Primary General Studies: Air, Combustion And Rusting (Paper 2 (intermediate))

Primary General Studies: Air, Combustion and Rusting (Paper 2 (intermediate))

2026-11-13

Tutor Prep Guide · Food chains, producers and consumers, energy flow and ecological balance

Primary General Studies: Air, Combustion and Rusting (Paper 2 (intermediate))

Paper two adds the uses of nitrogen and carbon dioxide, controlled experiment design and rate comparisons, for pupils who already know the basics.

Direct answers　State clearly that only one variable changes in a controlled experiment, and divide the longer time by the shorter one in a rate question.

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: Primary General Studies: Air, Combustion and Rusting
Level	parts of a closed circuit, conductors against insulators, series against parallel, adding up battery voltage, and electrical safety

02　Questions (10 items)

FoundationWhy is carbon dioxide often used to put out fires?
FoundationWhy is nitrogen filled into a packet of crisps?
FoundationIs rusting a chemical change or a physical change?
IntermediateAbout how many litres of oxygen are in 2 000 litres of air?
IntermediateEach iron rod needs 15 mL of anti rust oil. How much is needed for 8 rods?
IntermediateA 50 g block of iron weighs 55 g after rusting. What percentage of the original mass is the extra 5 g?
ChallengeThree bottles: A holds dry air, B holds boiled distilled water and is sealed, C holds tap water open to the air. Which one rusts after 5 days and why?
ChallengeA sealed 800 mL bottle holds 168 mL of oxygen and a candle uses 12 mL a minute. How long can it burn?
ChallengeThe same kind of nail rusts in 3 days in salt water and in 12 days in fresh water. How many times faster is salt water?
Error redoA classmate says a nail sealed in boiled distilled water still rusts. What is wrong?

03　Answers and one-line notes

#	Answer	One-line note
1	It is heavier than air, so it covers the flame and cuts off the oxygen.	Burning cannot continue without oxygen, so the carbon dioxide from a fire extinguisher puts the fire out.
2	It pushes the oxygen out so the food does not oxidise and spoil.	Nitrogen is unreactive and does not react with food, so it keeps the food fresh for longer.
3	It is a chemical change, because a new substance, rust, is formed.	Rust behaves quite differently from iron, and forming a new substance makes it a chemical change.
4	About 420 litres.	2 000 times 0.21 is 420.
5	120 mL is needed.	15 times 8 is 120.
6	It is 10 per cent.	5 divided by 50 is 0.1, which is 10 per cent.
7	Only C rusts, because A has no water and B has no oxygen.	Rusting needs both oxygen and water, so only C has the two conditions together.
8	It can burn for 14 minutes.	168 divided by 12 is 14.
9	It is 4 times faster.	12 divided by 3 is 4, so salt water speeds rusting up a lot.
10	Boiling drives the dissolved oxygen out, and sealing keeps new oxygen away, so the nail does not rust.	Rusting needs oxygen, so remove that condition and no rust appears.

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.

Then try paper three, using voltage and current to work out power and resistance.Tutor Registration →

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.