Science Club – Buoyancy


With a couple of friends, I’ve started to run a weekly Science Club for home educated children. Our children range from one to eleven, so I try to put together activities that are interesting and challenging for all ages.

We’ve been running for ten weeks now, and I’ve finally got around to putting together a post about it. I thought it might be worth making available the plans that I’ve made and some of the visual aids I’ve been using, in case someone else could make some use of them.

I’m having a lot of fun running the group and preparing the sessions, and I think that I’m getting better at it!

Our first week was all about floating and sinking.

Here’s the plan I was working from:


Floatation Experiment: what will float?

First we make predictions: look at the sheet, tick the items that you think will float.

I made a sheet with drawings of the objects we were testing, so that pre-readers could also join in (you can see the sheets here: BuoyancySheets).

Then we test our predictions, and record our results: put each item in the water, see if they float, circle the items that float, on your sheet.

Finally we make our conclusion: did any items surprise us? What do all the floating items have in common?

Things float because they weigh less than the water that they displace. We can work out in advance whether or not something will float by calculating its density. A ball of plasticine will sink. But a plasticine boat will float.

Individual Task:

Each child can make their own boat out of plasticine.

Bigger children can draw their boat and predict how many pennies it will hold before it sinks.

Biggest children can calculate the density of their boat, then predict how many pennies it will hold before it sinks.

Gather Together for the Conclusion:

We can test all the boats and see how many pennies they hold before they sink.

We’ve looked at solid objects, so far, but what happens when you pour a liquid on top of water? Some liquids sink and some liquids float.

Density tower demonstration.

This was the most unsuccessful part of the session. The children got bored as I slowly added washing-up liquid to water and milk to that. They weren’t as impressed by the visual effect as I had hoped. In later weeks I’ve cut down on demonstrations!

Paper clips sink, but they can ‘sit’ on top of the water using surface tension. Some small animals can exploit surface tension to run across water, like pond skaters. If you like, you can try and make a pond skater after snack time.

Break for drink and snack

Optional Extensions:

  • Boats colouring sheets – no supervision required.
  • Making 3-d shapes from nets – smaller children will need help.
  • Sorting 3-d shapes – supervision needed to ensure nothing gets lost.
  • Make a captain’s hat – smaller children will need help.

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