Discovering Intermolecular Forces (IMFs)

Mrs. B-Z

pp. 189-193 in your text may be of some help

1.  Intermolecular forces (IMFs) occur between ______molecules. Remember molecules refer to elements that have been bonded ______.

2.  Intramolecular bonds occur ______a molecule between the ______. These are ______than IMFs.

3.  As far as intramolecular bonds there are four main types

  1. Strongest (usually has highest boiling point) bond is the ______which occurs because there is a sea of ______. Example(s): ______These (Circle one: do or do not) have IMFs.
  2. Next strongest intramolecular bond is usually ______which occurs between a ______(positive ion) and a ______(negative ion). Example(s): ______These (Circle one: do or do not) have IMFs.
  3. Second weakest intramolecular bond is usually the ______which occurs between two or more ______which form a ______moment (slightly positive and slightly negative ends) due to the fact that the electrons are being shared ______. Example(s): ______These (Circle one: do or do not) have IMFs.
  4. The weakest intramolecular bond is the ______which occurs between two ______which ______electrons ______. Example(s): ______These (Circle one: do or do not) have IMFs.

4.  When boiling a ______substance, one is trying to overcome the ______not the bonds. This is why we study IMFs of covalent molecules.

5.  IMFs directly influence the ______of a substance. The ______the IMF, the ______the ______.

6.  There are three main types of intermolecular forces (IMFs)

a) ______

b) ______

c) ______

7.  The IMF called ______or ______occurs in all molecules but it is the weakest force.

If you are trying to determine which substance would have the higher ______and both of them have ONLY this type of force then you compare the ______of the two substances. The substance with the ______mass has the stronger IMF.

Diagram of dispersion or London forces acting between atoms of methane

8.  The IMF called ______occurs between two identical ______molecules. This force is stronger than ______but weaker than ______.

Diagram of dipole-dipole interactions between atoms of hydrochloric acid

9.  The IMF called ______occurs between identical molecules that have two characteristics. First they must contain ______AND they must have that ______directly bonded to an atom of ______, ______, or ______. Always keep in mind that this is a ______not a ______as the name is a misnomer.

Diagram of hydrogen bonding between atoms of water.

How to Determine the IMFs Present in a Molecule

Decision Tree

Examples for you to try

1.  List ALL of the IMFs present in hydrofluoric acid and draw a diagram of the strongest interaction.

2.  List ALL of the IMFs present in carbon tetrachloride and draw a diagram of the strongest interaction.

3.  List ALL of the IMFs present in boron tetraiodide and draw a diagram of the strongest interaction.

4.  List ALL of the IMFs present in carbon dioxide and draw the strongest interaction.

5.  Predict which molecule would have the stronger IMF C6H6 or CH4? Show proof for your reason.

6.  Predict which molecule would have the stronger IMF NH3 or Br2? Show proof for your reason.

7.  Predict which molecule would have the higher boiling point SO2 or H2O? Show proof for your reason.

8.  Predict which molecule would have the higher boiling point Ar or O2?

9.  Predict the type of intramolecular bond present for each molecule or element (assume it is bonded to another atom of itself) and decide which has the highest (1) and lowest (4) boiling point.

Substance / Type of intramolecular bond and IMF if present (covalent molecules only) / Assign relative value of boiling point from 1(highest) to 4 (lowest)
Cu
NaCl
PH3
C3H8

8