OCR Salters Chemistry B F332 Advance Notice May 2011 Polymers on the move

Original post by bertiejess

Hi everyone, just wondering whether anyone would be able to answer a question for me - Why did the oil price shock of the 1970s lead to an increase in the use of plastics in transport? Thank you :smile:

By using polymers over traditional materials such as steel they could reduce the weight of vehicles and therefore increase fuel efficiency (which was necessary due to the skyrocketing of motor oil prices). However, this isn't a perfect solution as most polymers themselves are made from organic compounds that come from crude oil.

Reply 62

Anybody got any predictions for what the 6 mark question on the advance notice is going to be about?

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Hanz_a93

OP

15

Original post by Hudzy

Anybody got any predictions for what the 6 mark question on the advance notice is going to be about?

Im guessing hydrogen bonding and why some polymers are soluble in water and why some are not. (They may ask you to draw a diagram to illustrate the bonding aswell)

The other might be to explain initiation, propagation, termination using equations to show how chlorine radicals catalyse the breakdown of methane or ozone

Reply 64

bertiejess

Original post by Hudzy

By using polymers over traditional materials such as steel they could reduce the weight of vehicles and therefore increase fuel efficiency (which was necessary due to the skyrocketing of motor oil prices). However, this isn't a perfect solution as most polymers themselves are made from organic compounds that come from crude oil.

Thank you

Also, why were vechicle paints traditionally based on several layers of different high molecular mass polymers?

Reply 65

TLittler

Original post by Hudzy

Started my chemistry revision by making some notes for the advance notice article today, included information suggested by my teacher and incorporated some of the suggestions on here. Hopefully it can be of some use to others.

If you find any errors or have any suggestions of other relevant points let me know. :smile:

this is good but im sure youve got some of the butadiene bit wrong, youve drawn it with 5 carbons for a start, unless im getting really confused!

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Polymers on the move.pdf200.7KB

Original post by TLittler

this is good but im sure youve got some of the butadiene bit wrong, youve drawn it with 5 carbons for a start, unless im getting really confused!

Yeah I took it off the internet without realising it had an extra carbon. I posted an updated version but you probably missed it. I'll change the version on the old post to stop confusing people :tongue:

Here is the update anyway.

Reply 67

TLittler

yeah sorry man, i realise this has been brought up like 4 times, also could you clear up the double bond thing on the butadiene, i though both bonds opened up, or is this not the case?

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Original post by TLittler

yeah sorry man, i realise this has been brought up like 4 times, also could you clear up the double bond thing on the butadiene, i though both bonds opened up, or is this not the case?

They do, but just like in standard additional polymers (e.g poly(ethene)) one bonding electron goes in each direction (not sure if that's well worded, but if you draw/imagine poly(ethene) it should make sense). The two electrons between the 1st and 2nd carbon form a single bond and so do the electrons between the 3rd and 4th. There is also an electron from the 2nd carbon and one from the 3rd carbon that join to form a single bond, but as there was previously a single bond between the 2nd and 3rd carbon this is now a double bond.

Reply 69

croag

12

I am so worried for this, I don't know anything about polymers at all. I'm predicted an A and I got an A in the Jan modules, but there is no chance on Friday. I don't know any of this topic.

I'm assuming they'll ask us about that properties table, which is OK, but I have no idea why some polymers are soluble in water and some aren't.

Reply 70

Rei5

yeah could someone plz explain solubility plz???? seems like this will definately come up!

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Original post by croag

I am so worried for this, I don't know anything about polymers at all. I'm predicted an A and I got an A in the Jan modules, but there is no chance on Friday. I don't know any of this topic.

I'm assuming they'll ask us about that properties table, which is OK, but I have no idea why some polymers are soluble in water and some aren't.

Original post by Rei5

yeah could someone plz explain solubility plz???? seems like this will definately come up!

I'm not sure if the solubility of polymers will come up as there was a 7 mark question on it on the January paper, but i'll explain it anyway. For something to be soluble it has to be able to form bonds at least as strong as permanent dipole-dipole dipole (although these will only be slightly soluble). For something to dissolve in water it needs to disrupt the hydrogen bonds and bond with the water molecules itself.

The example always used is poly(ethenol) which contains an OH group to allow hydrogen bonding. The hydrogen in the O-H has a partially positive charge and is attracted to the lone pair on the partially negative charge in another polymer chain. They can also hydrogen bond with water molecules in the same way.

The number of OH groups is very significant. Too few and not enough hydrogen bonds can form between the polymer and water molecules and it will be virtually insoluble. However, too many and the intermolecular forces between polymer chains will be too strong to be disrupted by the water molecules and will not dissolve. Therefore an intermediate number of OH groups are needed.

Reply 72

joestevens2092

3

Original post by Rei5

yeah could someone plz explain solubility plz???? seems like this will definately come up!

solvent solute intermolecular bonds must be strong enough to overcome the intermolecular bonds within the solute

Reply 73

bertiejess

Is this correct for the reaction between ethanol and propanoic acid?
CH3-CH2-COH=O + CH2OH-CH3 -----> CH3-CH2-C=O-O-CH2-CH3 + water

Reply 74

Rei5

Original post by Hudzy

I'm not sure if the solubility of polymers will come up as there was a 7 mark question on it on the January paper, but i'll explain it anyway. For something to be soluble it has to be able to form bonds at least as strong as permanent dipole-dipole dipole (although these will only be slightly soluble). For something to dissolve in water it needs to disrupt the hydrogen bonds and bond with the water molecules itself.

thanks mate! so can a permanent dipole-permanent dipole force overcome hydrogen bonding in water to become solubl??

The example always used is poly(ethenol) which contains an OH group to allow hydrogen bonding. The hydrogen in the O-H has a partially positive charge and is attracted to the lone pair on the partially negative charge in another polymer chain. They can also hydrogen bond with water molecules in the same way.

The number of OH groups is very significant. Too few and not enough hydrogen bonds can form between the polymer and water molecules and it will be virtually insoluble. However, too many and the intermolecular forces between polymer chains will be too strong to be disrupted by the water molecules and will not dissolve. Therefore an intermediate number of OH groups are needed.

thanks! so basically anything with an -OH attached will be soluble to a degree?

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Original post by Rei5

thanks! so basically anything with an -OH attached will be soluble to a degree?

Yes

Reply 76

username511256

Just wondering if we need to know the uses and properties of specific polymers?

Reply 77

UKlaw94

I find the whole "box 1" so confusing :/

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