This lesson plan is intended to be a guide to see how a demonstration might fit in to the lesson, information wise. This lesson plan does not contain the modes of how to teach, rather a suggested outline of information.
Students will:

know the various intermolecular forces and their strengths

identify which IMF a molecule has

rank molecules in order of IMF strength

draw the interactions of multiple molecules of a compound
Background Knowledge Assumed

students can determine if a molecule is polar or not
Engage
Do the demonstration Bending Water and review polarity with students.
Explore
Have students work in pairs to determine the number of drops a penny can hold for each of the
4 solvents (water, ethanol, acetone, pentane). Then have them determine how much time it takes for 1 drop to evaporate. The IMF Lab is attached.
Explain
Have students share the data that they got. Ask students what they notice about the molecules that can hold more drops on the penny and take longer to evaporate. They should notice that those molecules have oxygen and are therefore polar. It’s those characteristics that determine the type of intermolecular forces a molecule can have.
All molecules have London dispersion forces (Van der Waals) due to the movement of electrons. As electrons move around the nucleus, they aren’t always distributed evenly, causing somewhat of a charge distribution. Slightly positive sides of a molecule are attracted to the slightly negative sides of another molecule. This is the weakest intermolecular force.
Dipole-dipole forces occur between molecules that are polar. In polar molecules the electrons are unevenly distributed because some elements are more electronegative than others. The partial negative side of one molecule is attracted to the partial positive side of another molecule.
This type of force is stronger than London dispersion forces because polar molecules have a permanent uneven distribution of electrons.
Hydrogen bonding is a misnomer, as it is also an intermolecular force and not a bond. It is the strongest intermolecular force. It is a special kind of dipole-dipole interaction that occurs when a hydrogen atom is bonded to fluorine, oxygen, or nitrogen. (Remember it by: hydrogen bonding http://sites.jmu.edu/chemdemo
JMU Department of Chemistry and Biochemistry

is FON). Because hydrogen doesn’t hold its electrons closely, it has a partial positive and fluorine, oxygen or nitrogen are partially negative. The oppositely charged sides of the molecules are attracted to one another.
Extend
Now that students know the different intermolecular forces, have them complete their lab sheet, identifying the intermolecular forces present in each solvent and answering the questions.
Students can circle, triangle, and/or box the locations on the solvent molecules that the intermolecular forces will act.
Evaluate
As a formative assessment to ensure that students understand the material, have them do the exit ticket below to hand in before they leave class. http://sites.jmu.edu/chemdemo
JMU Department of Chemistry and Biochemistry

IMF Lab
Water
H
2
O
Structural Diagram
H
O
H
Name _________________________
London
Dispersion
Forces (O)
Dipole-
Dipole
(∆)
Hydrogen
Bonding
(  )
# of Drops on Penny
Time for 1
Drop to
Evaporate
Ethanol
CH
3
CH
2
OH
H
H H
C C O
H H
H
O
Acetone
CH
3
COCH
3
Pentane
C
5
H
12
H
3
C
H
C
H
H
C
C
H H
C
CH
3
C
H
H
H H H H H
1. Which type of IMF is predominant in water? Why?
2. Which type of IMF is predominant in pentane? Why?
3. Which type of IMF is predominant in acetone? Why?
4. Place the solvents (liquids) in order of increasing IMF. Explain your reasoning.
5. Did your data support your answer to number 4?
6. On the back of this sheet draw how 4 molecules of water would interact. Do the same for ethanol and acetone.

IMF – Exit Ticket
Substance
Polar or
Nonpolar
London
Dispersion
Forces
Dipole-Dipole
Forces
Hydrogen
Bonding
Think about intermolecular forces and intramolecular forces. Which are stronger? Why?
Substance
Polar or
Nonpolar
London
Dispersion
Forces
Dipole-Dipole
Forces
Hydrogen
Bonding
Think about intermolecular forces and intramolecular forces. Which are stronger? Why?