The Student Room Group

Bond breaking and intermolecular force A level

When boiling a ionic substance do you BREAK the ionic bond or overcome it? And with Simple covalent compound do you overcome or break the intermolecular forces?
Reply 1
Ionic bonds are overcome because it's not a "physical" bond, it's more of an association due to the electrostatic attraction between the different charges. For simple covalent, you are overcoming the intermolecular forces because that is what keeps the molecules together, and breaking the covalent bonds between atoms would require a lot of energy. Giant covalent structures are the only type where the (covalent) bond is broken as opposed to forces being overcome :smile:
Reply 2
Original post by cyberhex
Ionic bonds are overcome because it's not a "physical" bond, it's more of an association due to the electrostatic attraction between the different charges. For simple covalent, you are overcoming the intermolecular forces because that is what keeps the molecules together, and breaking the covalent bonds between atoms would require a lot of energy. Giant covalent structures are the only type where the (covalent) bond is broken as opposed to forces being overcome :smile:

its really confusing because I was taught to says bonds are overcome. SO can I say in a giant covalent structure the covalent bond is overcome hence the higher melting point/boilingpoint?
Reply 3
Original post by Anonymous
its really confusing because I was taught to says bonds are overcome. SO can I say in a giant covalent structure the covalent bond is overcome hence the higher melting point/boilingpoint?


Bonds are overcome in everything except giant covalent -- they are broken in a giant covalent structure because this structure only contains covalent bonds between atoms, and the fact they have to be broken rather than being overcome is why they have such a higher MP/BP, because it requires a lot more energy to break a covalent bond than to overcome other forces
Reply 4
Original post by cyberhex
Bonds are overcome in everything except giant covalent -- they are broken in a giant covalent structure because this structure only contains covalent bonds between atoms, and the fact they have to be broken rather than being overcome is why they have such a higher MP/BP, because it requires a lot more energy to break a covalent bond than to overcome other forces


is this a level btw. so in a ionic bond you overcome the electrstatic attraction between ions hence breaking the ionic bond in simple covalent u overcome the estatic attraction between the molecules i.e. the intermolecular forces but in giant covalent you actually break the covalent bond when melting right?
Reply 5
Original post by Anonymous
is this a level btw. so in a ionic bond you overcome the electrstatic attraction between ions hence breaking the ionic bond in simple covalent u overcome the estatic attraction between the molecules i.e. the intermolecular forces but in giant covalent you actually break the covalent bond when melting right?


yep that's right :smile: and this applies to both GCSE and a-level
Reply 6
Original post by cyberhex
yep that's right :smile: and this applies to both GCSE and a-level


in something like NaCl are there vanderwaals forces between atoms?
Reply 7
Original post by cyberhex
Bonds are overcome in everything except giant covalent -- they are broken in a giant covalent structure because this structure only contains covalent bonds between atoms, and the fact they have to be broken rather than being overcome is why they have such a higher MP/BP, because it requires a lot more energy to break a covalent bond than to overcome other forces

Are there no intermolecualr forces between giant covalent also to make it clear you overcome tthe electostatic attraction when melting ionic compounds but do you actually break the ionic bonds or overcome them?
Reply 8
Original post by Anonymous
in something like NaCl are there vanderwaals forces between atoms?


Yep, pretty much all molecules have van der Waals forces because it's to do with changing electron density in the molecules, so you can generally assume any given molecule has them
Reply 9
Original post by Anonymous
Are there no intermolecualr forces between giant covalent also to make it clear you overcome tthe electostatic attraction when melting ionic compounds but do you actually break the ionic bonds or overcome them?

Giant covalent structures don't really have intermolecular forces because of their size, so when talking about melting/boiling points, you only have to consider the breaking of the covalent bonds between atoms.

Ionic bonds are generally described as being overcome because the electrostatic attraction is overcome, and that's all there is to an ionic bond - there isn't anything to break.
Reply 10
Original post by cyberhex
Giant covalent structures don't really have intermolecular forces because of their size, so when talking about melting/boiling points, you only have to consider the breaking of the covalent bonds between atoms.

Ionic bonds are generally described as being overcome because the electrostatic attraction is overcome, and that's all there is to an ionic bond - there isn't anything to break.

how about mettalic do you overcome the es attraction between the +ve metal ions and delocalised e-s, for ionic u overcome the es attraction between the ions, for simple covalent u overcome the intermolecular forces and for giant covelent u overcome the es attraction between the shared e-s and nuclei is that all correct?
Reply 11
Original post by Anonymous
how about mettalic do you overcome the es attraction between the +ve metal ions and delocalised e-s, for ionic u overcome the es attraction between the ions, for simple covalent u overcome the intermolecular forces and for giant covelent u overcome the es attraction between the shared e-s and nuclei is that all correct?

overcoming the es attraction between the shared e-s and nuclei in giant covalent breaks the covalent bond right?
Reply 12
Original post by Anonymous
how about mettalic do you overcome the es attraction between the +ve metal ions and delocalised e-s, for ionic u overcome the es attraction between the ions, for simple covalent u overcome the intermolecular forces and for giant covelent u overcome the es attraction between the shared e-s and nuclei is that all correct?

yep that's right :smile:
Reply 13
Original post by Anonymous
overcoming the es attraction between the shared e-s and nuclei in giant covalent breaks the covalent bond right?


I think so? I'll be honest, I've only ever been told that the shared electron pair is separated and the bond breaks
When boiling an ionic substance, you typically overcome the ionic bond rather than breaking it. Ionic bonds are formed through the electrostatic attraction between positively and negatively charged ions. When the substance is heated, the added energy increases the kinetic energy of the ions, causing them to move more rapidly. Eventually, the thermal energy becomes sufficient to overcome the attractive forces between the ions, leading to the separation of the ions and the conversion of the solid or liquid ionic compound into a gaseous state.

In the case of simple covalent compounds, such as molecules held together by covalent bonds, the boiling process involves overcoming the intermolecular forces between the molecules. Intermolecular forces, such as London dispersion forces, dipole-dipole interactions, and hydrogen bonding, are the attractive forces between neighboring molecules. When the compound is heated, the thermal energy increases, causing the molecules to move more rapidly. As the temperature approaches the boiling point, the kinetic energy becomes sufficient to overcome these intermolecular forces, leading to the conversion of the liquid into a gaseous state. So, in this case as well, the intermolecular forces are overcome rather than broken.
Reply 15
thank you both
Reply 16
Original post by cyberhex
Giant covalent structures don't really have intermolecular forces because of their size, so when talking about melting/boiling points, you only have to consider the breaking of the covalent bonds between atoms.


@typicalnerd is this correct when u boil/melt a giant covalent compound at A level do you overcome the electrostatic attraction between then [positive nuclei and shared electrons hence causing the bond to break? Or do you just say you overcome the electrostatic attraction between the electrons and nuclei and dont mention bond breaking at A level?

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