If you mix 1 cup isopropyl alcohol (rubbing alcohol) with 1 cup of water, will your cup measurer read two cups? If not, why not?

rlaj	Probably not, it has something to do with the big molecules making room for smaller molecules. Jan 20 05, 8:32 PM

TheAlphaWolf

Why is it that when you drop a drop of alcohol into some water it acts all strange? Jan 20 05, 9:32 PM

peasypod

It acts *strange* because the alcohol displaces the water. There are spaces between the molecules of liquid water. The alcohol molecules fit between the molecules in the water solution. This causes the final volume of the mixture to be less than the sum of the initial volumes. Jan 20 05, 9:59 PM

TheAlphaWolf

ummm... but doesn't everything displace water? Jan 21 05, 9:58 PM

peasypod

I think you are referring to the physical displacement (ala Archimede's) rather than the molecular displacement. Jan 21 05, 10:13 PM

upspilot

The alcohol does not "displace" the water, it simply interdisperses among the spaces created by the water molecules. In other words, alcohol "fills in the gaps." It's just the same as a bowl full of marbles into which someone pours water. The bowl doesn't get more full but it does get heavier. One has added mass without volume. Aug 22 07, 12:28 AM