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Factors that affect the strength of London Forces
1) The more protons and electrons in a molecule, the
stronger the London Forces
-(higher molar mass usually means stronger
London Forces)
2) A molecule with a linear shape will have stronger
London Forces than a molecule with a spherical
shape (if p+ and e- are the same)
What type of IMF are in the following molecules?
CH3OH
CH3Cl
CBr4
CI4
H2
H2O
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Other Properties Affected by
Intermolecular Forces:
Surface Tension:
(The attraction of molecules to each other on a liquid's surface)
Relationship:
Volatility of Liquids: (How easily they evaporate)
Relationship:
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Viscosity of Liquids: (Their resistance to flow)
Relationship:
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Ionic Compounds do not have intermolecular
forces
• When you melt an ionic compound you are
breaking the attractive forces between ions
Comparing the Strength of Intermolecular
and Intramolecular Forces
Ionic Bond Covalent Bond
Hydrogen Bond
Dipole Dipole Forces
London Forces
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page 69
- 5-7
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3) methane is polar so it has dipole forces while
methane is non-polar so it has London forces only.
Dipole forces are stronger than London forces so it takes
more energy to separate the molecules (which is what
happens when something boils
4) The stronger the intermolecular force the higher the
melting and boiling point
5) Test the conductivity of the solid and the solution
-the metal will conduct as a solid
-the ionic compound will conduct in solution
-the molecular compound will never conduct
6) Ionic compounds are hard, so they are hard to shape
Ionic compounds are brittle so they break when force is
applied
7)
a) The compound appears to be molecular so it should
have a low melting point
b) The atoms are connected by covalent bonds
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