Section A — Multiple Choice (30 marks)
Choose the BEST answer. Click 点击显示答案 to check.
Which two gases make up approximately 99% of dry air?
A. Oxygen and carbon dioxide
B. Nitrogen and oxygen
C. Nitrogen and argon
D. Oxygen and water vapour
The word equation for photosynthesis is:
A. Carbon dioxide + water → glucose + oxygen
B. Glucose + oxygen → carbon dioxide + water
C. Carbon dioxide + oxygen → glucose + water
D. Oxygen + water → glucose + carbon dioxide
An animal cell carries out aerobic respiration. Which gas does it take in and which gas does it release?
A. Carbon dioxide | Oxygen
B. Nitrogen | Carbon dioxide
C. Oxygen | Carbon dioxide
D. Oxygen | Water vapour
The diagram below shows part of the human respiratory system.
A. Nose → trachea → bronchi → alveoli
B. Nose → bronchi → trachea → alveoli
C. Mouth → alveoli → bronchi → trachea
D. Nose → trachea → alveoli → bronchi
In a leaf, most gas exchange occurs through:
A. The upper epidermis
B. The veins
C. The stomata
D. The chloroplasts
Which human activity would MOST directly increase the carbon dioxide concentration in the atmosphere?
A. Planting trees in a forest
B. Burning fossil fuels in a power station
C. Using solar panels to generate electricity
D. Recycling paper and plastic
Which of the following is a health problem caused by poor air quality?
A. Broken bones
B. Asthma
C. Tooth decay
D. Colour blindness
The diagram shows a circuit with a cell, a switch, and a bulb.
A. Current flows and the bulb lights up
B. Current flows but the bulb does not light up
C. No current flows and the bulb does not light up
D. No current flows but the bulb still lights up
Which of the following is a CONDUCTOR of electricity?
A. Rubber
B. Plastic
C. Copper
D. Wood
In a series circuit with two identical bulbs and one cell, what happens when one bulb is removed?
A. The other bulb stays on, same brightness
B. The other bulb stays on, but brighter
C. The other bulb goes out
D. The other bulb stays on, but dimmer
Which circuit symbol represents a battery?
A. Two parallel lines of different lengths (long and short)
B. A circle with a cross inside
C. A straight line with a gap
D. A zigzag line
Voltage is a measure of:
A. The amount of current flowing through a circuit
B. The energy given to each unit of charge
C. The opposition to current flow
D. The brightness of a bulb
Which material has the HIGHEST resistance?
A. Copper wire
B. Iron wire
C. Rubber
D. Sea water
The purpose of a fuse in a household circuit is to:
A. Increase the current flowing through the circuit
B. Measure the amount of electricity used
C. Melt and break the circuit if the current becomes too high
D. Convert AC to DC electricity
Which of the following is a SAFE practice when using electricity at home?
A. Plugging many devices into one multi-way adaptor
B. Touching a bare wire while the switch is on
C. Using a device that has a damaged, frayed cable
D. Switching off and unplugging an appliance before cleaning it
A 60 W bulb is left on for 5 hours. The electrical energy consumed is:
A. 60 J
B. 300 J
C. 60 Wh
D. 300 Wh
Which appliance typically uses the MOST electrical energy in a home per month?
A. A bedside lamp
B. A television
C. An air conditioner
D. A mobile phone charger
A substance has a pH of 2. Which statement is true?
A. It is a strong alkali
B. It is a weak alkali
C. It is a strong acid
D. It is neutral
Universal indicator turns GREEN when added to a solution. The solution is:
A. Strongly acidic
B. Neutral
C. Strongly alkaline
D. Weakly acidic
The reaction between hydrochloric acid and sodium hydroxide is called:
A. Combustion
B. Evaporation
C. Neutralisation
D. Corrosion
Which hazard symbol would you expect to see on a bottle of concentrated sulfuric acid?
