Question 1

All plants ____.

Accepted Answer

A. make their own food. All plants make their own food through photosynthesis. Not all plants reproduce by seeds (e.g. ferns reproduce by spores), not all bear flowers and fruits (e.g. mosses, ferns), and plants need oxygen for respiration both day and night.

Question 2

Many years ago, a scientist discovered an animal P and studied its characteristics. Some of the characteristics of animal P are as follows: A lays egg; B has four legs; C can swim in water; D can produce milk to feed the young. Which of the above characteristics made it difficult to classify animal P as a mammal?

Accepted Answer

A. A only. Mammals do not typically lay eggs — they give birth to live young. So characteristic A (lays egg) makes it difficult to classify P as a mammal. Characteristics B, C and D are consistent with being a mammal.

Question 3

Study the four set-ups as shown below. All set-ups were placed near a window on a sunny day. Limewater changes from colourless to chalky in the presence of carbon dioxide. In which set-up will the limewater turn chalky the slowest?

Accepted Answer

C. C. In set-up C, the fern (a green plant) is placed in sunlight and undergoes photosynthesis, absorbing carbon dioxide and releasing oxygen. This reduces the carbon dioxide passing into the limewater, so the limewater turns chalky the slowest. The beetle (A) respires producing CO2; set-up B has no living thing but air still has CO2; the mushroom (D) is non-green and only respires, releasing CO2.

Question 4

Some scientists claim that plants will glow in the dark when modified. Which part of the plant cell has been modified for the investigation?

Accepted Answer

B. B. Part B is the nucleus, which contains the genetic material (DNA). To genetically modify a plant so that it glows in the dark, the nucleus (which contains the genes) has to be modified.

Question 5

Which one of the substances is not transported by the human circulatory system?

Accepted Answer

D. undigested food. The circulatory system transports water, digested food and gases (oxygen and carbon dioxide). Undigested food is not absorbed into the blood — it remains in the digestive tract and is removed as faeces.

Question 6

The two graphs below show Mary's breathing before exercise and during exercise respectively. In which ways will Mary's breathing change during exercise? A Time taken for one breath; B Volume of oxygen breathed in; C Volume of nitrogen breathed out; D Volume of carbon dioxide breathed out

Accepted Answer

D. A, B, C and D. During exercise the breathing rate and depth both increase. Time for one breath shortens (A), volume of oxygen breathed in increases (B), volume of carbon dioxide breathed out increases (D), and since the total volume of air breathed in/out increases, the volume of nitrogen (a large fraction of air) breathed out also increases (C).

Question 7

The diagram shows part of the stem of a small tree with a ring of bark removed. Removing the ring of bark takes away the food-carrying tube but not the water-carrying tube. The effect of removing the ring of bark was observed after some time. What would be the effect?

Accepted Answer

D. Upper stem swollen, upper leaf green, lower stem normal, lower leaf green. Food (made by the upper leaves via photosynthesis) cannot pass down to the lower stem because the food-carrying tube (phloem) has been removed. Food accumulates above the ring, causing the upper stem to swell. The water-carrying tube (xylem) is intact, so water still reaches all leaves — upper and lower leaves remain green. The lower stem is normal in size as it cannot receive food but is not damaged structurally yet.

Question 8

A group of boys wanted to carry out an experiment to find out if mopping the floor will increase their pulse rate. The steps of their experiment are as follows: A Take a wet mop; B Mop the floor continuously for 10 minutes; C Stop mopping and measure the pulse rate immediately. Their teacher said that they have forgotten an important step and without that step, they cannot make a conclusion. Which step should they include in their experiment so that they can make a conclusion?

Accepted Answer

C. Measure the pulse rate at rest. To know whether mopping increases pulse rate, the boys must first measure their pulse rate at rest (before mopping) to compare with the rate after mopping. Without a baseline, no conclusion about the increase can be made.

Question 9

The diagram below shows the human reproductive systems. Where are the human reproductive cells produced?

Accepted Answer

C. A and D. In the male, sperm (reproductive cells) are produced in the testes — labelled A. In the female, eggs (reproductive cells) are produced in the ovaries — labelled D. So the reproductive cells are produced in A and D.

Question 10

The diagram shows a cross-section of a flower. Which one of the following statements is correct?

Accepted Answer

A. Fertilisation occurs at D.. D is the ovary/ovule region where fertilisation occurs after the male reproductive cell from a pollen grain joins the female reproductive cell (egg). A is the stigma (not the ovule, so it doesn't become a seed). Pollen is transferred to A (stigma), not B (anther — pollen comes from the anther). The reproductive cells (sperm) are inside pollen (from B) and the egg is in D.

Question 11

Which graph correctly shows the relationship between the mass of seed leaves and the height of the seedling?

Accepted Answer

B. Mass of seed leaves decreases as height of seedling increases (falling line). The seed leaves (cotyledons) store food for the growing seedling. As the seedling uses up the stored food to grow taller, the mass of the seed leaves decreases. Therefore as the height of the seedling increases, the mass of the seed leaves decreases.

