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[http://cwx.prenhall.com/bookbind/pubbooks/mcmurry2/medialib/fig10.gif]
[http://ds9.ssl.berkeley.edu/LWS_GEMS/2/images_2/pom535.jpg]
InterIntermolecular Forcesmolecular Forces
• Forces of attraction between two or more molecules.
• Can help determine how a chemical changes between a solid, liquid, or gas.
[http://cwx.prenhall.com/bookbind/pubbooks/hillchem3/medialib/media_portfolio/text_images/CH11/FG11_01.JPG]
Intermolecular ForcesIntermolecular Forces
• Hydrogen Bonding
• Occurs in molecules where F, N, or O are bonded to an H atom.
• Strongest of the “forces”
[http://www.saburchill.com/IBbiology/chapters01/images/11010328.jpg]
Highest boiling points
[http://cwx.prenhall.com/bookbind/pubbooks/hillchem3/medialib/media_portfolio/text_images/CH11/FG11_21.JPG]
Intermolecular ForcesIntermolecular Forces
• Dipole – Dipole Force
• Force that attracts polar molecules to one another.
• Only occurs in polar molecules
• Moderate “force”
[http://darkwing.uoregon.edu/~ch111/images/electroneg.gi]f
Electronegativity Values
Remember – Elements that are more electronegative “pull” the electrons in a
bond closer
H
H
OO OC
Polar vs. Nonpolar
[http://wps.prenhall.com/wps/media/objects/602/616516/Media_Assets/Chapter10/Text_Images/FG10_04.JPG]
[http://cwx.prenhall.com/bookbind/pubbooks/mcmurry2/chapter10/medialib/TB10_002.JPG]
Intermolecular ForcesIntermolecular Forces
• Dispersion Forces• Since electrons are
always moving they could temporarily concentrate on one side of a molecule.
• These occur in all molecules.
• Weakest of the “forces”[http://www.chem.unsw.edu.au/coursenotes/CHEM1/nonunipass/HainesIMF/images/dispersion.jpg]
[http://wps.prenhall.com/wps/media/objects/602/616516/Media_Assets/Chapter10/Text_Images/FG10_TB03.JPG]
Heavier mass = Stronger Dispersion Force
[http://cwx.prenhall.com/bookbind/pubbooks/mcmurry2/chapter10/medialib/TB10_005.JPG]
Comparison of the Forces
Intermolecular ForcesIntermolecular Forces
• Example:
• Which intermolecular forces are present in NH3 molecules?
Intermolecular ForcesIntermolecular Forces
• Dispersion Forces
• Dipole-Dipole Forces (it is polar!)
• Hydrogen Bonding (N-H bonds!)
[http://www.wackyscienceguy.com/khemistry/fall/covalent/quiz/images2/polaritynh3.jpg]
Intermolecular ForcesIntermolecular Forces
• Example:
• Which intermolecular forces are present in CH4 molecules?
Intermolecular ForcesIntermolecular Forces
• Dispersion Forces only!
[http://www.wackyscienceguy.com/khemistry/fall/covalent/quiz/images2/polaritynh3.jpg]
Intermolecular ForcesIntermolecular Forces
• Example:
• List the following from lowest melting point to highest melting point:
• CO2 (g), O2 (g), N2(g)
Intermolecular ForcesIntermolecular Forces
• All only have Dispersion Forces so…
• N2 (g) : 28.0 g/mol (lowest)
• O2 (g) : 32.0 g/mol
• CO2 (g) : 44.0 g/mol (highest)
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