A. A flame
B. A skull and crossbones
C. A hand being corroded / test tube pouring liquid onto a hand
D. An exclamation mark
If a student accidentally splashes dilute acid onto their skin, the FIRST thing they should do is:
A. Rub the area with a cloth
B. Wash the area with plenty of water
C. Add alkali to neutralise the acid
D. Inform the teacher after the lesson
Farmers sometimes add lime (calcium oxide) to soil. The purpose is to:
A. Make the soil more acidic
B. Neutralise acidic soil
C. Add fertiliser to the soil
D. Kill pests in the soil
A doctor prescribes an antacid tablet for a patient. The tablet MOST likely contains a:
A. Weak acid
B. Strong acid
C. Weak alkali
D. Neutral substance
Which part of the eye focuses light onto the retina?
A. Iris
B. Pupil
C. Lens
D. Optic nerve
The function of the cochlea in the human ear is to:
A. Collect sound waves from the air
B. Amplify vibrations from the eardrum
C. Convert sound vibrations into electrical signals
D. Help maintain balance
Which statement about the sense of taste is TRUE?
A. All parts of the tongue detect all tastes equally
B. Different regions of the tongue have different types of taste receptors
C. Taste receptors are located only on the tip of the tongue
D. Taste and smell are completely independent senses
Which part of the brain is responsible for coordinating balance and voluntary movement?
A. Cerebrum
B. Cerebellum
C. Brain stem
D. Spinal cord
When you accidentally touch a hot object, you pull your hand away quickly. This response is an example of:
A. A voluntary action controlled by the cerebrum
B. A reflex action controlled by the spinal cord
C. A learned response from past experience
D. An involuntary action controlled by the cerebellum
Which sense organ contains receptors that detect pressure, temperature, and pain?
A. The ear
B. The nose
C. The skin
D. The tongue
Section B — Structured Questions (40 marks)
Air Composition
The table below shows the approximate composition of dry air.
| Gas | Percentage (%) |
|-----|---------------|
| Nitrogen | 78 |
| Oxygen | 21 |
| Other gases | 1 |
(a) Name ONE gas found in the "Other gases" category. (1)
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(b) Explain why nitrogen gas is important for plant growth, even though plants cannot use nitrogen gas directly from the air. (2)
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(a) Carbon dioxide / Argon / Neon / Helium / Krypton / Xenon (any one) [1]
(b) Nitrogen is needed by plants to make proteins / for growth (1). Bacteria in the soil / lightning converts nitrogen gas into compounds that plants can absorb (1).
Photosynthesis Experiment
A student set up three test tubes containing pondweed (an aquatic plant) as shown below.
| Test Tube | Conditions | Bubbles per minute |
|-----------|-----------|-------------------|
| A | Bright light + water | 25 |
| B | Bright light + water + sodium hydrogen carbonate (CO₂ source) | 48 |
| C | Dark cupboard + water | 0 |
(a) Name the gas being produced by the pondweed. (1)
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(b) Explain why Test Tube C produced no bubbles. (2)
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(c) Compare Test Tubes A and B. What conclusion can you draw about the effect of adding sodium hydrogen carbonate? (2)
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(a) Oxygen [1]
(b) Photosynthesis requires light energy (1). In the dark, the plant cannot photosynthesise / no light for photosynthesis, so no oxygen is produced (1).
(c) Adding sodium hydrogen carbonate (CO₂ source) increased the rate of photosynthesis (1). This shows that carbon dioxide is a raw material / limiting factor for photosynthesis (1).
Aerobic Respiration
(a) Write the word equation for aerobic respiration. (2)
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(b) A runner breathes faster and deeper during a race. Explain why this is necessary for her muscle cells. (2)
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## Unit 8: Making Use of Electricity (12 marks)
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(a) Glucose + Oxygen → Carbon dioxide + Water (+ Energy) [2 — 1 for correct reactants, 1 for correct products]
(b) During exercise, muscles need more energy for contraction (1). Faster breathing supplies more oxygen for aerobic respiration to release more energy / removes more carbon dioxide (1).
