S2 Science: Separating Mixtures (Paper 2 (intermediate))

2026-11-14

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Tutor Prep Guide · Filtration, distillation, fractional distillation and chromatography with Rf calculations

This paper practises comparison and calculation: mixtures against compounds, filtrate against distillate, the direction of cooling water, boiling point differences and Rf values.

Direct answers　In comparison questions state both the property used and the apparatus involved, and only then is the answer complete. An Rf calculation must use the solvent front distance measured on the same piece of paper, never a value from another sheet.

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: S2 Science: Separating Mixtures
Level	S2

02　Questions (10 items)

FoundationWhat is the key difference between a mixture and a compound?
FoundationWhich is a pure substance, distilled water or sea water?
FoundationWhat is the liquid that passes through the filter paper called?
IntermediateA pigment spot moves 2.4 cm and the solvent front moves 6.0 cm. What is the Rf value?
IntermediateAt which end should cooling water enter the condenser?
IntermediateWhy can distillation separate ethanol from water?
ChallengeDistilling 500 cm³ of a mixture recovers eighty percent. What volume of distillate is collected?
ChallengeIn chromatography, is a pigment with a larger Rf value adsorbed more strongly or more weakly?
ChallengeTwo liquids differ in boiling point by only 5 °C. Is simple distillation or fractional distillation better?
Error redoA student claims an Rf value of 1.4. What is the correct range?

03　Answers and one-line notes

#	Answer	One-line note
1	Each component of a mixture keeps its own properties and can be separated by physical means	A compound is formed by chemical reaction with a fixed ratio and cannot be split by filtering or distilling.
2	Distilled water	Distilled water contains only water particles, while sea water holds dissolved salts and is a mixture.
3	The filtrate	The filtrate may still be a solution: filtering sand from salt water leaves salt water behind.
4	0.40	Two point four divided by six point zero gives 0.40.
5	At the lower end, leaving from the upper end	Counter current cooling keeps the biggest temperature difference along the condenser and condenses vapour best.
6	Ethanol boils near 78 °C, below the 100 °C of water, so it vaporises first	On heating to about 78 °C the ethanol turns to vapour first and is condensed and collected.
7	400 cm³	Five hundred times zero point eight equals four hundred, so 400 cm³ is collected.
8	More weakly	Weak adsorption lets the solvent carry it further, which gives the larger Rf value.
9	Fractional distillation	A fractionating column allows repeated vaporisation and condensation, which separates liquids with close boiling points.
10	An Rf value always lies between 0 and 1	A spot can travel at most as far as the solvent front, so the largest possible Rf is 1.

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.

For separation questions ask two things: whether each component dissolves in water, and whether their boiling points or adsorption differ.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.