3.4: Intermolecular forces

Question 1

List the intermolecular forces from weakest to strongest.

Answer 1

Dispersion forces
Dipole-dipole bonds
Hydrogen bonds

Question 2

What are dispersion forces?

Answer 2

• ALL types of molecules
• Non-polar molecules ONLY have dispersion forces

Question 3

Properties of dispersion forces?

Answer 3

1. Larger molecules have more electrons (more forces)
2. Shape of molecule (long chain will have more dispersion forces than compact molecules)

Question 4

What are dipole-dipole forces?

Answer 4

• Only in POLAR molecules
• permanent dipoles rather than instantaneous, temporary

Question 5

Properties of dipole-dipole forces?

Answer 5

The stronger the dipole-dipole forces, the higher the melting/boiling points. More energy required to break bonds + change states.

Question 6

What is hydrogen bonding?

Answer 6

• occurs between hydrogen that is covalently bonded to HOF.
• more energy to break bond as hydrogen is weakly electronegative, bonded to an element with higher EN (polarity of bond is much greater)

Question 7

How to structure answers?

Answer 7

1. Polarity of each compound
2. Intermolecular forces
3. Strength of bonds
4. Energy required to break bonds