AS Chemistry - Intermolecular Forces

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What is a dipole?
Where the bonded electron pair is shared unequally between the bonded atoms
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What is an instantaneous dipole?
Movement of electrons (uneven distribution) producing a temporary dipole in a molecule (constantly shifting)
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What is an induded dipole?
A dipole formed due to it being next to an instantaneous dipole (i.e. the instantaneous dipole induces a dipole in the neighbouring molecule)
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What are induced dipole-dipole interactions?
Weak intermolecular forces that exist between all molecules, whether polar or non-polar
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What are Van Der Waals?
Used to describe both induced dipole-dipole and permanent dipole-dipole intermolecular forces
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What is a hydrogen bond?
A special type of permanent dipole-dipole interaction found between molecules containing an electronegative atom with a lone pair of electrons (e.g. nitrogen, oxygen or fluorine) and a hydrogen attached to an electronegative atom in another molecule
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How do London forces arise between iodine molecules?
Iodine is a non polar molecule. - Temporary dipole forms in one molecule due to uneven distribution of electrons. - Induces a dipole in a neighbouring molecule. - Dipoles attract each other.
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What happens when there are more electrons in a molecule?
The larger the instantaneous and induced dipole. The stronger the attractive force between them. The more energy is then needed to overcome the intermolecular forces
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Why are molecules with hydrogen bonds harder to break?
Hydrogen bonds are the strongest intermolecular force.
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What bonds form hydrogen bonds?
O, F and N atoms are the only atoms electronegative enough to form H-bonds
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Why is ice less dense than water?
When water freezes the water molecules can’t move about and the hydrogen bonds hold the molecules in fixed positions. The 3D structure created resembles the structure of diamond. In order to fit into this structure the molecules have to be less tight
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What is the solubility of simple covalent structures in an organic substance?
Soluble. Weak Van der Waals between hexane molecules can be overcome. Van der Waals form between substance and hexane molecules
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Other cards in this set

Card 2

Front

What is an instantaneous dipole?

Back

Movement of electrons (uneven distribution) producing a temporary dipole in a molecule (constantly shifting)

Card 3

Front

What is an induded dipole?

Back

Preview of the front of card 3

Card 4

Front

What are induced dipole-dipole interactions?

Back

Preview of the front of card 4

Card 5

Front

What are Van Der Waals?

Back

Preview of the front of card 5
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