Hi
We're working on our intermolecular forces presentation but have some questions as follows:
Why does boiling point decrease going down Group 0?
When talking about dipoles, do we have to explain why they exist with reference to core charge?
Do we have to cover hydrogen bonding or the covalent character of ionic bond?
How do you pronounce van der waals and delta.
Apart from that, we're fine!
See you on Monday.
jo
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3 comments:
Hi Jo. It's great to see you making such great use of the blog! In answer to your questions...
1. Whenever you're asked to explain why melting or boiling points increase/decrease, it's to do with the strength of the forces between the atoms, ions or molecules. Stronger forces = HIGHER BOILING POINTS. So, you need to think about what happens to the intermolecular forces between atoms of He, Ne, Ar, etc that explains why the boiling points decrease.
2. It would be good to explain why dipoles exist and to give examples of polar molecules (such as CH3Cl) and non-polar molecules (such as CCl4). You'll need to define ELECTRONEGATIVITY and use that to explain why dipoles exist in the first place.
3. Please do cover hydrogen bonding as one of the 3 main types of intermolecular forces. (Really, it's just a specific type of permanent dipole-permanent dipole interaction. HYDROGEN IS NOT A TYPE OF BONDING.) You'll need to give a definition of what it is, plus examples of molecules between which it exists and how the strength of hydrogen bonds compare with permanent dipole-permanent dipole interactions and Van der Waals forces.
4. Van der Waals is pronounced as it appears, except for 'Waals' being pronounced as 'Vaals'. Delta is pronounced exactly the same as it looks - it's just the Greek letter delta.
Hope this helps! I'm looking forward to hearing your presentation (and feeling just a little bit guilty about giving you such a big part of the topic - although it sounds as if you're doing brilliantly so far!).
Mrs Sudbery.
I've just found this website on the internet, which has an audio file and the script to go with it, with teachers talking about intermolecular forces. I haven't listened to it yet, but you may find it useful. The website address is:
http://www.chemistry-react.org/go/default/Tutorial/Tutorial_5040.html
Thank you i'll pass this on to vicky as well
Thank you
jo
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