Secondary 4 Combined Science Physics Argument Evaluation Quiz

Secondary 4 Combined Science Physics Quiz - Argument Evaluation

Answer Key and Marking Scheme

Total Marks: 40

Section A: Identifying Claims and Evidence (Questions 1–5)

1. (a) Claim: Smoother surfaces reduce friction, allowing objects to travel greater distances. / The ball rolled further because the smooth table has less friction. [1]

(b) Evidence: The ball rolled further on the smooth table compared to a rough surface (implied observation). [1]

2. (a) Claim: The sports car is the fastest-accelerating car in its class (0 to 60 km/h in 3.2 seconds). [1]

(b) Any two of the following: [2]

• The acceleration values of other cars in the same class for comparison
• The conditions under which the test was conducted (road surface, weather, load)
• Whether the test was conducted by an independent body
• The definition of "its class" (what cars are being compared)
• Whether the 3.2 seconds is an average or best-case result

3. (a) Claim: Increasing the mass of the trolley decreases its acceleration, and this proves Newton's Second Law (F = ma). [1] Evidence: Experimental results showing that greater mass led to smaller acceleration. [1]

(b) The reasoning is partially sound but incomplete. The student correctly identifies the inverse relationship between mass and acceleration at constant force, which is consistent with F = ma. However, "proving" a law requires extensive evidence across many conditions; a single experiment supports but does not prove the law. [1]

4. (a) Conclusion: Switching to electric vehicles reduces air pollution. [1]

(b) Alternative explanation: Cities with more electric vehicles may also have stricter emission regulations, more green spaces, better public transport, or different industrial activity levels that contribute to cleaner air. The correlation does not necessarily mean causation. [1]

5. (a) Flaw: The student assumes that because copper is used in school wiring, it must be the best conductor. This is circular reasoning — the use of copper does not by itself prove it is the best; it may be chosen for cost, availability, or safety reasons. [1]

(b) Stronger evidence: Experimental data comparing the electrical conductivity of copper with other metals (e.g., silver, aluminium, gold) under controlled conditions, showing copper has lower resistivity / higher conductivity. [1]

Section B: Evaluating Arguments (Questions 6–14)

6. The argument is scientifically valid. [1] In a vacuum, there is no air resistance, so the only force acting on both objects is gravitational force (weight = mg). [1] Although the steel ball experiences a greater gravitational force due to its larger mass, its greater mass also means greater inertia. From F = ma, we get a = F/m = mg/m = g, so both objects accelerate at the same rate (g ≈ 9.81 m/s²). [1] This was famously demonstrated on the Moon during the Apollo 15 mission. [Total: 3]

7. (a) Principle: Newton's Third Law of Motion — for every action, there is an equal and opposite reaction. [1]

(b) Flaw: The student incorrectly states that the action-reaction forces "cancel out." Newton's Third Law forces act on different objects (the push on the box acts on the box; the reaction push acts on the student), so they cannot cancel each other. Forces can only cancel if they act on the same object. The box does not move until the applied force exceeds the maximum static friction force acting on the box. [2]

8. The argument is partially correct but has limitations. [1] It is correct that insulation traps air and that air is a poor conductor of heat, reducing heat transfer by conduction. [1] However, the claim that "the thicker the insulation, the warmer the house" has limitations: beyond a certain thickness, additional insulation provides diminishing returns; insulation also works by reducing convection (trapped air pockets prevent convection currents); and if insulation gets compressed or wet, its effectiveness decreases. Additionally, heat can still be lost through radiation and through gaps in insulation. [1] [Total: 3]

9. (a) The conclusion is partially valid — measuring current at two points in a series circuit and finding the same value is consistent with Kirchhoff's Current Law, but two measurements alone are limited evidence. [1]

(b) Additional evidence: Measuring the current at multiple points throughout the circuit (before and after each component), or testing with different circuit configurations (different numbers of bulbs, different resistances), would strengthen the conclusion. [1]

10. (a) Claim: The solar panels have a 95% efficiency rate and are the most efficient available. [1]

(b) Any two of the following: [2]

• How was the efficiency measured and by whom?
• What is the efficiency of other commercially available solar panels for comparison?
• Under what conditions (light intensity, angle, temperature) was the 95% achieved?
• Is this a laboratory result or real-world performance?
• What is the definition of "efficiency" being used (electrical output vs solar energy input)?

