A Levels Biology (9700)•9700/13/M/J/24
Explanation
Surface Area to Volume Ratio Affects Diffusion Time
Steps:
- For cubes, SA/V = 6/side length (SA=6s², V=s³).
- Block 1 (3 mm): 6/3 = 2.0:1.0.
- Block 2 (8 mm): 6/8 = 0.75:1.0.
- Block 3 (11 mm): 6/11 ≈ 0.55:1.0.
- Time to turn yellow increases as SA/V decreases, since diffusion is slower in larger blocks.
Why C is correct:
- Matches exact SA/V ratios and times (4 min for highest ratio, increasing to 13 min for lowest), per inverse relationship in diffusion.
Why the others are wrong:
- A: Ratios incorrect (underestimates for small block, wrong for large).
- B: Ratios correct but times reversed (fastest for largest block).
- D: Ratios correct but time for smallest block wrong (3 min vs. 4 min).
Final answer: C
Topic: Movement into and out of cells
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