A LEVEL CHEMISTRY molecular forces

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Melodyharmony
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#1
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#1
Hey guys,

I've come across this question in the past years:
Name:  CamScanner 04-23-2020 11.07.57_1.jpg
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The answers says:
The intermolecular forces between the plasticiser and the polymer molecules are weaker than those between polymer molecules.

Shouldn't it be the other way around? Which is: The intermolecular forces between the plasticiser and the polymer molecules are "stronger" than those between polymer molecules.
And that's why it disrupts the polymer structure, and the polymer molecules move over one another easily?

Would appreciate it if anyone can explain it to me
Last edited by Melodyharmony; 1 year ago
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HarisMalik98
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#2
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#2
No, it is correct.

The idea of a plasticiser is to weaken the intermolecular bonds between polymer chains. If they formed stronger bonds, then that would have the opposite effect.

Typically, the polymers will form strong intermolecular bonds that make the structure rigid. Plasticisers fit inbetween the polymer chains, forming weaker intermolecular bonds than the polymer-polymer interactions. Also, this makes the polymer chains become more seperated, weakening the intermolecular bonds between neighbouring chains. The weak plasticiser-polymer interactions combined with the weakening of the polymer-polymer interactions causes the structure to become more flexible.
Last edited by HarisMalik98; 1 year ago
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ALikesGeetars
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Firstly, a plasticiser is something added to a polymer to make it more flexible. They are mainly used in Plastics to make them more mouldable at a lower temperature

For example, let's say we have a container made of PVC
Name:  PVC Chain.png
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As we can see, the red lines represent the polymer chains. There are strong intermolecular forces in between each chain which makes the plastic strong.

Now if we add a plasticiser:
Name:  PVC Chain with Plasticizer.png
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Size:  14.7 KB
The yellow dots represent the plasticiser molecules, as we can see, the PVC chains are now further apart resulting in weaker intermolecular forces and therefore a more flexible plastic. The polymer molecules can easily slide over eachother and the polymer structure is disrupted by the addition of a plasticiser. Without a plasticiser, the plastic would have to be heated in order to mould it into a shape, and with PVC, if we heat it too much or burn it, it can release Chlorine gas as well as other chemicals called Dioxins which we don't want!

I hope that helped and my 30 second drawings in paint helped lol
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Melodyharmony
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#4
Report Thread starter 1 year ago
#4
(Original post by HarisMalik98)
No, it is correct.

The idea of a plasticiser is to weaken the intermolecular bonds between polymer chains. If they formed stronger bonds, then that would have the opposite effect.

Typically, the polymers will form strong intermolecular bonds that make the structure rigid. Plasticisers fit inbetween the polymer chains, forming weaker intermolecular bonds than the polymer-polymer interactions. Also, this makes the polymer chains become more seperated, weakening the intermolecular bonds between neighbouring chains. The weak plasticiser-polymer interactions combined with the weakening of the polymer-polymer interactions causes the structure to become more flexible.
Oh I get it now! Thank you so much
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Melodyharmony
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#5
Report Thread starter 1 year ago
#5
(Original post by ALikesGeetars)
Firstly, a plasticiser is something added to a polymer to make it more flexible. They are mainly used in Plastics to make them more mouldable at a lower temperature

For example, let's say we have a container made of PVC
Name:  PVC Chain.png
Views: 74
Size:  12.8 KB
As we can see, the red lines represent the polymer chains. There are strong intermolecular forces in between each chain which makes the plastic strong.

Now if we add a plasticiser:
Name:  PVC Chain with Plasticizer.png
Views: 70
Size:  14.7 KB
The yellow dots represent the plasticiser molecules, as we can see, the PVC chains are now further apart resulting in weaker intermolecular forces and therefore a more flexible plastic. The polymer molecules can easily slide over eachother and the polymer structure is disrupted by the addition of a plasticiser. Without a plasticiser, the plastic would have to be heated in order to mould it into a shape, and with PVC, if we heat it too much or burn it, it can release Chlorine gas as well as other chemicals called Dioxins which we don't want!

I hope that helped and my 30 second drawings in paint helped lol
Wow thank you so much. Your drawings make it so much easier to understand
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