Untitled - Kelly Walsh High School

Intermolecular Forces, Solids and Liquids 167
atoms in methane. The polarity of the polar covalent carbon-fluorine bond is not
equal to that of a carbon-hydrogen bond. This difference in polarity means that
the bond polarities will no longer cancel. If the bond polarities do not cancel, the
molecule is polar. Methyl fluoride is a polar molecule. The strongest intermolecular
force in the polar methyl fluoride is a dipole-dipole force.
The krypton atom in krypton difluoride does not obey the octet rule. The presence
of five pair around the krypton leads to a trigonal bipyramidal electron-group
geometry. The presence of three lone pairs and two bonding pairs around the krypton
makes the molecule linear. The two krypton-fluorine bonds are polar covalent.
However, in a linear molecule, the bond polarities pull directly against each other
and cancel. Cancelled bond polarities make the molecule nonpolar. The strongest
intermolecular force in the nonpolar krypton difluoride is London force.
The answers are:
Methane, CH 4, London force
Methyl alcohol, CH 3OH, hydrogen bonding
Diamond, C, covalent bonding
Methyl fluoride, CH 3F, dipole-dipole force
Iron, Fe, metallic bonding
Ammonium fluoride, NH 4F, ionic bonding
Krypton difluoride, KrF 2, London force
Sodium chloride, NaCl, ionic bonding
In this chapter, you have learned about intermolecular forces, the forces
between atoms, molecules, and/or ions. The types of intermolecular forces
include ion-dipole forces, hydrogen bonding, ion-induced and dipole-induced
forces, and London (dispersion) forces.
Liquids possess certain properties due to the intermolecular forces between the
liquid particles. These properties include surface tension, viscosity, and capillary
action. Solids may be either amorphous or crystalline in nature.
A phase diagram may represent changes of state in a substance. The critical
point is the point beyond which the gas and liquid states are indistinguishable
while the triple point is the point of a phase diagram in which the solid, liquid
and gas may all exist.
1. Which of the following is not an example of a change of state?
a. melting b. freezing c. burning d. boiling e. subliming
2. Ion-dipole forces exist in which of the following?
a. NaCl(s) b. KNO 3(s) c. CH 3OH(l) d. NaCl(aq) e. HCl(g)