Nothing to buy. Ten minutes with two balloons, a stick and some string. This is not homework and it will not be marked. It settles one question that almost every child gets wrong and that everything in Science 5 after this week depends on.
The activity: weighing air
minutes: 10Materials: two balloons or two small plastic bags, a stick or a ruler, string, and a chair or door handle to hang it from.
Tie a string to the middle of the stick and hang it up so it balances.
Tie one empty balloon to each end. Move them until the stick is level.
Ask: <q>If I blow up one balloon, what will happen?</q> Wait for an answer before doing anything.
Ask the one that matters: <q>Why do you think that?</q>
Now take one balloon off, blow it up, tie it, and hang it back in the same place.
Watch. The blown-up side goes <b>down</b>.
Ask: <q>What does that tell us about air?</q> The answer you are listening for is that air weighs something.
Three things to avoid
What usually happens
Instead
Telling your child that air has weight before you do it.
The whole value is in the prediction being wrong. If you say it first, they will agree with you and nothing will have changed.
Saying <q>air is nothing</q> or <q>the balloon is empty</q> in ordinary conversation.
An empty balloon and a blown-up one are the same balloon with different amounts of matter in them. This one phrase, used casually, undoes the whole week.
Letting <q>it's just air</q> settle an argument.
Ask <q>just air made of what?</q> Air is a mixture of real substances with real mass, and your child is being taught to treat it that way.
Three signs it is working
They say <q>it takes the shape of the container</q> without being prompted.
They correct somebody who calls sand a liquid.
They ask where the water went when something dried, instead of saying it disappeared.
If you only have time for one part, make it step 4 — <b>why do you think that?</b> A prediction with a reason is science; a prediction without one is a guess, and this week is where the difference starts to be assessed.