Creative Science P3 & 4 Book 1 Detailed Explanations

Transcription

1 Revision Paper 1 Section A The correct answer is (2).The doll can walk (move) and says Hello when you touch one of its buttons (respond to changes). Thus options (A) and (C) are correct. The animals are grouped according to whether they give birth to their young alive or lay eggs. Animal Y is grouped together with cat, dog and dolphin and they all give birth to their young. The correct answer is (2) as the rest of the animals lay eggs. The correct answer is (1). The young of the frog is a tadpole, the young of the moth is a caterpillar and the young of a housefly is a maggot. All of them do not look like the adults. The correct answer is (2). The table is a non-living thing while the rabbit is a living thing. The correct answer is (2). Animal X is an insect that does not lay eggs in water and has 4 stages in its life cycle. (1) is incorrect as it is not an insect. (3) is incorrect as it lays eggs in water. (4) is incorrect as it has 3 stages in its life cycle. Although onion and potato are commonly grown from plant parts, they can be grown from seeds as well. Thus (4) is the correct answer. The correct answer is (4). The metal spoon sinks in water. The silk blouse and the piece of paper are not waterproof. The correct answer is (3). The balloon and the rubber band are made form rubber only. The plastic cup is made from plastic only. The pair of spectacles is made of plastic/metal and glass/ plastic. The correct answer is (2). Benches and chairs have to be made of a strong material as people sit on them. Thus wood is a suitable material as it is strong. Wood is neither soft nor flexible. It is also not waterproof. In fact, wooden benches and chairs are usually painted to make them waterproof. 10. The correct answer is (4). The only group of animals that feed their young with milk is the mammals. 11. The correct answer is (2). (1) is incorrect as the seagull is a bird so it has feathers. (3) is incorrect as the swordtail is a fish so it has scales and the seal is a mammal so it has hairs. (4) is incorrect as the catfish is a fish so it does not have hairs. 12. The correct answer is (3). Not all living things give birth to their young. Some living things lay eggs. 13. The correct answer is (1). The sparrow is a bird thus it lays eggs, has feathers, has two legs and does not feed the young with milk. The platypus is a mammal that lays eggs, feed its young with milk, has hairs and has four legs. 1

2 14. The correct answer is (3). Fabric and paper are soft. Metal and stone are hard and strong. 15. The correct answer is (2). Wool comes from sheep so it does not come from plants. The other options are correct: cotton comes from the cotton plant, silk comes from silkworms and leather comes from the hides of animals. 16. The correct answer is (4). One of the conditions needed for mould to grow is moisture. Both the bathroom and the bedroom have water vapour in their surroundings. However, the amount of water vapour in the bathroom is more than the amount of water vapour in the bedroom. Thus mould would grow faster on Bread X than on Bread Y. 17. The correct answer is (3). The guppy is a fish. The killer whale and the flying squirrel are mammals. All of them give birth to their young. The clownfish is a fish, the sparrow is a bird and the spiny anteater is a mammal and all of them lay eggs. They are grouped according to the way they reproduce. 18. The correct answer is (3). Iron and sand come from the ground. Rubber and wood come from trees. 19. The correct answer is (2). Moth has a 4-stage life cycle. The sheep and platypus are both mammals and both of them have only 4 legs, not 6 legs. 20. The correct answer is (3). A gas is a matter thus it expands when heated. It does not have a definite shape so it will take the shape of the container it is in and it does not have a definite volume and thus it can be compressed. 21. The correct answer is (2). Steam is a gas. A gas is a matter that does not have a definite shape and does not have a definite volume. 22. The correct answer is (4). (A) is correct as not all fishes lay eggs. (B) is correct. (C) is correct as some fishes like the catfish and sharks do not have scales. (D) is correct. 23. The correct answer is (1). When the seeds were given 25 ml of fertiliser, they only grew to a height of 8 cm which is 9 cm shorter than when they were given 20 ml of fertiliser. 24. The correct answer is (4). All the four statements show that living things can respond to changes around them. 25. The correct answer is (2). The readings on the weighing scale remained at 210 g. This shows that mass of the air in the jar remained the same. The plastic wrap was pushed upwards after the jar was heated and this shows that volume of the air in the jar has increased. 26. The correct answer is (3). When the frozen block melts, the amount of liquid in the glass increases thus the water level would rise, the block would become smaller and the liquid in the glass would turn red. However, the total mass of the contents in the glass remains the same. 2

