Learn more physics!
How can something float in one fluid but not in another fluid?
- John Wayde
An object will float in a fluid if its average density is less than
that of the fluid. An ice cube will float in water but will sink in
ethanol; ice is only a tiny bit less dense than water, and the ethanol
is less dense still. Oil too is less dense than water and some things
which float in water will sink in oil.
Dissolving lots of salt in water will make it more dense, allowing
more different kinds of things to float in it which would otherwise
(republished on 07/31/06)
Follow-up on this answer.