Between ALL molecules, whether polar or not. VERY WEAK forces between very small,TEMPORARY dipoles
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Permanent Dipole-Dipole.
In POLAR molecules. The PERMANENT dipole of one molecule ATTRACTS to the permanent dipole of another molecule. This forms a WEAK permanent dipole-dipole force.
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Hydrogen Bonding.
Strong DIPOLE-DIPOLE attraction between an ELECTRON DEFICIENT HYDROGEN atom on one molecule and a LONE PAIR of electrons on an ELECTRONEGATIVE atom on another molecule.
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Water Properties
- Ice is less dense than water: as there is an OPEN LATTICE where the hydrogen bonds hold the water molecules APART. - High melting/boiling point: As the hydrogen bonds are EXTRA forces over VDW so need more ENERGY.
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How are Van der Waals' forces caused?
- MOVEMENT of electrons on shells. This UNBALANCES distribution of CHARGE. Causes INSTANTANEOUS dipole across molecule. This INDUCES a dipole in a neighbouring molecule etc. The small induced dipoles ATTRACT each other = Van der Waals'.
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Other cards in this set
Card 2
Front
Permanent Dipole-Dipole.
Back
In POLAR molecules. The PERMANENT dipole of one molecule ATTRACTS to the permanent dipole of another molecule. This forms a WEAK permanent dipole-dipole force.
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