Circuit Diagrams
Draw a circuit diagram showing:
- A cell
- A switch (open)
- Two bulbs connected in series
Use the correct circuit symbols.
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- Cell symbol (long + short parallel lines): 1 mark
- Open switch (gap): 1 mark
- Two bulbs in series (circles with cross/X): 1 mark
- Wires connecting all components in one continuous loop
Series vs Parallel
Two circuits are built with identical cells and identical bulbs.
- Circuit X: Two bulbs connected in series
- Circuit Y: Two bulbs connected in parallel
(a) In which circuit are the bulbs brighter? Explain why. (3)
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(b) In Circuit Y, one bulb blows (breaks). What happens to the other bulb? Explain why. (2)
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(a) Circuit Y (parallel) has brighter bulbs (1). In a parallel circuit, each bulb receives the full voltage of the cell (1). In a series circuit, the voltage is shared / divided between the two bulbs (1).
(b) The other bulb stays on (1). In a parallel circuit, each bulb has its own separate path / loop for current, so current still flows through the other bulb (1).
Conductors and Insulators
A student builds a simple circuit with a cell, bulb, and two crocodile clips. She tests different materials by placing them between the clips.
| Material | Bulb lights up? |
|----------|----------------|
| Iron nail | Yes |
| Plastic ruler | No |
| Pencil lead (graphite) | Yes |
| Glass rod | No |
(a) From the table, name a **conductor** and an **insulator** of electricity. (1)
Conductor: ____________________ Insulator: ____________________
(b) Explain why graphite conducts electricity even though it is a non-metal. (2)
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(c) Suggest ONE reason why electrical wires are covered in plastic. (1)
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## Unit 9: Acids and Alkalis (8 marks)
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(a) Conductor: Iron nail OR Pencil lead / graphite (1). Insulator: Plastic ruler OR Glass rod (1).
(b) Graphite has delocalised / free-moving electrons that can carry electric charge (1). The layers of carbon atoms in graphite allow electrons to flow (1).
(c) Plastic is an insulator (1) — it prevents electric shock / prevents current from leaking / protects the user from touching live wire (any reasonable safety reason).
pH Scale and Indicators
The pH values of four household substances are shown below.
| Substance | pH |
|-----------|-----|
| Lemon juice | 2 |
| Pure water | 7 |
| Soap solution | 9 |
| Oven cleaner | 13 |
(a) Which substance is the STRONGEST alkali? (1)
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(b) A drop of universal indicator is added to each substance. State the colour produced for **lemon juice** and **pure water**. (2)
Lemon juice: ____________________
Pure water: ____________________
(c) Lemon juice and soap solution are mixed together. Predict the pH of the mixture and explain your answer. (1)
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(a) Oven cleaner [1]
(b) Lemon juice: Red / orange / red-orange (1). Pure water: Green (1).
(c) pH between 2 and 9 (e.g., pH 5–7) because the acid (lemon juice) and alkali (soap) neutralise each other (1).
Neutralisation in Daily Life
(a) A gardener finds that his soil is too acidic (pH 5.0) for growing tomatoes. He adds garden lime to the soil. Explain how lime helps the soil become suitable for tomatoes. (2)
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(b) A student has a stomach ache caused by excess stomach acid. She takes a tablet containing magnesium hydroxide. Using your knowledge of neutralisation, explain how the tablet relieves the pain. (2)
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## Unit 10: Sensing the Environment (8 marks)
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(a) Lime is alkaline (1). It neutralises the excess acid in the soil, raising the pH to a level suitable for growing tomatoes (1).
(b) Magnesium hydroxide is an alkali / base (1). It neutralises the excess hydrochloric acid in the stomach, relieving the pain (1).
