H1D - Intermolecular Forces

Question 1

As the mass of atoms increase so too does the temperature at which they boil increase. Why is this?

Answer 1

The bigger the atom the more energy it takes to break the Van der Waal forces keeping the atoms together as a liquid

Question 2

When is it thought that Van der Waal forces occur?

Answer 2

When the electrons in atoms move randomly forming slight dipoles, these slight dipoles can cause dipoles in other atoms and a brief attraction occurs but then breaks as the electrons continue to move

Question 3

What are slight dipoles?

Answer 3

Where one side of the atom is positive and the other negative

Question 4

What affect does the number of electrons have on the size of potential dipoles

Answer 4

The more electrons there are the bigger the potential dipole and the stronger the Van der Waal force.

Question 5

Bigger atoms require more energy to move - what affect does this have on breaking Van der Waal forces?

Answer 5

Bigger atoms require more energy to move and so more energy is required to get the atoms going fast enough to break the Van der Waal forces between them.

Question 6

Describe dipoles and Van der Waal forces within non-polar molecules

Answer 6

The dipoles within this type of molecule are daubed by the random movement of the electrons and are called London dispersion forces. they are the weakest type of attraction.

Question 7

When do non-polar molecules occur?

Answer 7

Non-polar molecules occur when the atoms within the molecule have similar or equal electronegativities or, if there are polar bonds that are symmetrically opposed.

Question 8

Since polar bonds arise when there is a difference in electronegativity between two bonded atoms, what affect does this have on the bonding electrons and thus on dipoles?

Answer 8

The bonding electrons are closer to one atom than the other. The arising dipole is permanent and therefore the arising Van der Waal forces are stronger than the London dispersion force caused by temporary dipoles. This type of Van der Waal force is called a permanent dipole/permanent dipole interaction

Question 9

Explain the trend in boiling points going down the halogen group?

Answer 9

it increases as the bigger the atom the bigger the temporary dipole exists thus increasing the LDF