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Primary General Studies, People and the Environment, Paper 4: water cycle, energy and carbon
Primary General Studies, People and the Environment, Paper 4: water cycle, energy and carbon
Ten items on evaporation and the water cycle, renewable energy, greenhouse gases, the waste hierarchy, electricity bills, solar output, landfill share, LED savings, tree offset and battery recycling.
Focus Evaporation, condensation and rain make the water cycle; solar, wind and water are renewable; carbon dioxide is the main greenhouse gas; reducing comes before reusing and recycling; the bill is units times price; units are kilowatts times hours; landfill mass is total times share; savings are the power gap times hours; trees offset part of the carbon; batteries need separate recycling.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 25 |
| Difficulty mix | Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1 |
| Chapter | Chapter: Primary General Studies: People and the Environment |
| Level | P4 to P6 |
02 Questions (10 items)
- FoundationSea water turns into water vapour under the sun. What is this process called?
- FoundationWhich of these is a renewable energy source: coal, solar energy or oil?
- FoundationWhich greenhouse gas causes most global warming?
- FoundationWhat is the best order for dealing with waste?
- IntermediateA household uses 12 units of electricity a day. How much is used in 30 days, and what is the bill at $1.2 per unit?
- IntermediateA 400 W solar panel is fully lit for 5 hours. How many units does it generate?
- IntermediateHong Kong produces about 15 000 tonnes of solid waste a day and 60 per cent goes to landfill. How many tonnes is that?
- ChallengeA 9 W LED bulb replaces a 60 W filament bulb and is used 5 hours a day. How many units are saved in a year of 365 days?
- ChallengeOne tree absorbs about 20 kg of carbon dioxide a year and a household emits 4 800 kg a year. How many trees would offset it?
- Error redoA classmate says used batteries can go straight into the ordinary rubbish bin. Is this correct?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Evaporation. | The vapour rises, cools and condenses into droplets that form clouds and fall back as rain. |
| 2 | Solar energy. | Coal and oil are fossil fuels that cannot be replaced, while solar, wind and water keep renewing. |
| 3 | Carbon dioxide. | Burning coal, oil and gas releases large amounts of carbon dioxide, which traps more heat. |
| 4 | Reduce first, then reuse, and recycle last. | Recycling still uses energy, so not making the waste at all beats recycling it. |
| 5 | 360 units, so the bill is $432. | Multiply the daily use by the days to get the total, then by the price per unit for the bill. |
| 6 | 2 units, that is 2 kWh. | Units are kilowatts times hours, so 0.4 times 5 is 2 units. |
| 7 | That is 9 000 tonnes. | 15 000 times 60 per cent is 9 000 tonnes, and the rest is recycled or reprocessed. |
| 8 | About 93.1 units of electricity. | The saving is 51 W, times 5 hours and 365 days, divided by 1 000, so about 93.1 units. |
| 9 | It would take 240 trees. | 4 800 divided by 20 is 240 trees, and cutting electricity use works faster than planting. |
| 10 | No. Batteries contain heavy metals and belong at a collection point, or they pollute soil and water. | A single button cell can contaminate a large volume of water, so batteries must be recycled separately. |
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.
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Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.
