(republished on 07/24/06)
Hi Sally- Schools often try to cut things up into neat categories, but that doesn't make it a good way to think. We try to make our answers make sense but our categories don't really mean much. Nature doesn't divide up neatly that way, and certainly not along the lines of our site's categories. That's why many of our answers show up in more than one category.
The way oil and water don't mix is usually thought of as being a chemical fact, although it follows from the physical properties of their molecules. That oil sits on top also involves gravity, since it's what makes one side 'top' and the other 'bottom'.
This answer, for instance, is going in (at least)
Making Stuff Move
States of Matter and Energy
Boiling, Evaporating & Condensing
Underwater and in the Air
(published on 03/27/07)