Question 1

Study the following electric circuits. If all the bulbs and batteries are in working condition and are identical, in which circuit will the bulb(s) be the brightest?

Accepted Answer

B. Circuit (2). Circuit (2) has two batteries in series (more electrical energy) and two bulbs in parallel. With batteries in series, voltage doubles; with bulbs in parallel, each bulb receives the full battery voltage, so bulbs are brightest in this set-up.

Question 2

The diagram shows a light bulb. Which parts of the bulb are good conductors of electricity?

Accepted Answer

C. B, C and D only. Part A is the filament (tungsten - conductor), B is the metal contact wire, C is the metal screw base, D is the metal tip - all conductors except the glass insulator portion. Parts B, C and D are the metal conducting parts; the glass bead supporting the filament is an insulator.

Question 3

Which of the following circuit(s) is / are closed?

Accepted Answer

B. C and D only. A closed circuit requires conductors throughout. Circuit A has glass (insulator) - open. Circuit B has plastic sheet (insulator) - open. Circuit C has copper coin (conductor) - closed. Circuit D has iron nail (conductor) - closed. Only C and D are closed circuits.

Question 4

Kenny wants to find out how the number of batteries affects the brightness of a bulb. Which two of the set-ups should he use?

Accepted Answer

A. A and C. To investigate how the number of batteries affects bulb brightness, only the number of batteries should change while the number of bulbs is kept constant. Set-up A has 2 batteries with 1 bulb; Set-up C has 1 battery with 1 bulb. Both have one bulb, only the number of batteries differs - making them the correct fair comparison.

Question 5

Study the circuit below. Which of the bulbs will still light up when bulb D fuses?

Accepted Answer

B. A, B and C only. Bulbs D and E are in series with each other on the same branch, so when D fuses the D-E branch is broken and E also goes off. Bulbs A, B and C are on separate parallel branches that remain closed, so they continue to light.

Question 6

The circuit card has a metal thumbtack at each of the points A, B, C, D and E. Some of the thumbtacks are connected by wires behind the card. To find out how these thumbtacks are connected, the two ends of the circuit tester are connected to two different thumbtacks each time. The results are shown in the table below. (A and D: No, B and D: Yes, C and E: Yes). From the results shown in the table above, which one of the following is a possible arrangement of the wires behind the circuit card?

Accepted Answer

A. Arrangement (1). The arrangement must satisfy: A and D not connected (No), B and D connected (Yes), C and E connected (Yes). Arrangement (1) shows wire from B through C to D (so B-D and C-D connected via C, but also B-C-D path makes C-E need a separate connection - actually arrangement 1 shows B-C-D connection AND D-E connection, with A isolated, giving A-D: No, B-D: Yes (via C), C-E: Yes (via D-E path). This matches all three test outcomes.

Question 7

In which of the circuits will both the bulbs light up?

Accepted Answer

B. Circuit (2). For both bulbs to light up, both must be part of a complete closed circuit with correct contacts on the metal tip and metal screw of each bulb. Circuit (2) is the only set-up where both bulbs have one wire to the metal tip and one to the metal screw, completing the circuit for both bulbs.

Question 8

Which of the following actions helps to conserve electricity?

Accepted Answer

B. Setting the air conditioner to 25°C instead of 19°C.. Setting the air conditioner to a higher temperature (25°C instead of 19°C) means it uses less electricity to cool the room, conserving electricity. The other options waste electricity.

Question 9

The diagram shows an electric circuit. To light up bulb X only, which of the switches should be closed?

Accepted Answer

B. S2 and S4 only. Bulb X is on the branch controlled by switch S4. S2 must be closed to complete the main loop back to the battery. S1 and S3 control the other two bulbs - keeping them open means only bulb X lights up. Therefore close S2 and S4 only.

Question 10

Christian wants to investigate how the arrangement of the bulbs will affect the brightness of the bulb. Which two circuits should he use for his experiment?

Accepted Answer

B. A and C. To investigate how arrangement of bulbs affects brightness, only the bulb arrangement (series vs parallel) should differ while number of batteries and number of bulbs remain constant. Circuit A has 1 battery + 2 bulbs in series; Circuit C has 1 battery + 2 bulbs in parallel. Same number of batteries and bulbs, only arrangement differs.

Question 11

In the diagram below, letters A, B, C and D represents blood vessels carrying blood to and from the lungs, heart and other parts of the body. Which two blood vessels carry blood rich in oxygen?

