Monday night I left a glass, maybe third full of ice, and a bit of cola in the bottom. the bit you can’t really get without a straw or choking on ice cubes.
next morning, the cola was at the bottom and the water above it was clear.
so I shook it up till it was mixed and left it again for another night.
it didn’t separate.
my theory is that the ice had air in it which made it float.
am I right?

I think it is simply a density difference, purple. The cola is a sugar solution and so is more dense than water. With no mixing other than diffusion, the water slowly accumulated on the top of the cola solution. When you mixed it, the density gradient disappeared.

would it come back eventually?

purple said:

would it come back eventually?

Do you mean would it form layers again? No.

morrie said:

purple said:

would it come back eventually?

Do you mean would it form layers again? No.

Actually, there is a balance between two opposing phenomena:

1: The lowering of the potential energy that results from the denser sugar moving to the bottom and displacing the water that was there.
2: The increase in entropy that results from the thorough mixing of the components.

In earth’s gravity, the increase in entropy far outways the lowering of the potential and the mixing is more-or-less complete and irreversible. But, in a high-powered centrifuge, one can achieve a definite concentration gradient, and I understand that this effect is used in biochemistry research.

KJW said:

But, in a high-powered centrifuge, one can achieve a definite concentration gradient, and I understand that this effect is used in biochemistry research.

This is with caesium chloride solutions, not sugar solutions. The density difference between sugar and water might not be sufficient even with an ultracentrifuge.