CSCA Physics and Chemistry Practice: Four Worked Questions

CSCA Physics and Chemistry practice should develop two habits together: choosing the correct scientific model and checking the result against the question's conditions. This guide contains two original Physics questions and two original Chemistry questions, each with a complete solution. They are independent Passumi exercises, not official questions, reconstructed exam content or predictions of a future paper.

The examples cover constant acceleration, series circuits, solution concentration and reaction stoichiometry. These topics fall within the published CSCA syllabuses. They do not cover the entire syllabus: Physics also includes heat, waves, optics and modern physics; Chemistry also includes structure, equilibrium, organic chemistry and experimental skills.

Confirm which science papers your degree requires

Physics and Chemistry requirements depend on the university and program. Do not register for both simply because they appear together in a preparation guide. Check your institution's current subject list, scholarship route and accepted examination language.

The official CSCA introduction lists each science paper as 48 objective multiple-choice questions in 60 minutes, available in Chinese or English. The two papers are separate exams. Use CSCA Physics practice and CSCA Chemistry practice for the subjects you actually need.

Before reading each solution, write the known quantities, the unknown quantity and the equation connecting them. This takes only a few seconds and exposes missing assumptions before you begin calculating.

Physics question 1: Constant acceleration

Original practice question. A cart starts from rest and accelerates uniformly at 2.0 m/s^2 along a straight track for 5.0 s. What distance does it travel?

• A. 10 m
• B. 20 m
• C. 25 m
• D. 50 m

Answer: C, 25 m.

“Starts from rest” gives initial velocity u = 0 m/s. Uniform acceleration means a = 2.0 m/s^2 stays constant. Time is t = 5.0 s. Use s = ut + (1/2)at^2.

Substitution gives s = 0 × 5.0 + (1/2) × 2.0 × 5.0^2 = 25 m. Because the cart moves in one direction throughout the interval, the magnitude of displacement equals the distance traveled.

Check the units: acceleration multiplied by time squared gives (m/s^2) × s^2 = m, so the result has the required length unit.

A second check uses velocity. Final velocity is v = u + at = 10 m/s. For constant acceleration, average velocity is (u + v)/2 = 5.0 m/s. Multiplying this by 5.0 seconds again gives 25 meters.

Option D multiplies final velocity by the entire time. That incorrectly assumes the cart was already traveling at 10 meters per second from the beginning. Remember that “velocity,” “acceleration” and “distance” describe different quantities.

Physics question 2: Current and energy in a series circuit

Original practice question. Two ideal resistors, 4 ohms and 8 ohms, are connected in series across an ideal 12 V supply. How much energy is transferred to the 8-ohm resistor in 30 seconds?

• A. 60 J
• B. 120 J
• C. 240 J
• D. 360 J

Answer: C, 240 J.

For series resistors, total resistance is R = 4 + 8 = 12 ohms. Ohm's law gives circuit current I = V/R = 12/12 = 1 A. The same current flows through both resistors.

Power in the 8-ohm resistor is P = I^2 R = 1^2 × 8 = 8 W. Energy transferred during 30 seconds is E = Pt = 8 × 30 = 240 J.

The unit check is W × s = J, which is appropriate for energy. A watt measures energy transfer per second; it is not itself an amount of energy.

Check the circuit's energy balance. Total power supplied is VI = 12 × 1 = 12 W. The 4-ohm resistor dissipates 4 W and the 8-ohm resistor dissipates 8 W. Their sum is 12 W. Over 30 seconds, 120 J plus 240 J equals the supply's 360 J.

Option D reports energy for the entire circuit. Another common error applies all 12 volts to the 8-ohm resistor; its actual voltage drop is IR = 8 V.

Chemistry question 1: Dilute a solution

Original practice question. A student transfers 25.0 mL of a 0.200 mol/L sodium chloride solution into a volumetric flask, then adds water to a final solution volume of 100.0 mL. What is the final concentration?

• A. 0.0250 mol/L
• B. 0.0500 mol/L
• C. 0.100 mol/L
• D. 0.800 mol/L

Answer: B, 0.0500 mol/L.

Dilution changes the volume but preserves the amount of dissolved sodium chloride, assuming complete transfer and no reaction or loss. Convert the original volume to liters: 25.0 mL = 0.0250 L.

Initial amount is n = cV = 0.200 × 0.0250 = 0.00500 mol. Final volume is 100.0 mL = 0.1000 L, so c = n/V = 0.00500/0.1000 = 0.0500 mol/L.

The units also work: (mol/L) × L = mol for the first calculation, then mol/L for the second. Alternatively, use c1 V1 = c2 V2 with both volumes expressed in the same unit.

The volume increases by a factor of four, so the concentration should decrease to one quarter of its original value. This magnitude check rules out option D immediately.

“Final volume of 100.0 mL” does not mean adding 100.0 mL of water. Confusing these instructions changes the denominator. In laboratory language, making a solution up to the mark refers to the final solution volume.

Chemistry question 2: Use a balanced reaction

Original practice question. A 5.00 g sample of pure calcium carbonate reacts completely with excess hydrochloric acid. Using 100.0 g/mol for the molar mass of calcium carbonate and 44.0 g/mol for carbon dioxide, what mass of carbon dioxide forms?

• A. 1.10 g
• B. 2.20 g
• C. 4.40 g
• D. 5.00 g

Answer: B, 2.20 g.

The balanced equation is CaCO3 + 2HCl -> CaCl2 + H2O + CO2. One mole of calcium carbonate produces one mole of carbon dioxide. “Excess hydrochloric acid” means the acid does not limit the reaction.

Convert the carbonate mass to amount: n(CaCO3) = 5.00/100.0 = 0.0500 mol. Apply the one-to-one ratio to get n(CO2) = 0.0500 mol. Finally, convert to mass: m(CO2) = 0.0500 × 44.0 = 2.20 g.

The unit sequence is g ÷ (g/mol) = mol, followed by mol × (g/mol) = g. The coefficient 2 belongs to hydrochloric acid; it does not double the amount of carbon dioxide.

No gas volume or molar gas volume is needed. Temperature and pressure would matter for a gas-volume question, but they do not change this theoretical mass calculation under the stated complete-reaction assumption.

Review the error, then choose the next exercise

Classify each mistake as a concept error, an equation-selection error, a unit conversion error or a reading error. Redo the problem with the solution hidden and explain every substitution aloud. A correct option without a correct method is still a topic to review.

Continue with Physics practice or Chemistry practice. Passumi currently makes the first 25% of each available paper free. The CSCA hub connects the full subject range, while the exam guide explains the verified November 2026 schedule and registration deadline.

Sources and last checked

Last checked: October 15, 2026. The numerical examples above are original and use explicitly stated assumptions.

• Official CSCA exam introduction: languages, question counts and durations.
• Official CSCA preparation resources: subject syllabuses and official samples.
• GDUFS reproduction of the 2025-edition syllabuses: mechanics, circuits, concentration and mole calculations. Its historical scheduling details are not used here.