extinguish a fire caused by

   A. electrical equipment

   B. burning cloth

   C. burning wood

   D. burning paper

   (1 mark)

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6. Question 6

   1 mark

   During a fire drill, learners are taught that a carbon dioxide extinguisher works mainly by:

   A. Raising the temperature of the burning material

   B. Cutting off the supply of oxygen to the fire

   C. Supplying extra oxygen to the flames

   D. Adding more fuel to slow the burning

   (1 mark)

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7. Question 7

   4 marks

   Fires are classified according to the type of material burning.

   State the class of fire and give one example of a burning material for each of the following:

   (i) burning kerosene (paraffin) (2 marks)

   (ii) burning electrical wiring (2 marks)

   (4 marks)

   Marking scheme

   (i) Class B; example - kerosene/paraffin/petrol/oil/any flammable liquid (class 1 mark, example 1 mark). (ii) Class C; example - live electrical wiring/switched-on appliance/electrical socket (class 1 mark, example 1 mark). Total 4 marks.

8. Question 8

   1 mark

   A fire involving burning magnesium ribbon in a laboratory belongs to which class of fire?

   A. Class D

   B. Class B

   C. Class C

   D. Class A

   (1 mark)

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9. Question 9

   1 mark

   A fire breaks out in a kitchen when a pan of cooking oil overheats and ignites. Under which class of fire does this incident fall?

   A. Class D

   B. Class A

   C. Class B

   D. Class C

   (1 mark)

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10. Question 10

    1 mark

    Which extinguishing agent is MOST suitable for putting out a Class A fire involving wood and paper?

    A. Water

    B. Carbon dioxide gas

    C. Dry sand only

    D. Foam designed for oils

    (1 mark)

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11. Question 11

    1 mark

    A fire involving live electrical equipment is classified as

    A. Class A

    B. Class D

    C. Electrical fire

    D. Class B

    (1 mark)

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12. Question 12

    1 mark

    The fire triangle shows that fire can be extinguished by

    A. removing any one of the three elements

    B. raising the temperature

    C. increasing oxygen supply

    D. adding more fuel

    (1 mark)

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13. Question 13

    1 mark

    Which class of fire involves flammable liquids such as petrol and paraffin?

    A. Class C

    B. Class D

    C. Class A

    D. Class B

    (1 mark)

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14. Question 14

    3 marks

    Draw and label the fire triangle.

    (3 marks)

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15. Question 15

    4 marks

    Explain how EACH of the following methods can be used to put out a fire, linking each to the fire triangle:

    (a) Using a fire blanket. (2 marks)

    (b) Turning off a leaking gas cylinder valve. (2 marks)

    (4 marks)

    Marking scheme

    (a) A fire blanket smothers the flames by cutting off the oxygen supply (removes oxygen from the triangle) - 2 marks. (b) Closing the valve stops the flow of gas, removing the fuel from the triangle so the fire cannot continue - 2 marks.

16. Question 16

    1 mark

    A small pan of oil catches fire on a jiko. The MOST appropriate way to put it out is to:

    A. Fan the flames to blow them out

    B. Cover the pan with a damp cloth or lid to cut off air

    C. Throw a cup of water into the hot oil

    D. Carry the burning pan outside quickly

    (1 mark)

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17. Question 17

    3 marks

    A fire starts in a school laboratory when a bottle of ethanol spills onto a hot bench and ignites, spreading to nearby wooden stools.

    (a) Identify the class of fire caused by the burning ethanol. (1 mark)

    (b) Identify the class of fire caused by the burning wooden stools. (1 mark)

    (c) State one suitable extinguishing agent for the wooden stools. (1 mark)

    (3 marks)

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18. Question 18

    3 marks

    A carbon dioxide (CO2) fire extinguisher is available in a computer laboratory.

    (a) Explain why CO2 is preferred over water for extinguishing fires involving computers and other electrical equipment. (2 marks)

    (b) State how CO2 extinguishes the fire. (1 mark)

    (3 marks)

    Marking scheme

    (a) Water conducts electricity and can cause electric shock / damage the electrical equipment, whereas CO2 does not conduct electricity and leaves no residue (2 marks). (b) CO2 cuts off/displaces the supply of oxygen to the fire (smothers it) - 1 mark.

19. Question 19

    1 mark

    Class C fires are caused by

    A. ordinary combustibles

    B. electrical equipment

    C. cooking oils

    D. flammable gases

    (1 mark)

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20. Question 20

    3 marks

    During a fire safety lesson, learners discuss different classes of fire.

