Composite Materials

15 Grade 8 Pre-Technical Studies questions on Composite Materials, with worked marking schemes. 15 questions are available on this topic in full.

1. Question 1

   1 mark

   A learner observes that reinforced concrete is strong in both compression and tension. The tension strength is mainly provided by the:

   A. Sand

   B. Cement

   C. Steel reinforcement

   D. Water

   (1 mark)

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2. Question 2

   1 mark

   A composite material is best defined as a material made by combining:

   A. Two or more different materials to get improved properties

   B. Only natural materials

   C. A single pure element

   D. Two pieces of the same metal

   (1 mark)

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3. Question 3

   6 marks

   A civil engineer chooses reinforced concrete for building a bridge. (a) State two components that make up reinforced concrete. (2 marks) (b) Explain two advantages of using composite materials over single materials. (4 marks)

   (6 marks)

   Marking scheme

   (a) Concrete (cement, sand, aggregate) and steel reinforcement bars (1 each, max 2). (b) Any two explained: high strength-to-weight ratio - strong yet light so structures are strong without being too heavy; combine properties of components - e.g. concrete resists compression while steel resists tension; corrosion/weather resistance - last longer; can be moulded into complex shapes (2 marks each explained, max 4).

4. Question 4

   1 mark

   Which of the following is a common natural composite material?

   A. Copper

   B. Wood

   C. Steel

   D. Aluminium

   (1 mark)

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5. Question 5

   1 mark

   In a composite material, the material that surrounds and holds the reinforcement together is called the:

   A. Aggregate

   B. Fibre

   C. Filler

   D. Matrix

   (1 mark)

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6. Question 6

   1 mark

   A builder reinforces concrete with steel bars to improve a structure. In this reinforced concrete composite, what role do the steel bars mainly play?

   A. They keep the concrete warm

   B. They add colour to the concrete

   C. They carry the tension (pulling) forces

   D. They make the concrete lighter

   (1 mark)

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7. Question 7

   6 marks

   A learner collects different items in the school and discovers that some are made from composite materials such as reinforced concrete and fibreglass. (a) Define a composite material. (2 marks) (b) Give two reasons why composite materials are often preferred to single materials in construction. (4 marks)

   (6 marks)

   Marking scheme

   (a) A composite material is a material made by combining two or more different materials (a matrix and a reinforcement) to produce a new material whose combined properties are better than those of the individual materials acting alone, for example concrete reinforced with steel bars, or glass fibres embedded in a resin matrix (fibreglass). (b) Two reasons composites are preferred: (i) They are stronger and able to carry greater loads than the single materials on their own (e.g. steel adds tensile strength to concrete, which is weak in tension). (ii) They combine useful properties such as light weight with high strength and resistance to corrosion or cracking, giving longer-lasting and more durable structures. (Other acceptable: cost-effective for the strength gained.)

8. Question 8

   5 marks

   (a) Define the term composite material. (2 marks) (b) Give three examples of composite materials used in Kenya and state one use of each. (3 marks)

   (5 marks)

   Marking scheme

   (a) A composite material is a material made by combining two or more materials with different properties to produce a new material with improved/better properties (2 marks). (b) Any three with a use: reinforced concrete - buildings/bridges; fibreglass - water tanks/boats/roofing; plywood - furniture/roofing; wood (natural composite) - furniture; mud and wattle - traditional walls (1 mark each correct pairing, max 3).

9. Question 9

   1 mark

   A technician explains to learners that concrete reinforced with steel bars is stronger than plain concrete because it combines two materials. What term describes a material made by combining two or more different materials to get improved properties?

   A. Recycled material

   B. Raw material

   C. Pure material

   D. Composite material

   (1 mark)

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10. Question 10

    1 mark

    Fibreglass is a composite made of glass fibres embedded in:

    A. Plastic resin

    B. Steel

    C. Clay

    D. Cement

    (1 mark)

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11. Question 11

    6 marks

    Fibreglass water tanks are common in Kenyan homes. Explain three reasons why fibreglass is a suitable material for making water tanks. (6 marks)

    (6 marks)

    Marking scheme

    Any three explained (2 marks each): it is light in weight so easy to transport and install; it is resistant to corrosion/rust so it does not contaminate the water and lasts long; it is watertight and can be moulded into shape; it is strong and durable and withstands weather. Max 6.

12. Question 12

    1 mark

    Which property makes composite materials such as fibreglass preferred for making boat hulls?

    A. They conduct electricity well

    B. They are light and resistant to corrosion

    C. They are very heavy

    D. They rust easily

    (1 mark)

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13. Question 13

    1 mark

    A learner studies a canoe made by combining glass fibre with resin and notices it is both light and strong. What is this combination of two or more materials called?

    A. A natural element

    B. A pure metal

    C. A single polymer

    D. A composite material

    (1 mark)

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14. Question 14

    1 mark

    Which of the following pairs correctly identifies the matrix and reinforcement in reinforced concrete?

    A. Matrix: sand; Reinforcement: water

    B. Matrix: concrete; Reinforcement: steel bars

    C. Matrix: cement only; Reinforcement: air

    D. Matrix: steel bars; Reinforcement: concrete

    (1 mark)

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15. Question 15

    1 mark

    Reinforced concrete used in constructing a school storey building is a composite of concrete and:

    A. Steel bars

    B. Timber

    C. Glass

    D. Rubber

    (1 mark)

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