Secondary 4 Combined Science Physics Language Use Quiz

Secondary 4 Combined Science Physics Quiz – Language Use

Answer Key

Section A: Scientific Terminology and Definitions

1. Acceleration is the rate of change of velocity with respect to time. [2]
Marking notes: Award 1 mark for "rate of change of velocity" and 1 mark for mentioning "per unit time" or "with time." Accept "change in velocity per second."

2. Thermal equilibrium is the state in which two objects in thermal contact reach the same temperature, and there is no net transfer of thermal energy between them. [2]
Marking notes: Award 1 mark for "same temperature" and 1 mark for "no net heat/thermal energy transfer."

3. Refraction of light is the bending of light as it passes from one transparent medium to another due to a change in its speed. [2]
Marking notes: Award 1 mark for "bending of light" and 1 mark for "change in speed / change of medium."

4. The electromotive force (e.m.f.) of a cell is the amount of energy (work done) supplied by the cell per unit charge to drive charge around a complete circuit. [2]
Marking notes: Award 1 mark for "energy supplied per unit charge" and 1 mark for "by the cell / battery." Accept "work done per coulomb."

5. Pressure is defined as the force acting per unit area on a surface. [2]
Marking notes: Award 1 mark for "force per unit area" and 1 mark for correct formula reference or "acting on a surface." Accept p = F/A.

Section B: Using Scientific Language in Context

6. [3]

• The particles at the heated end gain kinetic energy and vibrate more vigorously. [1]
• These particles collide with neighbouring particles, transferring kinetic energy along the rod. [1]
• This process continues until thermal energy is conducted along the entire rod. [1]
  Marking notes: Must refer to particles gaining kinetic energy, collisions/interactions between particles, and transfer along the rod. Award 1 mark for each valid point.

7.
(a) The speed of the light decreases. [1]
Marking notes: Must say "decreases" or "slows down." Do not accept "stops" or "increases."

(b) Light slows down when entering the glass (a denser medium). Because one side of the wavefront enters the glass before the other, the wave changes direction, bending towards the normal. [2]
Marking notes: Award 1 mark for stating that light slows down in glass, and 1 mark for explaining the change in direction (bending towards normal). Accept reference to change in speed causing change in direction.

8. [3]

• The statement is incorrect because charge is conserved in a circuit. [1]
• Current is the rate of flow of charge; the same charge flows through every component in a series circuit. [1]
• The current is the same at all points in a series circuit — it is not "used up." [1]
  Marking notes: Award 1 mark for stating the statement is wrong, 1 mark for conservation of charge / same current, and 1 mark for explaining that current is the same throughout a series circuit.

9. [3]

• The object distance (30 cm) is greater than twice the focal length (2 × 10 = 20 cm), so the image is:
  • Real [1]
  • Inverted [1]
  • Diminished (smaller than the object) [1]
    Marking notes: Award 1 mark for each correct property. If the student incorrectly identifies the image as virtual, award 0 for that part.

10. [3]

• I disagree with the student's statement. [1]
• At the highest point, the velocity is momentarily zero, but the force of gravity (weight) still acts on the ball. [1]
• According to Newton's First Law, a resultant force (gravity) causes the ball to accelerate downwards, which is why it does not remain at rest. [1]
  Marking notes: Award 1 mark for disagreeing, 1 mark for stating gravity still acts, and 1 mark for linking to Newton's First Law or resultant force causing acceleration.

Section C: Interpreting and Communicating Physics Information

11.
(a) The car is accelerating between t = 0 s and t = 4 s. [1]
Marking notes: Accept "0 to 4 seconds" or "0–4 s."

(b) Acceleration = change in velocity ÷ change in time
= (12 − 0) ÷ (4 − 0)
= 12 ÷ 4
= 3 m/s² [2]
Marking notes: Award 1 mark for correct formula/substitution and 1 mark for correct answer with unit. Accept 3.0 m/s².

(c) Between t = 6 s and t = 10 s, the car is decelerating (slowing down) at a constant rate from 12 m/s to 6 m/s. [1]
Marking notes: Accept "decelerating" or "slowing down." Must indicate the speed is decreasing.

12.
(a) [3]

• The molecules with the highest kinetic energy escape from the surface during evaporation. [1]
• This means the average kinetic energy of the remaining water molecules decreases. [1]
• Since temperature is a measure of the average kinetic energy of particles, the temperature of the remaining water decreases. [1]
  Marking notes: Award 1 mark for each logical step: highest-energy molecules escape → average KE drops → temperature falls.

(b) Evaporation occurs at any temperature, while boiling occurs only at a specific temperature (the boiling point). [1]
Marking notes: Accept any valid difference, e.g., "evaporation occurs only at the surface; boiling occurs throughout the liquid."

13.
(a) The remaining bulb goes off / there is no brightness. [1]
Marking notes: In a series circuit, removing one component breaks the circuit.

(b) In a series circuit, there is only one path for current to flow. When one bulb is removed, the circuit is broken (open circuit), so no current flows through the remaining bulb. [2]
Marking notes: Award 1 mark for "only one path" and 1 mark for "circuit is broken / no current flows."