    (a) Name the class of fire caused by burning flammable liquids such as petrol and kerosene. (1 mark)

    (b) State why water should NOT be used to put out a fire caused by burning cooking oil. (2 marks)

    (3 marks)

    Marking scheme

    (a) Class B fire. (1 mark) (b) Water is denser than the burning oil, so it sinks below the oil and comes into contact with the very hot surface. The water turns rapidly into steam, which expands violently and splatters/throws the burning oil out of the container, spreading the flames and making the fire larger/worse rather than putting it out. (2 marks)

21. Question 21

    5 marks

    A fire broke out in a school laboratory when a bottle of ethanol spilled near a Bunsen burner.

    (a) Identify the class of this fire. (1 mark)

    (b) State the appropriate method to extinguish this fire. (2 marks)

    (c) Explain why water should not be used. (2 marks)

    Marking scheme

    (a)

    Class B fire (flammable liquid — ethanol).

    (b)

    Use a carbon dioxide (CO₂) fire extinguisher or a dry chemical powder extinguisher.

    Do NOT use water as it can spread the burning liquid.

    (c)

    Water is denser than ethanol, so the burning liquid would float on water and spread the fire further.

22. Question 22

    1 mark

    A learner notices sparks and flames coming from a switched-on television set. This is an example of which class of fire?

    A. Class D

    B. Class B

    C. Class C

    D. Class A

    (1 mark)

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23. Question 23

    1 mark

    The three things that must be present for a fire to burn, often shown as the fire triangle, are:

    A. Fuel, heat and oxygen

    B. Oxygen, water and ash

    C. Water, fuel and smoke

    D. Heat, smoke and carbon dioxide

    (1 mark)

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24. Question 24

    3 marks

    A market has stalls selling firewood and charcoal (Class A), a fuel station selling petrol (Class B), and a section with electrical connections (Class C).

    (a) State one suitable extinguishing agent for the Class A section. (1 mark)

    (b) Explain why the SAME agent named in (a) should NOT be used at the petrol section. (2 marks)

    (3 marks)

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25. Question 25

    1 mark

    One way to put out a fire is to remove one element of the fire triangle. Covering a fire with a blanket removes

    A. heat

    B. fuel

    C. oxygen

    D. water

    (1 mark)

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26. Question 26

    1 mark

    Why is water NOT recommended for extinguishing a fire caused by burning petrol?

    A. Water immediately cools petrol into a solid

    B. Petrol floats on water and the fire spreads

    C. Water reacts with petrol to form oxygen

    D. Petrol dissolves completely in water

    (1 mark)

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27. Question 27

    1 mark

    For fire to start and continue burning, it requires

    A. heat, water and fuel

    B. fuel, water and oxygen

    C. oxygen, water and heat

    D. fuel, heat and oxygen

    (1 mark)

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28. Question 28

    4 marks

    (a) Name the class of fire that involves burning of cooking oils and fats in a kitchen. (1 mark)

    (b) State the most suitable method of putting out a fire caused by burning electrical equipment, and give a reason why water should NOT be used. (3 marks)

    (4 marks)

    Marking scheme

    (a) Class F fire (fire involving cooking oils and fats). (b) The most suitable method is to use a carbon dioxide (CO2) fire extinguisher (or a dry powder extinguisher) which smothers/cuts off the oxygen supply. Water should not be used because water is a good conductor of electricity, so it can cause electric shock to the person fighting the fire (and can spread the fire).

29. Question 29

    3 marks

    (a) Name the class of fire that involves flammable liquids such as petrol and kerosene. (1 mark)

    (b) State two reasons why water should NOT be used to put out a fire caused by burning cooking oil in the kitchen. (2 marks)

    (3 marks)

    Marking scheme

    (a) Class B fire (fires involving flammable liquids). (b) Any two of the following: - Water is denser than oil, so it sinks below the burning oil instead of smothering it. - The hot oil turns the water into steam violently, causing the burning oil to splash and spread the fire. - It can spread the burning oil over a larger area, increasing the danger of the fire.

30. Question 30

    5 marks

    The fire triangle shows the three requirements for a fire to continue burning.

    (a) Name the three components of the fire triangle. (3 marks)

    (b) Using the fire triangle, explain how covering a burning oil pan with a lid puts out the fire. (2 marks)

    (5 marks)

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31. Question 31

    1 mark

    Which of the following is the safest first action when an electrical appliance catches fire at home?

    A. Pour water directly onto the appliance

    B. Blow air onto the flames to cool them

    C. Switch off the mains power supply

    D. Spray perfume near the flames

    (1 mark)

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