Intro Biology Question regarding water (chemistry related)? PLEASE HELP!

Question

Which statements about water and 'anti-water' (something that is the opposite of water in terms of molecular properties) should be true?

Select one:
a. Lubricants such as engine oil must work because they don't interact with other surfaces
b. Non-stick surfaces such as teflon aid cooking by holding on to water molecules to keep the food from sticking

 

Can you please help me with this? I am stuck and a bit confused. I am kind of thinking its a but I don't understand the answer options very well. I truly appreciate the help!

Answer 1

Remember, water has strong intermolecular forces as it is a polar molecule and can hydrogen-bond to other water molecules (thus the high surface tension mentioned in the lizard problem). Nonpolar molecules like oils generally do not mix with water because they do not make strong intermolecular interactions with water molecules.  Thus the saying "oil and water don't mix" and the reason you have to shake your Italian salad dressing (because the oil is on the top and the water/vinegar with all of the good spices is on the bottom!).

 

Molecules and substances like oil are sometimes called "anti-water" because of their weak forces and their tendency to not mix with water.  They are also called "hydrophobic" (water-fearing).

 

Statement (a) talks about lubricants working because they don't interact with other surfaces.  Think about that for a minute - if the oil strongly interacted with other surfaces, wouldn't it be "sticky"?  Would that help with lubrication?  For lubrication, you want to let the surfaces slide freely past each other, so this makes sense that oil NOT interacting with other surfaces would cause a slippery situation that is desired. :) 

 

Statement (b) talks about Teflon cookware, and says that it works by holding onto the water molecules.  If it held onto the water molecules in the food, wouldn't it be holding onto the food itself?  That would make it stick, not non-stick!  Also, if you look in your book or on the internet, you can see that the structure of Teflon is very similar to a non-polar hydrocarbon, except with a bunch of F attached instead of H. So this statement does not make sense, as Teflon should fall into the "anti-water" (hydrophobic) classification. ;)

 

Hope that helps!