IMO Practice Test — Matter & Mixtures
6 Questions • 12 min • Olympiad level
12:00
Question 1 of 6
hard
Rainwater is fairly pure because, in the water cycle, it formed from water that had…
Evaporated, leaving impurities behind
Frozen solid
Been filtered by sand
Boiled in a pot
Explanation: Evaporation lifts pure water vapour, leaving salts behind.
Question 2 of 6
hard
Why does a balloon shrink a little when put in a cold fridge?
Cold gas particles move closer together
The balloon eats air
Air turns solid
It loses colour
Explanation: Cooling makes gas particles draw closer, so the balloon shrinks.
Question 3 of 6
hard
To separate a mixture of salt, sand and iron filings, a good first step is to use a…
Fire to burn salt
Magnet to remove iron
Fan to blow salt
Freezer
Explanation: A magnet removes the iron, then water and filtering separate the rest.
Question 4 of 6
hard
Why is a fruit salad a good example of a mixture you can easily separate?
It cannot be undone
The fruits melt together
It becomes one new fruit
You can still pick out each fruit
Explanation: Each fruit keeps its identity and can be picked out.
Question 5 of 6
hard
A gas can dissolve in a liquid too; the fizz in soda water is dissolved…
Iron
Sand
Carbon dioxide gas
Oil
Explanation: Soda fizz is carbon dioxide gas dissolved in water.
Question 6 of 6
hard
If you keep adding sugar to a glass of water, at some point no more dissolves. The water is then…
Frozen
Empty
Saturated (full)
Boiling
Explanation: When it can hold no more, the solution is saturated.