Eye Structure and Function
The diagram below shows the human eye (simplified).
| Label | Structure |
|-------|----------|
| A | Pupil |
| B | Lens |
| C | Retina |
| D | Optic nerve |
(a) Describe the function of structure B (the lens). (1)
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(b) In bright light, the pupil becomes smaller. Explain why this happens. (2)
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(c) What is the role of the optic nerve (D)? (1)
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(a) The lens focuses / bends light onto the retina (1).
(b) In bright light, the circular muscles of the iris contract (1), making the pupil smaller to reduce the amount of light entering the eye / to protect the retina from damage (1).
(c) The optic nerve carries electrical signals / impulses from the retina to the brain (1).
Nerve Pathway
A student sees a ball rolling towards her and catches it.
(a) Name the **sense organ** and the **type of receptor** involved in detecting the ball. (1)
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(b) Arrange the following structures into the correct order for this response: (2)
*Brain, Eye, Muscle in hand, Sensory neuron, Motor neuron*
Order: _______ → _______ → _______ → _______ → _______
(c) Explain why using TWO eyes helps the student judge the distance of the ball better than using one eye. (1)
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(a) Eye, light receptors / photoreceptors (1)
(b) Eye → Sensory neuron → Brain → Motor neuron → Muscle in hand (2)
(c) Using two eyes provides stereoscopic / binocular vision (1), which gives depth perception and allows the brain to judge distance more accurately.
Section C — Application & Data Analysis (20 marks)
Graph Interpretation: Rate of Photosynthesis
A scientist investigated the effect of light intensity on the rate of photosynthesis in a plant. The results are shown below.
| Light Intensity (arbitrary units) | Rate of Photosynthesis (bubbles per minute) |
|----------------------------------|---------------------------------------------|
| 0 | 0 |
| 20 | 8 |
| 40 | 16 |
| 60 | 24 |
| 80 | 30 |
| 100 | 32 |
| 120 | 32 |
(a) Plot a line graph of these results on the grid provided. (3)
(b) Describe the trend shown by the graph. (2)
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(c) Suggest why the rate of photosynthesis stops increasing after a light intensity of 100 units. (1)
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(a) Graph (3 marks):
- Axes labelled correctly (Light Intensity on x-axis, Rate of Photosynthesis on y-axis) with units: 1 mark
- Points plotted correctly (± half small square): 1 mark
- Line of best fit drawn (straight line from 0 to ~80, then curve flattening at 100–120): 1 mark
(b) As light intensity increases, the rate of photosynthesis increases (1). However, after light intensity reaches about 80–100 units, the rate levels off / stops increasing (1).
(c) Another factor (e.g., carbon dioxide concentration or temperature) has become the limiting factor (1). The plant cannot photosynthesise faster even with more light.
Experiment Interpretation: Effect of Exercise on Breathing Rate
A student measured his breathing rate (breaths per minute) before, during, and after 3 minutes of exercise.
| Time (minutes) | Activity | Breathing rate (breaths/min) |
|---------------|----------|------------------------------|
| 0 | Resting | 14 |
| 1 | Exercising | 20 |
| 2 | Exercising | 26 |
| 3 | Exercising | 32 |
| 4 | Recovering | 24 |
| 5 | Recovering | 18 |
| 6 | Recovering | 15 |
(a) Calculate the increase in breathing rate from resting (0 min) to the end of exercise (3 min). (1)
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(b) Explain why the breathing rate increased during exercise. (2)
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(c) After exercise, the breathing rate gradually returns to normal. What does this tell you about the body's ability to regulate itself? (2)
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(a) 32 − 14 = 18 breaths per minute (1)
(b) During exercise, muscles respire faster / need more energy (1). More oxygen is needed for aerobic respiration and more carbon dioxide needs to be removed, so breathing rate increases (1).
(c) The body can return to its normal resting state after exercise (1). This shows the body has homeostatic / self-regulating mechanisms to maintain balance / recover (1).
