Saturday 7 June 2014

Science: The Buoyancy Test!

This is a very simple experiment but it teaches important principles of science.  The important thing is to have fun, do this activity as if you are playing a game! 

I loved how once I set this experiment up my 9 year old without any prompt began to lead the lesson for her 4 year old sister.  They loved it.  They laughed.  They learnt.  This is one of the many things I love about our life home educating.
Anyway, if you want to know how we did the experiment... 
You will need:

  • A large bowl - a washing up bowl will do. 
    We used our fish tank (don't worry we don't own any fish) because it was a large clear container so Harmonie, my four year old, was able to see everything that was happening.
  • Water
  • Lots of small things around the house with different densities.  If you are not sure you could use things like:
    A metal spoon
    A plastic spoon
    A small plate
    A toy figurine (dinosaurs are cool)
    A small stone
    A shell
    A cork
    A feather
    A coin
    An elastic band
    A LEGO brick
    A iron nail
    A lolly stick
    A pen
    A pencil

  • Paper
  • Pen


Fill your bowl with water with a couple of inches room at the top.


Write on one sheet of paper: FLOAT and another: SINK. 

It can be something similar instead.  At the moment Harmonie is starting to read and I am teaching her about the words YES and NO - because she likes them - so I wrote DOES IT FLOAT? on both papers as well and then under one I wrote YES and the other NO.  Like this...




Ask your child to guess whether each item you have collected will sink or float.  Ask them to put it on the paper that says SINK or the paper that says FLOAT.  Let them know that they are hypothesising what will happen. 

Try to fit in these big scientific words where you can as it will help young people to feel familiar with them and give them more confidence in science.
When they have done all there hypothesising, ask them to check whether they are right or not by putting one item in the water at a time.
If your child gets upset that they are wrong (Harmonie did at one point) remind them, as my 9 year old Naomi reminded my Harmonie, that it doesn't matter.  It's about seeing what really happens! 


The best thing about science is hypothesising and not having to be right but learning what is true by doing it for yourself!

The science behind this experiment...

So why do some objects sink and others float?  It's all about density: when the object is heavier than the density of liquid it sinks and if object is lighter than the density of liquid it floats. 

If you want to follow on from this experiment this is a good one to start with: What is Density?


When doing this with older children they might want to write down what they hypothesise in a science notebook
Older children might like to write down the results of what they discovered and then follow on with some of these experiments from my page: Archimedes' principle, Buoyancy and Density

Words to use when doing this activity:

  • Density
  • Buoyancy
  • Sink
  • Float

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