On Apr 27, 2008, at 3:08 PM, BB wrote:
I'm a pet grooming educator and I need help in explaining to groomers how an
alcohol-based ear cleaner will displace water that might get into an
animal's ear during bathing. Can you help me explain?
I love the pepper and soap experiment for surface tension. I think I shall
borrow it for my upcoming online class on shampoos. Previously I have used
an experiment that requires a paper "boat". If you place a paper boat (made
from an index card in the shape of an arrow) in a pan of water and put a
drop of dish soap behind the boat, it will propel the boat across the water.
Same principal. The pepper is much easier, thanks!
It's funny you should ask me about ear drying, because I am just recovering from an ear infection and complications related to it. Keeping your ears dry can help prevent ear infections. Alcohol is used--in drops--to keep ears dry--but as I tell my students, all you need is the large cheapo container of rubbing alcohol (isopropanol) that you find in a pharmacy, not the expensive little vial with the exact same stuff in it with the glossy label on it saying it is to be used specifically to prevent ear infections.
The reason I took so long to get back to you (and others are still waiting for me, in line, to write them, too!) is because this bacterial infection moved from my sinuses to my ear and then my eyes and THEN I went to the emergency room for bacterial meningitis which almost killed me last weekend. No kidding! I'm recovering and shaken and so grateful for antibiotics.
So now I'm still fairly listless, but I just barely have the energy to answer your question.
Alcohol makes a good drying agent.
Alcohol forms a strong sort of attraction to water through a special electrostatic attraction called a "hydrogen bond". I have never liked the name of this sort of attraction because it is not as strong as a real bond, and unlike real bonds, it breaks a lot more easily.
In fact, water hydrogen "bonds" to itself, too, but these attractions between water molecules are obviously easy to break--just stick your finger in a glass of water and you are separating water molecule from water molecule, by breaking these so-called hydrogen bonds. (If they were as strong as a real bond, the water would be solid.)
Anyway, alcohol forms this attraction to water, yet alcohol can evaporate---become a gas---fairly easily.
I imagine the two molecules holding hands, so to speak, and flying off around the room together. Like molecular lovers. How romantic! So, in short, alcohol attracts water, and then flies around the room as a gas with a bit of the water clinging to it. In traveling along with its newfound attractor, the water leaves its previously wet area.
Now I'm pooped and have to go back to bed so that I can cough a lot and keep myself awake. I hope that helped!