Look at this clear jar. Salt was stirred into the water until you could not see a single grain. Has the salt gone for good, or is it still in there somehow?
Hands up: gone forever, still there, or not sure?
Here is a second jar. You can still see the sand grains in the water. That is a mixture: the materials are together but keep their own properties.
Our first jar looks clear. When salt disappears into water but is still there, that is a solution.
Dissolved does not mean gone. If the salt is still in the clear water, how could we get materials back out?
Two puzzles for your group. First: when salt dissolves and the water looks clear, where has the salt gone? Second: if we pour sandy water through filter paper, what will be caught and what will run through?
Agree one prediction for each puzzle and be ready to say why.
Watch the set-up carefully. First we will try filtering: pouring sandy water through paper with tiny holes so undissolved bits are caught. Then we will pour a little clear salt solution into shallow dishes for the windowsill. That starts evaporation, when water slowly dries away and can leave dissolved solid behind.
Before anything is poured: what do you think will be left in the filter paper, and what will look different in the dishes after a few days?
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