Nothing to buy. Two minutes to set up, one minute a day for a week, and a five-minute conversation at the end. It settles the single idea most Grade 6 learners get wrong, and it settles it with evidence rather than with an explanation.
The activity: salt that comes back
minutes: 10 across a weekMaterials: a saucer or the lid of a jar, half a glass of water, and a spoonful of salt.
Stir the salt into the water until it disappears completely. Let your child do the stirring.
Ask: <q>Where has the salt gone?</q> Whatever they say, do not correct it.
Ask: <q>Do you think we could get it back?</q> Then: <q>Why do you think that?</q>
Pour a little of the salty water into the saucer. Put it on a sunny windowsill.
Each day, look at it for a few seconds together. Say nothing more than <q>anything different?</q>
When the water is gone, look at the white crust in the saucer. Ask: <q>What is that?</q>
Let them taste a grain of it. It is salt. Ask: <q>So was the salt ever really gone?</q>
Three things to avoid
What usually happens
Instead
Saying <q>the salt dissolved, it's still there</q> at step 2.
That is the answer, and giving it at step 2 removes every reason to look at the saucer for the rest of the week. The waiting is the whole activity.
Saying <q>it disappeared</q> or <q>it's gone</q> in ordinary kitchen conversation.
Your child is being taught that matter is not destroyed. Sugar in coffee, salt in soup — the word to reach for is <em>dissolved</em>, and it costs nothing to use it.
Treating a wrong prediction as a mistake.
A child who predicted the salt was gone forever and then saw it come back has learned more than one who guessed right. Say <q>good — now we know</q> and mean it.
Three signs it is working
They ask <q>is it still the same thing?</q> about something in the kitchen.
They say <q>you can't get that back</q> about a burnt or cooked food, and can say why.
They correct somebody who says the sugar disappeared.
If you only have time for one part of this, make it the last question: <b>so was the salt ever really gone?</b> Everything the class does with burning, rusting and cooking for the rest of the year rests on the answer being no.