Chemistry help ?!?! Watch

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#1
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i don't understand how to put what i know on paper for any chemistry question that comes up on bonding, what do i do?

for example, the other day i did this question:
compare the similarities and differences in the properties and structure of metals and graphite
this is what i wrote: both metals and graphite are giant structures. metals are arranged in regular patterns (in layers) whereas graphite is arranged in hexagonal covalent bonds with weak bonds within their layers; metals are malleable because their layers can slide whereas graphite's layers make it slippery. Both metals and graphite have high melting and boiling point due to strong inter molecular forces between the molecules. They both conduct electricity; graphite has delocalised electrons that carry charge whereas metals have a 'sea' of electrons that can carry the charge.

1)i only got 3 marks and this was out of 6
2) i checked the markscheme and where i said "have high melting and boiling point due to strong inter molecular forces between the molecules" it said they had high melting/boiling points due to strong bonds holding them but i'm confused bc i though melting/boiling point is dependent on intermolecular forces
3) how do i get full marks? did i miss something or say something inccorect/vague?
4) any tips on how to revise bonding in a way i can apply it?
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??
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Ray_Shadows
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is this a-level or gcse
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Anonymous1502
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Memorise the mark scheme answers.You learn what the examiner wants through doing the past papers!
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(Original post by Ray_Shadows)
is this a-level or gcse
GCSE
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BF19
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During melting and boiling, it is the 'bonds' that are braking, which require a lot of energy to break. The intermolecular forces between layers aren't actually that strong and that is why the use graphite in pencils, as the layers can easily slide.
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(Original post by Anonymous1502)
Memorise the mark scheme answers.You learn what the examiner wants through doing the past papers!
I have done quite a few questions of bonding but if they throw a new one in to the actual paper, i want to be able to answer that so i wanna know how i can apply the knowledge to the questions rather than just memorise them but my fallback plan is just to memorise them all.
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Ray_Shadows
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(Original post by :)Esss:))
GCSE
graphite has a strong melting point because of it's strong covalent bonds between the molecules

also i would add about the solubility, for graphite its insoluble because it's sheets are hard to break , metals are also insoluble because of the storng metallic bonds

just keep practicing it
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(Original post by Ray_Shadows)
graphite has a strong melting point because of it's strong covalent bonds between the molecules

also i would add about the solubility, for graphite its insoluble because it's sheets are hard to break , metals are also insoluble because of the storng metallic bonds

just keep practicing it
so why do simple covalent structures have low melting/boiling points then? don't they have strong covalent bonds as well? sorry i'm just a bit confused on this
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Ray_Shadows
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(Original post by :)Esss:))
so why do simple covalent structures have low melting/boiling points then? don't they have strong covalent bonds as well? sorry i'm just a bit confused on this
well they are simple molecules so weak bonds i'm guessing
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(Original post by Ray_Shadows)
well they are simple molecules so weak bonds i'm guessing
aah ok i checked my textbook again and this is what it says:
"in simple covalent structure the forces of attraction between individual molecules is relatively small- they have weak intermolecular forces. intermolecular forces increase with the size of the molecules so larger molecules have higher melting and boiling points" but in the same book it also says "there are weak intermolecular forces between the layers in graphite" so does that mean that the forces between the layers don't matter when considering melting/boiling points??
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Ray_Shadows
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(Original post by :)Esss:))
aah ok i checked my textbook again and this is what it says:
"in simple covalent structure the forces of attraction between individual molecules is relatively small- they have weak intermolecular forces. intermolecular forces increase with the size of the molecules so larger molecules have higher melting and boiling points" but in the same book it also says "there are weak intermolecular forces between the layers in graphite" so does that mean that the forces between the layers don't matter when considering melting/boiling points??
yeh i guess so

you learn about the effects intermolecular bonding and its effects if you do a-level chemistry hence why i'm little confused
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(Original post by BF19)
During melting and boiling, it is the 'bonds' that are braking, which require a lot of energy to break. The intermolecular forces between layers aren't actually that strong and that is why the use graphite in pencils, as the layers can easily slide.
um ok so do intermolecular bonds break or covalent bonds?
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(Original post by Ray_Shadows)
yeh i guess so

you learn about the effects intermolecular bonding and its effects if you do a-level chemistry hence why i'm little confused
i don't know if i need to know this, i've just seen this type of question come up quite a lot. i should check the specification i guess
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Ray_Shadows
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(Original post by :)Esss:))
i don't know if i need to know this, i've just seen this type of question come up quite a lot. i should check the specification i guess
yeh do that
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BF19
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(Original post by :)Esss:))
um ok so do intermolecular bonds break or covalent bonds?
Its the strong covalent bonds that need to be broken and this needs a high amount of energy. The intermolecular forces still need to be overcome, but this doesn't need much energy at all. The high temperatures are needed to break the actual bond.

If feel like if you do a level chemistry, a lot of this will clear up.
But just remember for macromolecular structures the covalent bonds need to be broken.

However in simple molecular structures, the intermolecular forces need to be broken- not the bonds. This is because the subunits of simple covalent structures exist as molecules, unlike atoms for macromolecular structures, therefore the intermolecular forces are only needed to melt it.
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#17
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(Original post by BF19)
Its the strong covalent bonds that need to be broken and this needs a high amount of energy. The intermolecular forces still need to be overcome, but this doesn't need much energy at all. The high temperatures are needed to break the actual bond.

If feel like if you do a level chemistry, a lot of this will clear up.
But just remember for macromolecular structures the covalent bonds need to be broken.

However in simple molecular structures, the intermolecular forces need to be broken- not the bonds. This is because the subunits of simple covalent structures exist as molecules, unlike atoms for macromolecular structures, therefore the intermolecular forces are only needed to melt it.
yh im hoping to do a level chem and thank you, i think that really cleared things up in my head
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BF19
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(Original post by :)Esss:))
yh im hoping to do a level chem and thank you, i think that really cleared things up in my head
Good, glad to hear
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