Skip to content
IGCSEBiology
Trial Class

Original practice · 5 questions · 15 marks · about 17 minutes

Factors Affecting Diffusion Rate Practice Questions

Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.

These questions test your ability to explain and predict how changing conditions affect the rate of diffusion in biological systems.

Before you open the answers

  • Attempt every question without notes.
  • Show working for calculations and write complete biological statements.
  • Use the suggested time as a guide, not a strict limit on the first attempt.

These are original practice questions. They do not reproduce an official Cambridge paper or official mark scheme.

  1. Question 1

    Paper 4 Both 3 marks Difficulty 3/5

    Explain why increasing the temperature increases the rate of diffusion.

    Show model answer and marking guidance
    1. Higher temperature gives molecules more kinetic energy.
    2. Molecules move faster / more rapidly.
    3. More molecules cross the membrane per unit time / more frequent collisions.

  2. Question 2

    Paper 4 Extended 4 marks Difficulty 4/5

    Two cubes of agar jelly containing indicator are placed in acid. Cube A is 1 cm³ and Cube B is 3 cm³. Predict which cube will change colour completely first, and explain why.

    Show model answer and marking guidance
    1. Cube A will change colour first.
    2. Cube A has a larger surface area to volume ratio.
    3. The diffusion distance to the centre is shorter in Cube A.
    4. Acid reaches the centre faster in the smaller cube.

  3. Question 3

    Paper 2 Core 2 marks Difficulty 2/5

    State what is meant by a "concentration gradient".

    Show model answer and marking guidance
    1. A difference in concentration between two areas / regions.
    2. Molecules move from the higher concentration to the lower concentration.

  4. Question 4

    Paper 4 Extended 3 marks Difficulty 3/5

    Explain why a thin gas exchange surface increases the rate of diffusion.

    Show model answer and marking guidance
    1. Thinner surface means shorter diffusion distance / pathway.
    2. Molecules take less time to cross.
    3. Rate of diffusion is inversely proportional to thickness / distance.

  5. Question 5

    Paper 4 Both 3 marks Difficulty 3/5

    Blood flow through capillaries around the alveoli helps maintain a high rate of gas exchange. Explain how.

    Show model answer and marking guidance
    1. Blood carries oxygen away from the alveoli.
    2. This keeps the oxygen concentration low in the blood / near the alveolar surface.
    3. Maintains a steep concentration gradient for oxygen diffusion from alveolus to blood.

Mark the set consistently

Award a point only when the idea is clearly present in the written answer. Correct any missed point in a complete sentence, then test the same skill on a different question several days later.

Review the related teaching