3 27. The correct answer is (1). Organism X is a fungus as it cannot make its own food and reproduces from spores. It is also inedible. Garlic and staghorn fern are both plants. Jew s ears is a fungus but it is edible. 28. The correct answer is (4). Coin, sand, steam and mist are things that were never alive so (1) and (2) are incorrect. In addition, sound and heat are not matter. Coin and sand are solids so they have definite shapes and volumes while steam and mist do not have definite shapes. 29. Very little can be poured into the bottle through the funnel because the air in the bottle occupies space and it is not able to leave the bottle. So the answer is (3). 30. The correct answer is (4). To conduct the experiment, Sunny can only change one variable, which is the brand of the bread. The rest of the variables should be the same. Section B 31. (a) Some fungi, like yeast, are useful to us as they are needed in bread making. (b) Yeast is not a plant so it cannot make its own food. (c) Mushroom is a type of fungi and it cannot make its own food so it has to get its nutrients from other organisms like the rotten logs. (d) Moulds thrive in dark and damp places. 32. Glass is fragile and it may injure the baby when it breaks. In addition, glass is heavy. On the other hand, plastic is light and does not break easily. Thus it will not injure the baby. 33. (a) Material A is the hardest as it has the most number of ticks. (b) Material C. (c) A fishing line must be strong and flexible and material C is strong and highly flexible. 34. (a) Part A is the seat and it should be made of a material that is flexible and durable. Plastic, rubber or leather can be used. Part B is the wheel and it must be made of a material that is flexible so rubber should be used. Part C is the frame of the bicycle and it must be strong so metal should be used. (b) Wood is not flexible so it cannot be used to make part B. 35. Lion is a mammal that gives birth and lives on land so it should be placed in B. Ant is an insect that lays eggs and does not have wings so it should be placed in C. Dolphin is a mammal that gives birth and lives in water so it should be placed in A. Ostrich is a bird that lays eggs and has wings so it should be placed in D. 36. (a) Object A is made of metal as metal sinks in water. (b) The other object is not made of metal as it floats on water. (c) Wood and plastic are materials that float on water. Thus Object B could be made of wood or plastic. 3

4 37. Silk is a natural material that comes from silkworm and is soft so it should be placed in B. Wood is a natural material that comes from plants so it should be placed in E. Iron is a natural material that comes from the ground and is not fragile so it should be placed in C. Glass is made from a material that comes from the ground and is fragile so it should be placed in D. Nylon is a man-made material so it should be placed in A. Leather is a natural material that comes from animals and it is tough and durable so it should be placed in F. 38. Dolphin is a mammal. Ostrich is a bird. Swordtail is a fish. Grasshopper is an insect. 39. (a) In order to obtain a reliable result, the experiment needs to be conducted three times. (b) Both the yeast and bacteria cannot be seen by the naked eyes but can be seen under the microscope. Thus the similarity between them is that they are microorganisms. 40. (a) Animals which lay many eggs at a time usually do not take care of their young as they do not have the time and resources to take care of all of them. (b) From the table we can see that as the number of eggs laid by the female increase, the amount of care given by the parents decrease. (c) As the cod and the common tree frog do not take care of their young, the eggs have a higher chance of being eaten by other animals. Thus they have to lay many eggs to ensure that some of the eggs would hatch and the young will eventually grow into adults. This is to ensure that their kind will not become extinct. 41. (a) Stage X is the seed. The seed will germinate to become a seedling if the conditions are favourable. (b) The conditions needed to germination are water, warmth and oxygen. 42. (a) The rat in Container B will survive longer. (b) Since Container B is bigger than Container A, it contains more air/oxygen than Container A so the rat will be able to survive more as it has more air/oxygen. 43. (a) Carbon dioxide is a gas and smoke is made up of gases and small particles. They are both matter because they have mass and take up space. Music and heat are non-matter because they do not have mass and do not take up space. (b) A shadow is a non-matter as it does not have mass and does not take up space. 44. (a) Leftover food will decompose if they are not removed. There will be bacteria and the existence of these bacteria may affect the health of the organisms living in the insectarium. (b) Plants make food and produce oxygen which is needed by the organisms to survive. 45. (a) The bat, seal and platypus are all mammals while the emu, penguin and mynah are all birds. Thus (i) is mammals and (ii) is birds. (b) The bat is the only known mammal that can fly and the mynah is a bird that can fly as well. The emu and the penguin are birds that cannot fly. The seal and the platypus also cannot fly. Thus (i) is Can fly and (ii) is Cannot fly. 4