Question 12

The diagrams below show some fruits on a tree and a baby inside a mother's womb. Alex made three statements about the fruit and the baby. A It develops into an adult. B It developed after fertilisation. C It obtains food from its parent for growth. Which of the following is correct?

Accepted Answer

C. Fruit: B,C ; Baby: A,B,C. A fruit does NOT develop into an adult — the seed inside the fruit germinates into a new plant. The fruit develops from the ovary after fertilisation (B true) and the developing seeds inside obtain food from the parent plant (C true). The baby in the womb does develop into an adult (A true), developed after fertilisation (B true), and obtains food from the mother through the placenta (C true).

Question 13

Ravi compared the life cycles of two animals and made the following statements. • Both their young resemble the adult. • Both animals have 3 stages in their life cycles. Which animals was Ravi comparing?

Accepted Answer

D. Chicken and grasshopper. A chicken has 3 stages: egg → chick → adult, and the chick resembles the adult. A grasshopper has 3 stages: egg → nymph → adult, and the nymph resembles the adult. A beetle and a butterfly each undergo complete metamorphosis with 4 stages (egg, larva, pupa, adult) and the young do not resemble the adult.

Question 14

Siti carried out an experiment on germination of seeds using two different types of seeds placed in identical containers A and B as shown below. She predicted that the seeds will germinate faster with 50 ml of water. However, her friend predicted that adding only 10 ml of water will help the seeds to germinate faster. Which of the following set-ups should Siti use to provide a correct test for both their predictions?

Accepted Answer

D. A and B each have a mix of cotton wool with 50 ml water and cotton wool with 10 ml water, A contains dark seeds and B contains round seeds. To test both predictions (50 ml vs 10 ml water) fairly, the same type of seed must be tested with both water amounts. Only set-up (4) places the same type of seed (dark seeds in A, round seeds in B) on both 50 ml and 10 ml water cotton wool within each container — this allows comparison of germination time between the two water volumes for each seed type, testing both predictions.

Question 15

The diagram below shows Substance X in a container at various temperatures. Based on the above information, which one of the following is the melting point of Substance X?

Accepted Answer

C. 32°C. At 10°C and 28°C Substance X is solid (hard then soft). At 32°C it has become liquid and at 40°C it is fully liquid. Melting occurs between 28°C (still solid/soft) and 32°C (liquid). The temperature at which it becomes a liquid is 32°C, so that is the melting point.

Question 16

The diagram shows what a person can do. This shows the property of ____.

Accepted Answer

C. flexibility. The person is bending backwards. The ability of the body to bend without breaking shows the property of flexibility.

Question 17

Mrs Tan realises that there is fogging on her spectacles when she wears her mask as shown. Which of the following correctly shows where the fogging takes place and where the warmer water vapour comes from?

Accepted Answer

A. Fogging on the inner surface; warmer water vapour from Mrs Tan's breath. When Mrs Tan exhales, warm water vapour from her breath escapes upward from the top of the mask. This warm vapour meets the cooler inner surface of her spectacles, where it loses heat and condenses into water droplets, causing fogging on the inner surface.

Question 18

Diagram 1 shows the mass of magnet M when it is placed on an electronic balance. Diagram 2 shows its mass when another object Y is placed above it. Which of the following shows the material of object Y and the direction of the magnetic force acting on object Y?

Accepted Answer

C. steel; arrow pointing downward. The mass of magnet M decreased from 20.0 g to 18.0 g when object Y was placed above it. This means object Y is pulling the magnet upward (a magnetic force of attraction between M and Y). For this attraction to occur, Y must be a magnetic material — steel. By Newton's third law, the magnetic force from the magnet acts downward on object Y (pulling Y toward the magnet which is below it). The arrow on Y therefore points downward.

Question 19

Three children were making shadow animals with their hands. They placed their hands which were of the same size at positions X, Y and Z between a light source and a wall as shown below. The size of each shadow animal was seen on the wall as shown below. Which of the following shows the positions of the children's hands, X, Y and Z?

Accepted Answer

A. reindeer X, rabbit Y, snail Z. The closer the hand (opaque object) is to the light source, the larger the shadow on the wall. From the diagram, X is closest to the light source, Y is in the middle and Z is the furthest. So X produces the largest shadow (reindeer), Y produces a medium-sized shadow (rabbit) and Z produces the smallest shadow (snail).

Question 20

Dan released a tennis ball and a basketball each from the same height above the ground. The balls hit on the ground and bounced a few times before stopping. He measured the height of the first rebound for each ball as shown below. Next, he placed the tennis ball on top of the basketball as shown below before releasing them from the same height. He observed that the tennis ball bounced higher into the air than before as shown below. Which one of the following is the best explanation for his observation?

