Section 3 - Intermolecular bonding

Question 1

Some compounds are made up of ‘simple molecules’. What are they?

Answer 1

These are just groups of a few atoms joined together by covalent bonds. For example, water or oxygen.

Question 2

What are intermolecular bonds

Answer 2

Very weak forces of attraction that form between molecules

Question 3

What does the strength of intermolecular bonds affect?

Answer 3

Boiling points

Question 4

When simple molecular substances melt or boil, is it the covalent bonds or the intermolecular bonds that get broken?

Answer 4

Intermolecular bonds

Question 5

What are the two things that can affect the strength of intermolecular forces?

Answer 5

1) The number of electrons in a molecule: the more electrons there are, the stronger the intermolecular bonds between molecules.
2) The surface area of the molecule: the larger the surface area over which intermolecular bonds can act, the stronger the intermolecular bonds between molecules.

Question 6

Use the idea of intermolecular bonds to explain the trend in boiling points of alkenes increasing in size (exam q)

Answer 6

• There is a clear trend showing that as the molecules get larger their boiling point increases.
• This is due to the fact that the larger molecules have a greater surface area, so there is stronger intermolecular bonding. The larger molecules also have more electrons - this further increases the strength of the intermolecular bonds between molecules.