IMO Practice Test — Methods of Separation in Everyday Life
6 Questions • 15 min • Olympiad level
15:00
Question 1 of 6
A mixture of iron filings, sand and salt is to be fully separated. The BEST first step is to:
Use a magnet to remove the iron filings
Add more salt
Heat everything at once
Throw it away
Explanation: A magnet quickly removes the magnetic iron filings first, using a property of the material.
Question 2 of 6
After the iron is removed, water is added to the sand-and-salt mixture. Filtering it gives:
Sand as residue and salt water as filtrate
Salt as residue and sand as filtrate
Only iron
Nothing
Explanation: Insoluble sand is trapped as residue; the dissolved salt passes through in the filtrate.
Question 3 of 6
Winnowing works because grain and husk differ mainly in their:
Weight
Colour
Taste
Smell
Explanation: The light husk is blown further than the heavy grain, so the difference in weight separates them.
Question 4 of 6
Sedimentation followed by decantation is used to begin cleaning:
Salt water
Muddy water
Cooking oil
Dry rice
Explanation: The mud settles (sedimentation) and the clear water is poured off (decantation).
Question 5 of 6
Why is filtration alone NOT enough to make muddy river water safe to drink?
It removes only larger dirt, not dissolved impurities or germs
It adds salt
It boils the water
It removes the water
Explanation: Filtration removes visible dirt but not dissolved impurities or tiny germs, so further treatment (like boiling) is needed.
Question 6 of 6
A salt solution is evaporated to dryness. What is left in the dish?
Pure water
The salt
Nothing
Sand
Explanation: The water escapes as vapour, leaving the salt behind in the dish.