11. (a) The reasoning is scientifically sound in its conclusion. [1]

(b) Sound is a mechanical wave that requires a medium (particles) to propagate. In a vacuum, there are no particles to transmit vibrations, so sound cannot travel. The reference to space is appropriate as space is effectively a vacuum. However, the phrase "no one can hear you scream" is a pop-culture reference rather than scientific evidence; a stronger argument would reference experimental evidence such as the bell-jar experiment, where a ringing bell becomes inaudible as air is removed from the jar. [2]

12. (a) Claim: Human activity is causing global warming (as evidenced by Singapore's 1.5°C temperature increase over 50 years). [1]

(b) The evidence is insufficient to conclusively support the claim. [1] While the temperature increase is consistent with global warming, correlation alone does not prove causation by human activity. Other factors such as natural climate variability, urban heat island effect (Singapore's urbanisation), and changes in land use could also contribute to the observed temperature rise. To strengthen the claim, evidence linking greenhouse gas emissions to temperature changes, climate modelling data, and global (not just local) temperature trends would be needed. [1] [Total: 3]

13. The student's error is concluding that light travels faster in glass because it bends towards the normal. [1] When light bends towards the normal, it is entering a denser medium and actually slows down. The refractive index of glass is greater than that of air, meaning light travels slower in glass. The bending towards the normal is a consequence of this decrease in speed, not an increase. [1] [Total: 2]

14. The argument has significant logical weaknesses. [1] While it is true that modern reactors have safety systems and that major accidents are rare, claiming nuclear power is "completely safe" is an overstatement — no technology is completely without risk. [1] The argument commits the fallacy of appealing to limited evidence: few accidents does not mean zero risk. It also ignores other concerns such as radioactive waste disposal, the consequences of rare but catastrophic accidents (e.g., Fukushima, Chernobyl), and the long-term environmental impact. A stronger argument would acknowledge both the safety record and the remaining risks. [1] [Total: 3]

Section C: Constructing and Analysing Arguments (Questions 15–20)

15. (a) Student B is correct. [1]

(b) According to Newton's law of universal gravitation, the gravitational force on an object is F = mg. From Newton's Second Law, F = ma, so ma = mg, giving a = g. The mass cancels out, meaning all objects experience the same gravitational acceleration (approximately 9.81 m/s² near Earth's surface) regardless of their mass, provided air resistance is negligible. [2]

(c) Student A's observation may appear true in real-world conditions where air resistance is significant. Objects with large surface area relative to their mass (e.g., a feather, a piece of paper) experience greater air resistance, which opposes gravity and reduces their acceleration. In air, a heavy compact object like a steel ball will fall faster than a light, spread-out object like a feather. [1]

16. (a) Any two of the following: [2]

• Independent test results showing the percentage heat loss reduction
• The conditions under which the 70% reduction was measured (temperature difference, window size, wind conditions)
• Comparison data with standard single-glazed and other double-glazed windows
• The specific design features of the window (gap width, gas fill, coating type)

(b) Double-glazed windows reduce heat transfer through: [2]

• Conduction: The air (or inert gas) trapped between the two panes is a poor conductor of heat, reducing heat transfer by conduction compared to a single pane.
• Convection: The narrow gap between the panes limits convection currents, reducing heat transfer by convection. (If the gap is too wide, convection currents can form and reduce effectiveness.)

17. (a) Any two of the following controlled variables: [1]

• Cross-sectional area (thickness/diameter) of the wire
• Temperature of the wire
• Type/material of the wire
• Voltage applied across the wire

(b) The graph of resistance against length must show a straight line passing through the origin (0, 0) for the conclusion of direct proportionality to be valid. [1]

(c) The criticism has some merit but is not entirely valid for this specific conclusion. Using one type of wire is appropriate when investigating the relationship between length and resistance, as the material is a controlled variable. However, testing multiple types of wire would strengthen the generalisability of the conclusion — it would show that the relationship holds across different materials, not just one. For the specific claim about length and resistance, the single-material approach is acceptable. [1]

18. (a) Strength: The argument cites a specific study with quantitative data (40% less CO₂), which provides measurable evidence. It also correctly identifies that electric cars produce zero tailpipe emissions during operation. [1]

(b) Weakness: The argument only considers emissions during driving and ignores emissions from electricity generation (if the electricity comes from fossil fuels), battery manufacturing, and battery disposal/recycling. The "zero emissions" claim is misleading when considering the full lifecycle. [1]

(c) Additional information: The source of electricity used to charge the electric car (renewable vs fossil fuel), the total lifecycle emissions including manufacturing and disposal, or the methodology and independence of the cited study. [1]

19. (a) Error: The student incorrectly claims the metal spoon is at a lower temperature than the wood. Both spoons are at the same room temperature. [1]

(b) Correct explanation: Metal is a good conductor of heat, while wood is a poor conductor (insulator). When you touch the metal spoon, heat is rapidly conducted away from your hand into the spoon, making your skin temperature drop quickly, which your nerves interpret as "cold." With the wooden spoon, heat is conducted away slowly, so your skin temperature does not drop as much, and it feels less cold (or closer to room temperature). The sensation of coldness reflects the rate of heat transfer, not the actual temperature. [2]

20. (a) The argument is incorrect. [1]

(b) According to Newton's First Law, an object at rest would have zero net force only if it remains at rest. However, the ball at the highest point is only momentarily at rest — it immediately begins to accelerate downwards. According to Newton's Second Law, since the ball is accelerating downwards (changing velocity from zero to downward), there must be a net downward force acting on it. The net force is the gravitational force (weight) acting on the ball, which is present throughout the motion, including at the highest point. [2]

(c) The net force on the ball at the highest point is equal to its weight (mg), acting vertically downwards. [1] (Magnitude: mg, where m is the mass of the ball and g ≈ 9.81 m/s²)

End of Answer Key