12 replies to this topic

[Pammy]

This is not actually a serious question at all, but just something that annoys me

why are water and ammonia Polar ??
Because you can actually draw a line of symmetry on them

I asked my chemistry teacher and she said she actually wasn't sure, but she thought it was because they are not straight chains.

Does anyone agree with me ????

[AM4R]

yup i do!

Its stupid actually! Chem is wierd like!

Back to what you asked i dont know, lol!

[ad absurdum]

Well the molecules are polar due to uneven distribution of electrons as the molecules is not symmetrical and this creates a dipole. For example if you look at carbon dioxide, there is a large enough electronegativty difference between carbon and oxygen to suggest that the molecule will be polar. However, the molecule is arranged with a carbon atom in the middle and two oxygen atoms joined at either side and overall the molecule is not slightly negative or slightly positive in places so the molecule is not polar.

However, if you look at a water molecule, it is "bent". The molecule is not arranged in a straight line so the part where the hydrogen atoms are bent towards will actually be slightly positive, whilst the "bare" end of the oxygen atom will be slightly negative. So overall there is a slight dipole on the molecule thus it is polar. Same idea with ammonia.

It's hard to explain without pictures, but if you go to www.wikipedia.org and search for the chemicals you will be able to see their structures better and hopefully see where I'm coming from a bit better.

I'm surprised that your chemistry teacher does not know this

[AM4R]

true lol

[Nathan]

I'm surprised that your chemistry teacher does not know this

my teacher knows it, but it's only his first year teaching higher so he keeps telling us Uni-related stuff that we really don't need to know...he has got better as the year went on tho

[ad absurdum]

my teacher knows it, but it's only his first year teaching higher so he keeps telling us Uni-related stuff that we really don't need to know...he has got better as the year went on tho

Haha, that must have got annoying But at least he's getting better.

Our teacher is quite the opposite, he's been teaching for decades, and he is a great teacher apart from every couple of minutes he will go off at a tangent to a completely unrelated story (which always turns into the exam board, golf, R.P. Feynman or sex). We have another chemistry teacher (male) who is an alcoholic and never taught us a thing and another (female) who is good but very attractive so we spend most of our time trying to invite her to parties rather than learning chemistry.

[AM4R]

lol, how old is she?

[Nathan]

we have a fit chem teacher as well...i think she's like 25....but she's leaving to go to some lucky school in edinburgh

[Pammy]

well.....I am a girl.....and my teacher is female......and i don't bat for the other side......sooo.....I can't really contribute to this convo

[Nathan]

to get back onto topic here, (kinda)

polar substances disolve in polar substances

non-polar substances dissolve in non-polar substances

hence why you can't get oil and water to mix...however, add an OH on the end of it, it becomes polar and it'll dissolve in water

and also, a joke for you all;

why did the white bear dissolve in water??


because it was a polar bear

yes, lame, i know, but i bet it'll make you remember that water is polar in the exam

[eyecandy]

^ lmao.. wat highers reduce us too

[ad absurdum]

lol, how old is she?

She's 24 or something like that

we have a fit chem teacher as well...i think she's like 25....but she's leaving to go to some lucky school in edinburgh sad.gif

Yeah, that's the same with all of our attractive teachers this year

why did the white bear dissolve in water??

because it was a polar bear tongue.gif

[dfx]

You may ask, however, why for example CCl4 is not polar and that is due to the 3D shape of the molecule such that all dipoles cancel out. The shape of the molecule is determined by electron repulsion theory Lone Pair-Lone Pair repulsion > Lone Pair-Bonding Pair repulsion > Bonding pair-Bonding pair repulsion. But that's not in the Higher lol.