1. AS Chemistry prep - 2.3 ‘Intermolecular forces’
• This sheet of problems is designed to help you learn and understand the material we cover in
class.
• In addition to attempting these problems you should be reading around the topic, which is
covered by pages 160-169 in your textbooks.
• We will be spending several lessons on this topic before moving on, you may attempt these
problems at any point after we have started looking at 2.3 but I would like your completed
answers handed in at our first lesson on topic 2.7.
Exercise 1 - Key words
Find and explain the meanings of the following terms from this topic:
1. Intermolecular forces
2. Dipole
3. Enthalpy of vaporisation
Exercise 2 - Introduction to intermolecular forces
Explain the following using words and diagrams where appropriate:
1. Dipole-dipole interactions
2. London forces
3. Hydrogen bonds
Exercise 3 - What type of intermolecular forces?
Describe the intermolecular forces between molecules of:
1. Nitrogen (N2)
2. Hydrogen chloride (HCl)
3. Methanol (CH3OH)
4. Chloromethane (CH3Cl)
5. Octane (C8H18)
Exercise 4 - Textbook problems
Attempt the following questions from you textbook:
1. Questions 2 and 3 on page 163
2. Questions 1 and 2 on page 167
Exercise 5 - Solubility
1. Write yourself a set of ‘solubility rules’ to help you decide which solutes dissolve in which
solvents and which types of liquid are miscible (you may find page 168 useful)
2. The lattice enthalpy of calcium chloride is -2258 kJmol-1 and the enthalpy of hydration is +2378
kJmol-1. Would you expect calcium chloride to dissolve in water?
3. When sodium chloride is added to water it dissolves and a great deal of heat is produced.
What does this tell you about its lattice energy and hydration enthalpy?
Exercise 6 - Extension activities
1. Explain, in terms of intermolecular forces, why water actually becomes less dense below 4 °C
2. Watch this brief video clip from nature magazine about an amazing new ‘self-healing’ material
that relies on hydrogen bonding:
http://www.nature.com/nature/videoarchive/selfhealingrubber/