IMO Practice Test — Matter & Its Changes

Salt water left in a shallow dish in the Sun leaves salt behind because only the ___ evaporates.

Water is unusual because we easily see it as all three states:

Mixing flour, water and baking it into a cake is irreversible because a ___ substance is formed.

A mixture of sand and water can be separated by ___ because sand does not dissolve.

Different solids melt at different temperatures; butter melts easily but iron needs very great…

Melting and freezing can be reversed. Frozen water can melt and then be frozen again, so they are ___ changes.