5 46. Cockroaches prefer a dark environment. When the light in a dark room is switched on, the environment in the room changes and the cockroaches hide themselves in a dark corner. This shows that cockroaches can respond to changes around them. Revision Paper 2 Section A The correct answer is (2). All insects have three body segments and six legs. In order to find out if an animal is an insect, we look at these two characteristics. The correct answer is (4). The mushroom is a fungus. It cannot make its own food so it needs to get nutrients from other sources (rotting logs). It reproduces from spores and does not produce flowers. The bird s nest fern is a non-flowering plant. It can make its own food and reproduces from spores. The correct answer is (1). Plastic is a man-made material that is produced from chemicals obtained from petroleum. Silver and diamond come from the ground and wool comes from sheep. The correct answer is (2). The conditions needed for germination are water, air (oxygen) and warmth (right temperature). The seeds in Pot B will not germinate as they do not have air and warmth. The seeds in Pot C will not germinate as they do not have water. The seeds in both pots A and D have water, air and warmth so they will germinate. (1) is incorrect as copper wire is made of metal. (2) is incorrect as copper wire is not soft. (4) is incorrect as the nylon bag and copper wire are not weak. (3) is correct as iron, nickel and steel are metals that are magnetic. Nylon, plastic and copper are non-magnetic materials. The correct answer is (1). Hairstyles, handwriting and the way people talk can be changed according to the environment. Everyone has unique fingerprints (No two persons have the same fingerprint) so the best way to identify a person is by looking at the fingerprints. (1) is incorrect because the toadstool is a living thing and the magazine is a non-living thing that was once alive as it is made from paper. (2) is incorrect because book is a non-living thing that was once alive as it is made from paper. (3) is incorrect as beef is a non-living thing that was once alive. (4) is correct because the wooden chair is a non-living thing that was once alive as it is made from wood, the computer is a non-living thing that was never alive and the grasshopper is a living thing. The correct answer is (2). The cockroach in Set-up B will die after some time because the mushroom is a fungus so it cannot make food and cannot replenish oxygen in the air-tight container. The cockroach in Set-up C will die after some time because the artificial plant cannot make food and cannot replenish oxygen in the air-tight container. The cockroaches in set-ups A and D will still be alive because the green plant and the cactus can make food and will replenish oxygen in the air-tight containers. In Set-up A, the green plant takes in carbon dioxide to make food in the presence of light. 5

