6.3 - Intermolecular forces

Question 1

What are intermolecular forces?

Answer 1

Weak interactions between dipoles of different molecules

Question 2

What are the three main categories of intermolecular forces?

Answer 2

• Induced dipole-dipole interactions (London forces)
• Permanent dipole-dipole interactions
• Hydrogen bonding

Question 3

What are London forces?

Answer 3

Weak intermolecular forces that exist between all molecules, whether polar or non-polar

Question 4

How are induced dipoles formed?

Answer 4

1. Movement of electrons produce a changing dipole in a molecule
2. At any instant, an instantaneous dipole will exit, but its position is constantly shifting
3. The instantaneous dipole induces a dipole on a neighbouring molecule
4. The induced dipole induces further dipoles on neighbouring molecules, which then attract one another

Question 5

Are induced dipoles temporary or permanent?

Answer 5

Temporary

Question 6

What does an increase of electrons do in each molecule?

Answer 6

• Larger instantaneous and induced dipoles
• Greater induced dipole-dipole interactions
• Stronger attractive forces between molecules