17 February 2009

Investigating some different solid materials – and finding out about suspensions and solutions along the way…..

We started out with six different ‘white-coloured’ solids and six different ‘brown-coloured’ solids.  We wanted to find out, by observing carefully,  what might happen if they were stirred into water.

Our ‘white-coloured’ solids were

  • sugar
  • salt
  • washing powder
  • cornflour
  • white powder paint
  • chalk


Our ‘brown-coloured’ solids were

  • instant coffee
  • ground coffee
  • sand
  • brown sugar
  • brown powder paint
  • sawdust


We wanted to measure (by observing) what happened when each material was stirred into water.

We would need to keep everything else the same

  • the same amount of the material
  • the same amount of water
  • the same number of stirs

This is what we did (the method)

  • pour water into a beaker up to the line
  • add one spoon of the material
  • stir twenty times
  • look to see what happens

These are some of our observations of the ‘brown-coloured’ materials

  • the sand sank to the bottom


  • the brown sugar grains and the instant coffee granules ‘disappeared’


(they turned the water brown)


  • most of the sawdust floated


  • some of the ground coffee floated and some of it sank


  • the brown powder-paint turned the water brown (and a bit of it floated)


We recorded our observations in a table


These are some of our observations of the ‘white-coloured’ materials

  • the washing powder bubbled and turned the water ‘milky’
  • the white-powder paint and the cornflour turned the water ‘milky’
  • some of the chalk sank and some of it turned the water ‘milky’


  • the salt and the sugar grains ‘disappeared’ (the water was clear)


We recorded these observations in a table


A few days later, however, some things had changed.

The sawdust had mostly sunk (we wondered why this was; but when we remembered that one of the properties of wood is that it absorbs water, we thought that maybe the sawdust had ‘sucked up’ enough water to make it ‘heavy’ enough to sink)

Everything else, except the salt, the white and brown sugar and the instant coffee, had sunk to the bottom of the beaker; the water had gone back to being clear.  The materials were no longer ‘in suspension’.  This means they are ‘insoluble’ materials; they do not dissolve in water.

There was still no sign of the salt, the white and brown sugar and the instant coffee.  They were ‘in solution’.  They are ‘soluble’ materials; they dissolve in water.

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