Qxi.xli
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In my notes, it says that graphite has a high melting point cuz the covalent bonds need a lot of energy to break. but i thought its the VDW forces that are btwn the layers which would be broken?

could someone clarify? thankss
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TurtlePowerXII
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I’m pretty sure the covalent bonds are stronger than the vdw forces in graphite.
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Qxi.xli
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(Original post by TurtlePowerXII)
I’m pretty sure the covalent bonds are stronger than the vdw forces in graphite.
Yhhh exactly
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Pigster
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(Original post by vix.xvi)
In my notes, it says that graphite has a high melting point cuz the covalent bonds need a lot of energy to break. but i thought its the VDW forces that are btwn the layers which would be broken?

could someone clarify? thankss
Consider a metal, which consist of layers of metal atoms which can slide, hence why a lot of metals are soft and why adding a few larger atoms (to make an alloy) disrupts the layer structure making them harder. Metals have strong metallic bonds which need to be overcome before melting.

Compare to graphite...
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mintchocchip
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Covalent bonds between carbon atoms. VDW are between different molecules.
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TurtlePowerXII
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(Original post by vix.xvi)
Yhhh exactly
So wouldn’t that mean more energy would be needed to break the covalent bonds? Also that the vdw forces would be broken as well once the covalent bonds have been broken?
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DrdBsClassroom
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Yes, you're right that there are vdW between layers, and these are weak and easy to overcome without much energy.
HOWEVER, we're not talking simple molecules here.
In order for graphite to be a liquid, the different bits of the structure must be able to move independently of one another (which for a simple molecule like ammonia can be achieved without needing to break the covalent bonds). In graphite every layer contains thousands of atoms.
So yes, the covalent bonds do need to break, which is why the melting point is so high.
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Qxi.xli
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(Original post by DrdBsClassroom)
Yes, you're right that there are vdW between layers, and these are weak and easy to overcome without much energy.
HOWEVER, we're not talking simple molecules here.
In order for graphite to be a liquid, the different bits of the structure must be able to move independently of one another (which for a simple molecule like ammonia can be achieved without needing to break the covalent bonds). In graphite every layer contains thousands of atoms.
So yes, the covalent bonds do need to break, which is why the melting point is so high.
thank you!!
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