6 9. The correct answer is (4). Both plants were placed in soil and in the same location. The only difference between the two plants is that Plant A was given water but Plant B was not. From here, we can conclude that plants need water to stay alive. 10. The correct answer is (1). All living things need air, food and water. They can grow and reproduce, will die eventually and can respond to changes around them. 11. The correct answer is (4). Both the water lotus and the morning glory are living things so they need air and water. They are plants so they need sunlight to make food. The morning glory also has a very weak stem. 12. The correct answer is (3). A seed will germinate if the conditions are correct. The roots will grow first. The shoot will appear after the roots and then the young plant will eventually grow into an adult plant. 13. The correct answer is (4). (1) is incorrect as mosquitoes lay their eggs in stagnant water, not necessarily pond water. (2) is incorrect as the larva and the pupa both breathe through breathing tubes. (3) is incorrect as the young larva and pupa are also considered as a mosquito. The pupa breathes through breathing tube while the adult mosquito breathes through spiracles. 14. The correct answer is (2). In order to conduct a fair experiment, only one variable can be changed while the rest of the variables must remain unchanged. To find out whether plants need light to grow, Jane should use jugs W and Z as the only difference between these two jugs is the location. To find out whether plants need oxygen to grow, she should use jugs W and X as the only difference between the two jugs is that Jug W has oxygen while Jug X does not have oxygen. 15. ( 1) is incorrect as Jasline only has one uncle and one aunt. (2) is incorrect as Jasline s grandfather only has two siblings. (3) is incorrect as the family tree shows four generations. (4) is the answer as the symbol representing Jasline is connected to the square which represents Jasline s father and the family tree shows her father s family. 16. The correct answer is (2). A sponge is a solid. It has many air spaces which contain air and air can be compressed. That is why a sponge can be squeezed. Heat is a non-matter as it does not have mass and does not occupy space. Sugar is solid so it has a definite shape and cannot be compressed. 17. The correct answer is (4). The mosquito pupa and the wriggler breathe through breathing tubes. The crab and the mudskipper breathe through gills. The butterfly and the grasshopper breathe through spiracles. The frog and the earthworm breathe through skin. 18. The correct answer is (3). The bird s nest fern is a non-flowering plant so it reproduces from spores. The hibiscus plant bears flowers so it reproduces from seeds. 6

7 19. The correct answer is (1). To answer this question, we need to look at the characteristics of animals. Animals can move freely by themselves and can reproduce. Non-living things like animal waste or chemicals can also help to fertilise the soil. Similarly, non-living things are also not affected by diseases. 20. The correct answer is (1). Toadstools are fungi so they cannot make their own food and need to get nutrients from other sources. The tree trunks provide the toadstools with nutrients that they need to survive. 21. The correct answer is (4). In September, the death rate of the guppies was higher than the birth rate so the number of guppies in September actually decreased. Thus the graph should be sloping downwards instead of upwards. 22. The correct answer is (3). Animals move away from their habitats when their living conditions become unfavourable. Floods, droughts and presence of disease-carrying flies are all unfavourable conditions that may cause the population of the animals to decrease. 23. The correct answer is (3) A, B and C only. Animals Characteristics They are birds. They: lay eggs Chicken have two legs Duck have outer coverings of feathers omnivorous They are mammals. They: give birth to their young Zebra have four legs Deer have outer coverings of hair herbivorous Tree snake Great white shark The tree snake and Great white shark are similar in some ways. For example, both of them have no legs, an outer body covering of scales and are carnivores. However, the tree snake lays eggs but the Great white shark does not. 24. The correct answer is (2). (1) is incorrect. The young of the parrot resembles its parents while the young of the toad does not. (3) is incorrect. The young of the guppy resembles its parents. (4) is incorrect. The butterfly has a 4-stage life cycle. 25. The correct answer is (2). To conduct a fair test, John can only change the amount of Chemical Y given while the number of stalks of flowers and the amount of water given must be kept the same. 26. The correct answer is (3). The population of Species C has been decreasing steadily from 1955 to The correct answer is (4). P has a definite volume and a definite shape so it must be a solid. Q has a definite volume but no definite shape so it must be a liquid. R does not have a definite 7