Accepted Answer

A. A and B only. In the diagram, A carries oxygenated blood from the lungs to the heart (the pulmonary vein pathway) and B carries oxygenated blood from the heart to the other parts of the body (the aorta pathway). C carries deoxygenated blood from the heart back to the lungs and D returns deoxygenated blood from the body to the heart. Hence A and B are the oxygen-rich vessels.

Question 12

Which of the following statements about the air around us is true?

Accepted Answer

C. It has less carbon dioxide than nitrogen.. Air is approximately 78% nitrogen, 21% oxygen, and only a small amount (~0.04%) of carbon dioxide along with other gases and varying water vapour. Therefore there is much less carbon dioxide than nitrogen in air, making statement C true.

Question 13

Which of the following statement(s) about the respiratory system is/are correct? A. The nose hairs trap dust. B. The respiratory system helps to remove carbon dioxide from the body. C. The main organs in the respiratory system consist of the nose, gullet and lungs.

Accepted Answer

B. A and B only. Statement A is correct - nose hairs trap dust particles. Statement B is correct - the respiratory system removes carbon dioxide during exhalation. Statement C is wrong because the gullet (oesophagus) belongs to the digestive system, not the respiratory system; the main respiratory organs are the nose, windpipe and lungs. So only A and B are correct.

Question 14

Colin ran a 100-metre race. Which one of the following graphs shows the likely change in his heartrate during the race?

Accepted Answer

D. Graph (4). During a 100-metre sprint, the body needs more energy quickly, so the heart beats faster to supply more oxygen and digested food to the muscles. Heart rate therefore rises rapidly from rest and then levels off at a high value - this matches Graph (4), which shows an increasing curve that plateaus.

Question 15

What is the organ involved in gaseous exchange that is found at X?

Accepted Answer

B. Gills. The diagram shows a fish, and X points to the area behind the head where the gills are located. Gills are the organ of gaseous exchange in fish - they absorb dissolved oxygen from water and release carbon dioxide.

Question 16

The diagram below shows a model of the human respiratory system. What do A and B represent?

Accepted Answer

D. A: Windpipe, B: Lungs. In the bell-jar model of the respiratory system, the glass tube entering the top of the jar represents the windpipe (trachea) - that is A. The balloons inside the jar represent the lungs - that is B. The rubber sheet at the bottom represents the diaphragm.

Question 17

Keith cut the outer ring of the stem of a plant as shown in Figure A. Two days later, a swelling was observed only above the cut region as shown in Figure B. Which one of the following statements best explains the swelling?

Accepted Answer

A. Food had accumulated above the cut region.. The outer ring of the stem contains the food-carrying tubes (phloem). Cutting the outer ring breaks the phloem, so food made in the leaves can no longer be transported downwards past the cut. Food accumulates above the cut region, causing the swelling. Water-carrying tubes (xylem) are in the inner stem and are not affected.

Question 18

John observed the underside of the leaf and saw many tiny openings as shown in the diagram. Which two of the following statement(s) below about these tiny openings are true? A. It allows gaseous exchange in the day only. B. It allows water vapour to escape the leaves. C. It allows gaseous exchange in the day and night. D. It allows water vapour to enter for photosynthesis.

Accepted Answer

C. B and C. The tiny openings are stomata. Stomata allow gaseous exchange both in the day and at night (statement C is true - oxygen/CO2 exchange occurs continuously, though the gases differ between day and night). They also allow water vapour to escape during transpiration (statement B is true). Statement D is false because water enters the plant through roots, not through stomata, and photosynthesis needs CO2 (not water vapour entering through stomata).

Question 19

The diagram shows a growing seedling. The structure marked X always grows in the direction where there is ____.

Accepted Answer

D. water. Structure X is the root of the seedling. Roots always grow downwards towards water and gravity (positive hydrotropism and gravitropism) to absorb water and mineral salts for the plant. They do not grow towards light - shoots do.

Question 20

Alvin set up an experiment as shown. Firstly, he split part of a plant stem in half. Then, he put one half of it in a beaker of water mixed with blue dye and the other half in a beaker of water. After some time, half of the flower turned blue. Which of the following is/are also transported to the rest of the plant by tubes in the plant's stem that caused half of the flower to turn blue? A. food B. oxygen C. mineral salts D. carbon dioxide

Accepted Answer

A. C only. The blue dye travelled through the water-carrying tubes (xylem) in the stem. Xylem transports water and mineral salts from the roots upward to the rest of the plant. So besides water/dye, only mineral salts (C) are also transported by these tubes. Food is transported by phloem, not xylem; oxygen and carbon dioxide are not transported through these tubes.

P5 Science SA1 2023 — Anglo Chinese

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