Primary 3 Science · Answers and explanations
Textbook Challenge: All Seven Chapters
Use this page to check the worksheet together. Talk about why each answer is right. Total: 30 marks.
Section A · Multiple choice 16 marks
1. Frosted glass is used for a bathroom window. Which word describes frosted glass?1 mark
(A) Transparent(B) Translucent(C) Opaque(D) Flexible
Answer: (B) TranslucentTranslucent materials let only some light through, so objects behind look blurry. Transparent lets most light through. Opaque lets none through.
2. Glass is made by heating which natural material until it melts?1 mark
(A) Sand(B) Clay(C) Wood(D) The sap of a tree
Answer: (A) SandHot melted sand is shaped, then cools into clear glass. Clay is used for ceramic.
3. Which material is made by shaping clay and then baking it until hard?1 mark
(A) Glass(B) Rubber(C) Fabric(D) Ceramic
Answer: (D) CeramicBaking makes ceramic hard, but it can still break easily if dropped.
4. Plastic is usually made in factories using which of these?1 mark
(A) Sand(B) Clay(C) Oil from the ground(D) Cotton plants
Answer: (C) Oil from the groundPlastic and some rubber are made from oil. Plastic lasts a long time, so we should reuse and recycle it.
5. A ship is made of metal, which sinks. Why can the ship still float?1 mark
(A) Metal is lighter than water(B) There is a lot of trapped air inside it(C) Ships are very flexible(D) Metal is transparent
Answer: (B) There is a lot of trapped air inside itThe trapped air inside the ship helps it float, even though most metals sink on their own.
6. Which group of animals can keep a constant body temperature?1 mark
(A) Mammals(B) Reptiles(C) Fish(D) Amphibians
Answer: (A) MammalsMammals are warm-blooded. Reptiles, fish and amphibians have a body temperature that changes with their surroundings.
7. A starfish is not a fish. Which fact helps explain this?1 mark
(A) It lives in water(B) It has fins(C) It has feathers(D) It has no scales or gills
Answer: (D) It has no scales or gillsFish usually have scales, fins and gills. A starfish has none of these, so it is not a fish.
8. Mould, mushrooms and yeast are grouped together as which kind of living thing?1 mark
(A) Bacteria(B) Plants(C) Fungi(D) Animals
Answer: (C) FungiThey cannot make their own food and they reproduce by spores, so scientists put them in their own group, fungi.
9. Which of these is a way that useful bacteria help us?1 mark
(A) They make bread dough rise(B) They help to break down food in our bodies(C) They turn soybeans into tempeh(D) They grow into mushrooms
Answer: (B) They help to break down food in our bodiesYoghurt contains useful bacteria. Yeast (bread) and the white fungus for tempeh are fungi, not bacteria.
10. The leaves of a mimosa plant fold when they are touched. Which thing that living things can do does this show?1 mark
(A) Respond to changes(B) Reproduce(C) Grow bigger(D) Need water
Answer: (A) Respond to changesFolding the leaves is a response to being touched. It helps protect the plant.
11. How many stages are there in the life cycle of a plant such as a soybean?1 mark
(A) Two(B) Four(C) Five(D) Three
Answer: (D) ThreeThe three stages are the seed, the young plant and the adult plant.
12. A mosquito has an egg, a larva, a pupa and an adult. A frog has an egg, a tadpole and an adult. Which stage does the frog not have?1 mark
(A) Egg(B) Adult(C) Pupa(D) Tadpole
Answer: (C) PupaThe mosquito has four stages. The frog has only three, and it has no pupa stage.
13. Which action helps most to stop mosquitoes from breeding at home?1 mark
(A) Leave water in plant pot plates(B) Pour away stagnant water(C) Keep water in open pails(D) Close the windows at night
Answer: (B) Pour away stagnant waterMosquitoes lay their eggs in still water. Removing stagnant water removes their breeding spots.
14. Which pair is made only of objects that a magnet attracts?1 mark
(A) An iron nail and a steel pin(B) A plastic ruler and a rubber band(C) A copper coin and a wooden stick(D) A glass marble and an aluminium can
Answer: (A) An iron nail and a steel pinIron and steel are magnetic materials. Plastic, rubber, copper, wood, glass and aluminium are not attracted.
15. Which test is the best way to show that an object is a magnet?1 mark
(A) It attracts a steel clip(B) It is made of metal(C) It feels heavy(D) It repels another magnet
Answer: (D) It repels another magnetOnly a magnet can push another magnet away. Magnetic materials such as steel are attracted to a magnet too, so attraction alone does not prove it.
16. Which change makes an electromagnet stronger?1 mark
(A) Using fewer batteries(B) Using a plastic nail instead of an iron nail(C) Winding more turns of wire around the iron nail(D) Taking the battery away
Answer: (C) Winding more turns of wire around the iron nailMore turns of wire, or more batteries, make the electromagnet stronger so it picks up more clips.
Section B · Show what you know 14 marks
17. A glass bottle is not the best container for a young child to carry. Give a reason.2 marks
Answer: Glass is fragile, so it breaks easily when dropped and the sharp pieces could hurt the child.Glass is fragile. A plastic or metal bottle is safer because it does not shatter so easily.
18. Car tyres are made of rubber. Give two properties of rubber that make it suitable for tyres.2 marks
Answer: Rubber is strong (it can take hard knocks) and flexible (it bends and does not break on rough roads).The tyre must hold the weight of the car and absorb bumps without cracking or breaking.
19. Name the three things that all living things need.2 marks
Answer: Water, food and air.Without water, food or air, living things cannot survive. Plants make their own food using light.
20. Write one similarity and one difference between the life cycles of a frog and a mosquito.2 marks
Answer: Similarity: both start as an egg and both have a young stage that does not look like the adult. Difference: the frog has three stages but the mosquito has four (it has a pupa stage).Any correct similarity and any correct difference are accepted. Compare the number of stages and the look of the young.
21. Ali winds 10 turns of wire and uses 1 battery for one electromagnet. He winds 20 turns and uses 2 batteries for another. He says the second is stronger because it has more turns of wire. Why is his test not fair?2 marks
Answer: He changed two things at once, the number of turns and the number of batteries, so he cannot tell which one made the difference.In a fair test only one thing (the variable) is changed. Everything else stays the same.
22. Day and night happen again and again. Why do we call this a cycle, and what causes it?2 marks
Answer: It is a repeated pattern of change. It is caused by the Earth rotating once every 24 hours, so each place faces the Sun and then faces away.A cycle is a pattern that repeats. Cycles happen in living things (life cycles) and in non-living things (day and night).
23. A scientist finds a living thing growing on old bread. It does not make its own food and it reproduces by spores. Which group does it belong to? Give a reason.2 marks
Answer: Fungi. It does not make its own food and it reproduces by spores, like mould, mushrooms and yeast.Both clues match the fungi group. Plants make their own food and do not grow on bread.
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