8 shape and does not have a definite volume so it must be a gas. 28. The correct answer is (2). Mary should only change the type of soil used and keep the number of bean seeds and the location of the experiment the same. 29. The correct answer is (4). X has definite volume and definite shape so it must be a solid. Y does not have definite volume and does not have definite shape so it must be a gas. Z does not have definite shape but has definite volume so it must be a liquid. 30. The correct answer is (3). All birds are warm-blooded and have feathers. Not all birds can fly. Some examples of birds that cannot fly are penguin, ostrich and emu. Section B 31. (a) Don inherited both his features from his father. May inherited her round face from her mother and her sharp nose from her father. Jack inherited his flat nose from his mother. Sam inherited his square face from his father and his flat nose from his mother. May and Sam inherited one feature from each parent. (b) We can inherit our features from our parents as well as our grandparents so Jack may have inherited his angular face from his grandparents. 32. (a) Material D. (b) To make a raincoat, the materials used must be waterproof so that the person wearing it will not get wet. It must be light so that it can be carried around easily. It must also be flexible so that it will be comfortable to wear and it must be strong so that it does not break easily. 33. (a) Curve Y. The yolk provides the developing embryo with nutrients as it grows. As the developing embryo gets the nutrients from the yolk, the mass of the yolk will decrease. (b) As the embryo gets bigger and increases in mass over time, the mass of the yolk will decrease as it is used up by the embryo. 34. The function of the control set-up is to compare the results obtained. To draw the control set-up, we need to know what Tom is trying to find out from the experiment. Tom wants to find out if plants take in water. Thus we should draw an identical set-up without the plant so that we will know that the loss of water in the actual set-up is due to the plant taking in water through the roots. 35. Child A inherited single eyelids from the parents. Child B inherited single eyelids and hitchhiker s thumb from the parents. Child C inherited single eyelids, hitchhiker s thumb and attached earlobes from the parents. All three children inherited single eyelids from their parents. 8

9 36. To find out if overcrowding affects the growth of plants, Susan can only change the number of plants in the pots. The types of plants used and the type of soil used should be the same. 37. Rubber does not break when hit and can be stretched so it should be placed in (c). Porcelain breaks when hit and does not allow light to pass through so it should be placed in (b). Glass breaks when hit and allows light to pass through so it should be placed in (a). Wood does not break when hit and cannot be stretched so it should be placed in (d). 38. (a) Both animals have wings. (b) Animal A has two legs while Animal B has six legs. 39. (a) The living plant contains chlorophyll which is able to trap light energy to make food. Thus photosynthesis is taking place in the living plant in Jar X. (b) The plant in Jar X is able to photosynthesise to provide the grasshopper with oxygen while the leaves in Jar Y is not able to photosynthesise to provide the grasshopper with oxygen. Thus Grasshopper A will survive longer than grasshopper B as the oxygen in Jar X is replenished by the plant. 40. (a) Flask B was left under the sun and the plant in Flask B lost more water to the surroundings compared to the plant in Flask A as its surrounding temperature was higher. Therefore it took in more water than the plant in Flask A. Thus line X represents the change in volume of water in Flask B. (b) The stopper is used to prevent the water in the flasks from evaporating. 41. (a) Substance X starts to melt at 17 ºC so the highest temperature for it to exist as a solid is 17 ºC. (b) Substance Y starts to melt at 27 ºC so the lowest temperature for it to exist as a liquid is 27 ºC. 42. The chicken has a 3-stage life cycle while the butterfly has a 4-stage life cycle. The young of the chicken looks like the adult but the young of the butterfly does not look like the adult. 43. (a) True. Substance Y is a matter so it occupies space. (b) Not possible to tell. From the classification table, we only know that Substance Y is a non-solid so it can be a liquid which has a definite volume. (c) False. Substance Y is a non-solid so it does not have a definite shape. (d) False. Substance Y is a matter so it has mass. 44. Group A is wrongly grouped. Both the frog and the eagle are animal-eaters. 45. The wooden ruler and the ice cubes will float on water while the metal key and the glass marble will sink in water. 46. Plants need light energy to make food. Plant E was placed in a glass box. Glass is transparent and allows light to pass through so Plant E can make food and grow well. Plant F was placed in a cardboard box. Cardboard is opaque and does not allow light to pass through so Plant F cannot make food and it will not grow well. 9