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P4 General Studies: Plant Growth and Photosynthesis (Paper 3 (challenge))
Tutor Prep Guide · the three raw materials for photosynthesis, chlorophyll and the oxygen given out, roots taking up water and the stem carrying it, and how photosynthesis differs from respiration
P4 General Studies: Plant Growth and Photosynthesis (Paper 3 (challenge))
Paper three works on experiment reasoning and two step sums: the dark leaf test, net photosynthesis, bubble counts and greenhouse carbon dioxide.
Direct answers For experiment questions, write what was changed, then what was measured, and only then the conclusion.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 20 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: P4 General Studies: Plant Growth and Photosynthesis |
| Level | parts of a closed circuit, conductors against insulators, series against parallel, adding up battery voltage, and electrical safety |
02 Questions (10 items)
- FoundationA leaf kept in the dark for a day shows no blue-black colour with iodine. What does that show?
- FoundationIn an hour a leaf makes 18 units of food by photosynthesis and uses 6 units in respiration. What is the net gain?
- FoundationWhy does carbon dioxide rise in a bedroom with plants at night?
- IntermediateA water plant gives 18 bubbles a minute in strong light and 12 in weak light. What is the percentage increase?
- IntermediateThree hundred sixty of 480 seedlings flower. What share is that?
- IntermediateGreenhouse carbon dioxide goes from 400 ppm to 600 ppm. What is the percentage increase?
- ChallengeThirty-six of 45 fruit trees bear fruit. What share is that?
- ChallengeWhich part carries water from the root up to the leaves?
- ChallengeWhat good does transpiration do for a plant?
- Error redoError clinic: roots can make food too because leaves are not the only place. Is that right?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Without light the leaf made no starch. | Iodine turns blue-black with starch; no colour means no new starch, which proves light is needed. |
| 2 | 12 units. | Eighteen minus six gives 12 units; this net figure is what the plant can actually store. |
| 3 | There is no light at night, so photosynthesis stops and only respiration adds carbon dioxide. | Respiration never stops; at night nothing uses up the carbon dioxide, so it builds up. |
| 4 | 50.0 percentage points. | Eighteen minus twelve is six; six over twelve times one hundred gives 50.0 percentage points. |
| 5 | 75.0 percentage points. | Three hundred sixty over 480 times one hundred gives 75.0 percentage points. |
| 6 | 50.0 percentage points. | Six hundred minus 400 is 200 ppm; 200 over 400 times one hundred gives 50.0 percentage points. |
| 7 | 80.0 percentage points. | Thirty-six over 45 times one hundred gives 80.0 percentage points. |
| 8 | The stem, whose vessels carry water and minerals upwards. | The stem is the pipeline that lifts water from the roots to the leaves for photosynthesis and transpiration. |
| 9 | It helps pull water and minerals up and cools the leaf in hot weather. | Water lost through the stomata pulls the water column upward and carries heat away at the same time. |
| 10 | No. | Photosynthesis needs chlorophyll; roots have none, so they absorb water and minerals but make no food. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
Paper four clears the conductor, insulator and battery direction misconceptions.Tutor Registration →
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