Intermolecular Forces

Question 1

What are intermolecular forces

Answer 1

These are the forces of attraction between molecules or substances and need to be broken when a substance is melted or boiled

Question 2

What are the 3 main types of intermolecular forces

Answer 2

Vander Waals (VW)
Dipole-dipole attraction
Hydrogen bonds

Question 3

What are vander waals

Answer 3

These are temporary induced dipole-dipole attraction. They are the weakest intermolecular force.

Question 4

How do VW occur

Answer 4

These occur due to temporary dipoles inducing a temporary dipole in another molecule, the dipoles can then attract

Question 5

What 2 factors depend for the strength of vander waals

Answer 5

1) number of electrons( more electrons means there are higher chances of a temporary dipole occurring)
2) surface area( longer the surface area the greater the chance of uneven distribution of electons)

Question 6

How are dipole-dipole attractions(permanent dipole-dipole attraction) formed

Answer 6

This is formed when there is a difference in electronegativity( stronger than vander waals)

Question 7

Why might a molecule not be a dipole even though it contains a permanent dipole

Answer 7

This is because a molecule can be symmetrical therefore the dipoles will cancel each other out.

Question 8

How do hydrogen bonds occur

Answer 8

It occurs because of permanent dipoles between N and H, O and H, F and H.
(Strongest type of intermolecular force)

Question 9

Why is the volume of ice greater than the same mass of water

Answer 9

In ice water molecules stop moving therefore the hydrogen bonds become fixed. Hydrogen bonds are longer than covalent bonds, this gives ice an open structure.

Question 10

How can the strength of hydrogen bonding be observed

Answer 10

This can be done by looking at the boiling points of hydrides of groups 4,5,6 and 7