IMO Practice Test — Matter & Its Changes
6 Questions • 12 min • Olympiad level
12:00
Question 1 of 6
hard
Salt water left in a shallow dish in the Sun leaves salt behind because only the ___ evaporates.
Air
Salt
Heat
Water
Explanation: Water evaporates and the salt is left behind.
Question 2 of 6
hard
Iron slowly turning into reddish rust in damp air is an example of a change that is…
Irreversible
Reversible
Melting
Freezing
Explanation: Rusting forms a new substance and cannot be undone.
Question 3 of 6
medium
Why can a liquid be poured but a solid cannot?
Liquids are colder
Solids are heavier
Liquid particles can slide past each other
Solids are wet
Explanation: Liquid particles slide and flow; solid ones stay fixed.
Question 4 of 6
hard
Evaporation and condensation together keep happening in nature as part of the…
Light cycle
Food chain
Water cycle
Day cycle
Explanation: These changes drive the water cycle.
Question 5 of 6
hard
Melting and freezing can be reversed. Frozen water can melt and then be frozen again, so they are ___ changes.
Burning
Irreversible
Permanent
Reversible
Explanation: Melting and freezing can go back and forth — reversible.
Question 6 of 6
hard
We can get the salt back from salty water by letting the water…
Freeze the salt away
Evaporate, leaving the salt
Burn
Dissolve more
Explanation: Evaporating the water leaves the salt behind.