Accepted Answer

D. The elastic potential energy of the compressed basketball when it hit the ground was converted to kinetic energy of the tennis ball.. When the basketball (with the tennis ball on top) hits the ground, the basketball is compressed and stores elastic potential energy. As it returns to its original shape, this elastic potential energy is transferred to the tennis ball as kinetic energy, propelling the tennis ball upward higher than before.

Question 21

Which one of the following is an example of the effect of a force?

Accepted Answer

A. Leaves falling from a tree.. Leaves falling from a tree is the effect of gravitational force pulling them down. Melting, cooking and evaporating are effects of heat gain (a transfer of energy), not a force.

Question 22

The diagram shows a cylinder and a plunger. When the cylinder was filled with substance P, the plunger was able to be pushed down to a certain extent but not when it was filled with substance Q. Based on the observations, which of the following are correct? A Substance Q has definite volume. B Substance Q has a definite shape. C There are air spaces in substance P.

Accepted Answer

B. A and C only. The plunger could be pushed down on P (so P has air spaces and can be compressed) — P is a gas. C is true. The plunger could not be pushed down on Q — Q is a liquid which has definite volume but no definite shape (takes the shape of its container). A is true. B is false because Q is liquid, not solid.

Question 23

The diagram below shows the different processes, A, B, C, D, E and F, in a water cycle. Which one of the following is correct?

Accepted Answer

B. Involve a change of state: A, B and F; Involve(s) heat loss: B. A is evaporation (water on Earth → water vapour) — change of state, heat gain. B is condensation (water vapour → clouds) — change of state, heat loss. C is precipitation (clouds → rain) — no change of state, no heat loss. D and E are water flow — no change of state. F is transpiration/evaporation (plant releases water vapour) — change of state, heat gain. So A, B and F all involve change of state, and only B involves heat loss.

Question 24

Ahmad wanted to find out how the volume of water will affect the temperature of hot water over a period of time. He used four identical containers to set up P, Q, R and S as shown below. Which two set-ups should he use for his experiment?

Accepted Answer

B. P and R only. To investigate how the volume of water affects the temperature, only the volume of water must change; all other variables (starting temperature) must be kept the same. Set-ups P (500 ml at 100°C) and R (250 ml at 100°C) have the same starting temperature but different volumes, so they form a fair test.

Question 25

There were two identical cups, A and B, containing same amount of hot water on a table. The water was at the same temperature in both cups. Bala placed a piece of bubble wrap onto cup A as shown in the diagram below. After five minutes, Bala observed that the water in cup A had a higher temperature than that in cup B. Which of the following could be the most likely reason for the observation above?

Accepted Answer

D. The bubble wrap reduced the heat transfer from the water in cup A to the surroundings.. The bubble wrap acts as an insulator (with trapped air pockets that are poor conductors of heat) and a lid that reduces evaporation. It reduces the rate of heat loss from the hot water in cup A to the surroundings, so the water in A remains hotter than in cup B.

Question 26

Study the circuit. Which bulb when blown allows the other three bulbs to remain lit?

Accepted Answer

A. W. W is in parallel with the rest of the circuit (with X, Y and Z in their own arrangement). If W is blown, current can still flow through the remaining branch containing X, Y and Z, so the other three bulbs stay lit. Blowing X, Y or Z would break the only path through their loop, affecting the others.

Question 27

Ravi placed a book on a wooden plank as shown in Diagram 1. He raised the wooden plank till the book starts to slide down and then he measured the angle of plank as shown in Diagram 2. The table below shows the results for different types of wooden planks, A, B and C. Wooden Plank A: 20°; B: 70°; C: 50°. Which of the following correctly shows the relationship between the angle of plank and the amount of friction between the plank and the book?

Accepted Answer

B. Three lines all increasing, B highest, then C, then A (B>C>A friction at any angle, all starting from origin) — with all positive slopes from origin. The greater the angle of plank required before the book starts to slide, the greater the friction between the book and the plank. From the table: B (70°) has the most friction, C (50°) next, A (20°) the least. So at any given angle the line for B is highest, then C, then A — and friction increases as the angle of plank increases (positive slope from origin).

Question 28

Asri used a trolley to push some boxes for delivery. He was able to push the trolley faster after each box was delivered. Which of the following explain the phenomenon? A There was less friction between the trolley and the floor. B He has to overcome less gravitational force between the trolley and the Earth. C More kinetic energy of Asri was converted to more kinetic energy of the trolley.

Accepted Answer

B. A and C only. After each box is delivered, the trolley is lighter. With less weight pressing the trolley onto the floor, there is less friction between the trolley and the floor (A true). Asri exerts roughly the same effort (kinetic energy), but with a lighter trolley a greater proportion is converted to the trolley's kinetic energy, making it move faster (C true). The gravitational force is not 'overcome' when pushing a trolley along a flat floor — gravity acts downward, not against the push (B false).

P6 Science SA2 2020 — Rosyth

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