Re: Why do things float more easily in salt water than in normal fresh water?

Sorry for the late reply - my modem was down for the past few weeks and I
just got it replaced...

Basically, the molecules of salt solution are joined more tightly together
than those of fresh water, which are loosely-linked.  This means that for 
the same volume of liquid, the salt solution is denser, and therefore, is 
able to hold objects afloat more than fresh water can.

BTW, Density = mass per unit volume

If you were to cut two slices of potato about 1/2" thick each and drop them
into respective salt solution (8-10 large spoonfuls of salt in a big jug) 
and fresh water, the one in salt solution floats because the potato's
density is less than that of the salt solution;  the other sinks in fresh
water because the density of the fresh water is less than that of the 
potato, hence cannot support the weight of the potato.

One more example of density - if you were to drop a solid piece of clay
into water, it would sink.  But if you hollowed it out into say, a boat
shape, it floats.  The reason is that the solid piece is denser than the 
water, so it sinks.  However, in flattening out the shape into a boat, you
have changed the density of the solid blob into one that holds air, which
is less dense than water.  This causes the overall density of the boat to 
be less than that of the water, and so it floats.

Ref:  encyclopedia of Science Projects by The SHOOTING STAR Press

Best regards,
mikeho
mikehopc@mbox2.singnet.com.sg