(c) Each bulb in the parallel circuit is brighter than in the series circuit. [1]
Marking notes: In parallel, each bulb receives the full e.m.f. of the battery, so more current flows through each bulb compared to the series arrangement.

14.
(a) The angle of reflection is 35°. [1]
Marking notes: The angle of reflection equals the angle of incidence.

(b) [3]
The diagram should show:

• A straight line representing the mirror (with shading/hatching on the back). [1]
• A normal drawn perpendicular to the mirror surface at the point of incidence. [1]
• An incident ray at 35° to the normal on one side, and a reflected ray at 35° to the normal on the other side, both clearly labelled with the angles marked. [1]
  Marking notes: Award 1 mark for each correctly drawn and labelled element. The angles must be measured from the normal, not the mirror surface.

15.
(a) Weight = mass × gravitational field strength
= 5.0 × 10
= 50 N [1]
Marking notes: Award 1 mark for correct answer with unit.

(b) Area = 0.10 × 0.20 = 0.020 m²
Pressure = Force ÷ Area
= 50 ÷ 0.020
= 2500 Pa (or 2500 N/m²) [2]
Marking notes: Award 1 mark for correct area calculation and 1 mark for correct final answer with unit.

(c) The pressure increases because the contact area is smaller while the force (weight) remains the same. Since pressure = force / area, a smaller area results in greater pressure. [1]
Marking notes: Must state that pressure increases and give a reason involving area decreasing.

Section D: Extended Response – Explaining Physics Concepts

16. [4]

• Both the metal handle and the wooden door are at the same room temperature. [1]
• Metal has a much higher thermal conductivity than wood. [1]
• When you touch the metal handle, thermal energy is conducted rapidly away from your hand into the metal, making your hand feel cold. [1]
• Wood is a poor conductor, so thermal energy is transferred away from your hand much more slowly, and it does not feel as cold. [1]
  Marking notes: Award 1 mark for each valid point. Must compare thermal conductivity of metal vs. wood and link to rate of thermal energy transfer from the hand.

17.
(a) Refraction. [1]
Marking notes: Accept "refraction of light."

(b) [3]

• Light travels at different speeds in water and in air. Light travels slower in water (a denser medium) than in air. [1]
• When light from the submerged part of the straw passes from water into air, it speeds up and bends away from the normal. [1]
• The brain assumes light travels in straight lines, so the submerged part of the straw appears to be at a different position, making the straw look bent at the surface. [1]
  Marking notes: Award 1 mark for different speeds in different media, 1 mark for bending away from normal, and 1 mark for the brain's interpretation / apparent shift in position.

18. [4]
Apparatus: A power supply (battery), an ammeter, a voltmeter, a length of resistance wire (e.g., nichrome), a beaker of water, a Bunsen burner (or hot water bath), connecting wires, and a thermometer. [1]
Marking notes: Award 1 mark for listing appropriate apparatus.

Procedure:

• Set up a circuit with the resistance wire connected in series with the ammeter and power supply; connect the voltmeter across the wire. [1]
• Record the ammeter and voltmeter readings at room temperature.
• Heat the resistance wire by placing it in hot water (or using a Bunsen burner).
• Record the new ammeter and voltmeter readings at the higher temperature.

Observations: As the temperature increases, the ammeter reading decreases (current decreases), while the voltage may stay the same or change slightly. The resistance (V/I) increases. [1]
Marking notes: Award 1 mark for describing a valid procedure with heating and measurement.

Conclusion: The resistance of a metallic conductor increases with temperature because the metal ions vibrate more at higher temperatures, causing more frequent collisions with the flowing electrons, which impedes the flow of charge. [1]
Marking notes: Award 1 mark for the conclusion linking increased temperature to increased resistance, with a brief explanation.

19. [4]

• Before braking, the car is moving at a constant velocity. According to Newton's First Law, the forces on the car are balanced (driving force equals resistive forces). [1]
• When the brakes are applied, a friction force is exerted by the brake pads on the wheels, opposing the motion of the car. [1]
• This friction force is an unbalanced (resultant) force acting in the opposite direction to the car's motion. [1]
• According to Newton's First Law, an unbalanced force causes the car to decelerate (slow down) until it comes to rest. [1]
  Marking notes: Award 1 mark for each valid point. Must reference Newton's First Law, friction from brakes, unbalanced force, and deceleration.

20.
(a) The total current from the battery is equal to the sum of the currents in each branch. [1]
Marking notes: Accept "I_total = I₁ + I₂" or equivalent wording.

(b)(i) [2]
Current through the 6 Ω resistor:
I₁ = V / R₁ = 12 / 6 = 2.0 A [1]

Current through the 12 Ω resistor:
I₂ = V / R₂ = 12 / 12 = 1.0 A [1]
Marking notes: Award 1 mark for each correct current calculation with unit.

(b)(ii) Total current = I₁ + I₂ = 2.0 + 1.0 = 3.0 A [1]
Marking notes: Award 1 mark for correct total current. Follow through from part (b)(i) if values were incorrect but method is correct.