P3 General Studies: Dissolving And Separation (Paper 2 (intermediate))

P3 General Studies: Dissolving and Separation (Paper 2 (intermediate))

2026-11-13

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P3 General Studies: Dissolving and Separation (Paper 2 (intermediate))

Paper two moves on to separation methods and solubility ratios: evaporation, filtration, magnets and distillation each have a use, with solubility scaled by the mass of water and dilution recalculated.

Direct answers　For a separation item ask first which part must be kept; for a solubility item first convert everything to per 100 g of water.

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: P3 General Studies: Dissolving and Separation
Level	parts of a closed circuit, conductors against insulators, series against parallel, adding up battery voltage, and electrical safety

02　Questions (10 items)

FoundationSalt solution is left in the sunshine and the water slowly evaporates. What is left at the bottom?
FoundationWhat is the quickest way to separate iron nails from sand?
FoundationWhat kind of substance stays on the filter paper during filtration?
Intermediate15 g of salt is dissolved in 60 g of water, giving 75 g of solution. What percentage of the solution is salt?
IntermediateAt 20 degrees Celsius, 100 g of water dissolves at most 36 g of salt. How much salt can 150 g of water dissolve?
Intermediate250 g of salt solution is evaporated to dryness and gives 25 g of salt. What percentage of the original solution was salt?
Challenge500 g of sugar solution contains 60 g of sugar. After adding 100 g of water, what percentage of the solution is sugar?
ChallengeWhich separation method gives back both the salt and the fresh water from sea water?
ChallengeA salt dissolves 36 g per 100 g of water at 20 degrees and 39 g at 60 degrees. How much more salt dissolves in 200 g of water at 60 degrees than at 20 degrees?
Error redoA classmate filters salt solution to collect the salt, but the filtrate is still salty. Why?

03　Answers and one-line notes

#	Answer	One-line note
1	Salt crystals.	The water leaves as vapour and the salt stays behind as crystals.
2	Use a magnet to pick up the nails.	Iron is attracted by a magnet and sand is not, so they can be separated.
3	An undissolved solid, such as sand.	Only undissolved solids are trapped by the paper; dissolved substances pass through with the water.
4	20.0 percent	Fifteen divided by seventy-five times one hundred gives 20.0 percent.
5	54.0 g	Thirty-six times one point five equals 54.0.
6	10.0 percent	Twenty-five divided by two hundred and fifty times one hundred gives 10.0 percent.
7	10.0 percent	The sugar is still 60 g but the solution is now 600 g, so sixty divided by six hundred gives 10.0 percent.
8	Distillation: evaporate the water and then condense it.	Evaporation alone leaves only the salt; condensing the vapour recovers the water as well.
9	6 g	Three more grams per 100 g of water means six more grams in 200 g of water.
10	The salt is dissolved, so its particles pass through the paper; evaporation is needed to recover it.	Filtration only traps undissolved solids; dissolved salt flows through with the water.

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 →

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