Experimental Design: Testing Conductivity of Solutions
A student wants to test whether different liquids conduct electricity. She sets up a circuit with a cell, a bulb, and two wires with bare ends placed in a beaker of liquid.
(a) State ONE variable that must be kept the same for a fair test. (1)
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(b) The student tests tap water and salt water. The bulb glows dimly in tap water but brightly in salt water. Explain this difference. (2)
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(c) The student wants to test if sugar solution conducts electricity. Predict the result and give a reason. (2)
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(a) Any one of: voltage of cell / type of cell / distance between wires in liquid / temperature / amount of liquid / concentration of solution (1)
(b) Tap water contains dissolved salts / minerals / ions that conduct electricity slightly (1). Salt water has more dissolved ions (Na⁺ and Cl⁻) that carry charge, so it conducts much better (1).
(c) Sugar solution will NOT conduct electricity (or conduct very poorly) (1). Sugar dissolves as molecules / does not produce ions, so there are no free-moving charged particles to carry the current (1).
Real-Life Scenario: Household Electricity
Mr. Chen's house has a 13 A fuse in the plug of his 800 W microwave oven. The household voltage is 220 V.
(a) Calculate the current drawn by the microwave oven using the formula: **Power = Current × Voltage** (2)
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(b) Is the 13 A fuse suitable for this microwave oven? Explain your answer. (1)
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(c) Suggest what might happen if a fuse with a lower rating, such as 3 A, was used instead. (1)
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(a) Current = Power ÷ Voltage = 800 ÷ 220 = 3.64 A (2 marks — 1 for correct substitution, 1 for correct answer)
(b) Yes, because 3.64 A is less than 13 A, so the fuse will not blow during normal operation / the fuse rating is higher than the normal operating current (1).
(c) The 3 A fuse would blow / melt / break the circuit during normal operation (1). This would be an inconvenience as the microwave would keep switching off (1). (Accept: the fuse would not be suitable because the normal current (3.64 A) exceeds the fuse rating.)
Section D — Higher Order Thinking (10 marks)
Cross-Topic Analysis: Plants, Respiration, and pH
A student places a snail and a plant in a sealed transparent container. The container is placed in sunlight.
(a) Explain why the snail can survive inside the sealed container for several days. (2)
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(b) Predict what would happen to the snail if the container was placed in a dark cupboard for several days. Explain your answer. (3)
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(a) The plant photosynthesises using sunlight, producing oxygen (1). The snail uses this oxygen for respiration and produces carbon dioxide, which the plant uses for photosynthesis (1). They create a balanced gas exchange cycle.
(b) In the dark, the plant cannot photosynthesise, so it stops producing oxygen (1). The plant continues to respire, using oxygen and producing carbon dioxide (1). Both the snail and the plant consume oxygen, so oxygen levels will drop, and the snail will die from lack of oxygen / suffocation (1).
Evaluation: Circuit Design for a School Project
A student is building a model house that needs:
- A main light in the living room that can be turned on/off by itself
- Two identical lights in the bedroom that both come on together and go off together
The student has one battery, three bulbs, wires, and two switches.
(a) Draw a circuit diagram that meets all the requirements. Label which switch controls which room. (3)
(b) If the bedroom lights are connected in series, and one bulb blows, what happens to the other bedroom bulb? Explain why this is a disadvantage. (2)
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(a) Circuit diagram (3 marks):
- Battery connected correctly: 1 mark
- Living room bulb + switch in one parallel branch: 1 mark
- Bedroom bulbs (series or parallel) + switch in another parallel branch: 1 mark
*(Correct solution: Living room branch = bulb + switch in series with each other. Bedroom branch = two bulbs in parallel or series with a second switch. Both branches connected in parallel across the battery.)*
(b) The other bedroom bulb goes out (1). In a series circuit, there is only one path for current; when one bulb blows, the circuit is broken and current stops flowing everywhere in that branch. This is a disadvantage because the remaining bulb will not work until the blown bulb is replaced (1).
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