Question 1

Study the table below.

Which of the following is/are grouped wrongly?

Accepted Answer

D. water vapour and cloud only. Water vapour is a gas, not a liquid — so it is wrongly placed in the Liquid column. Cloud is made of tiny liquid water droplets (not gas) — so it is wrongly placed in the Gas column. Both 'water vapour' and 'cloud' are grouped wrongly.

Question 2

The diagrams below show a fish and a human respiratory system. At which parts of the fish and human respiratory system is oxygen absorbed into the bloodstream?

Accepted Answer

D. Human: Q, Fish: T. In humans, oxygen is absorbed into the bloodstream at the lungs (labelled Q — specifically at the alveoli). In fish, oxygen is absorbed at the gills (labelled T). So the answer is Human Q, Fish T.

Question 3

Josh cut the stalk of a white flower into two halves and placed each end into separate beakers containing blue and red coloured water as shown below. He then left the set-up for 12 hours. Which of the following would he observe after 12 hours?

Accepted Answer

D. Part A turned blue while part B turned red.. The stalk is split into two halves, so each half is connected to only one beaker. Part A draws water from the blue beaker through its water-carrying tubes (xylem), causing its petals to turn blue. Part B draws water from the red beaker, causing its petals to turn red.

Question 4

An inflatable bag with a capacity of 1000 ml was first filled with 900 ml of substance X. The same bag was then filled with an additional 110 ml of substance Y and the bag did not burst. The experiment was repeated but substance Z was used instead of substance Y and the bag burst. Which of the following statements below is true?

Accepted Answer

A. Substance Y is a gas.. Total volume after adding Y = 900 + 110 = 1010 ml, but the bag (capacity 1000 ml) did not burst. This means Y could be compressed to fit, so Y must be a gas (gases can be compressed). When Z was added the bag burst, meaning Z could not be compressed — Z is a liquid. X is the original substance occupying 900 ml; since Y (the gas) compressed to share the space with X, X is also a gas, but the only option that is definitely true given the choices is that Y is a gas.

Question 5

The table below shows the melting point and boiling point of three substances.

| Substance | Q | R | S |
| Melting point (°C) | 20 | 10 | 30 |
| Boiling point (°C) | 140 | 50 | 170 |

Which of the following statement below is true?

Accepted Answer

C. Substance Q and R can be compressed at 150 °C.. At 150 °C: Q (boiling point 140 °C) has boiled into a gas; R (boiling point 50 °C) has long boiled into a gas; only S (boiling point 170 °C) is still a liquid. Gases can be compressed, so both Q and R can be compressed at 150 °C. Option A is wrong because R (boiling point 50 °C) is a gas at 90 °C, not a liquid. Option B is wrong because at 40 °C only R has boiled — but R is a gas which can be compressed, while Q is a liquid (40 °C is between melting 20 and boiling 140) and S is a solid (40 °C above melting 30 but below boiling 170, so S is liquid). Option D is wrong because at 15 °C, R (mp 10) is a liquid but Q (mp 20) and S (mp 30) are solids with definite shapes.

Question 6

Eight adults were trapped in a lift for about an hour. The graph below shows the volume of gases X, Y and Z in the lift. Which of the following correctly identifies gases X, Y and Z?

Accepted Answer

C. X: nitrogen, Y: carbon dioxide, Z: oxygen. The adults are breathing inside a sealed lift. Nitrogen (X) stays approximately constant because it is not used by respiration. Carbon dioxide (Y) increases over time because the adults breathe it out. Oxygen (Z) decreases over time because the adults breathe it in for respiration. So X = nitrogen, Y = carbon dioxide, Z = oxygen.

Question 7

The diagrams below show a human circulatory system and a plant transport system. The arrows represent the movement of substances in both systems. The human diagram shows arrows from lungs → heart → small intestine, with an arrow labelled P between heart and small intestine. The plant diagram shows arrows roots → stem → leaves, with an arrow labelled Q between roots and stem. Which of the following correctly represents P and Q?

Accepted Answer

B. P: digested food, Q: food. Looking at the diagrams: in the human diagram, the arrow P points from the small intestine toward the heart — the substance carried from the small intestine into the bloodstream is digested food (absorbed through villi). In the plant diagram, the arrow Q points from the stem toward the roots — food made in the leaves travels down via the food-carrying tubes (phloem) through the stem to the roots, so Q represents food.

Question 8

Lilian removed the outer ring of the stem of a plant as shown in the diagram below. After one week, she observed a swell above part X. Which tube was removed to cause the swell above part X and what was the correct explanation for her observation?

Accepted Answer

A. Tube removed: food-carrying tube. Explanation: Food made by the leaves could not be transported below part X so it was stored above part X.. The food-carrying tubes (phloem) are located in the outer ring of the stem. When the outer ring is removed at part X, food made by the leaves (via photosynthesis) cannot pass through that gap to reach the parts of the plant below X. The food accumulates and is stored above part X, causing the swelling.

P5 Science CA2 2023 — Maha Bodhi

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