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Sink or float? HTML5


Archimede's principle: an object immersed in fluid is buoyed up by a force equal to the weight of the fluid displaced by the object.
You can choose between water or alcohol for the testing liquid. Materials that are less dense than the testing liquid will float.
The density of (fresh) water is 1.0 grams per cubic centimeter (g/cm3) and alcohol is about 0.8 g/cm3.
If you consider the following densities:

  • ice is 0.9 g/cm3
  • walnut is 0.5 g/cm3
  • stone is 2 g/cm3

then you will be able to explain why the ice cube floats in water and sink in alcohol.

Safety precaution: alcohol is a flammable liquid; keep away from all flames.

Click on an object to select it and immerse it in water or in alcohol.

Learning goals

  • To classify objects according to whether they sink or float.
  • To introduce the notion of density (middle school)
  • To teach that a floating body displaces a volume of fluid equal in mass to the mass of the body