Hydrogen Bonding

When does hydrogen bonding happen?

When hydrogen is covalently bonded to fluorine, nitrogen or oxygen

Why does hydrogen have a high charge density?

It's small and fluorine, nitrogen and oxygen are very electronegative

When the bond is so polarised, what will form?

A weak bond forms between the hydrogen of 1 molecule and a lone pair of electrons on the fluorine, nitrogen or oxygen in another molecule

What do molecules that have hydrogen bonding usually contain?

OH or NH groups

What does hydrogen bonding have a huge effect on?

The properties of substances

What are the properties of hydrogen bonding?

Soluble in water and have higher boiling and melting points than molecules of a similar size that are unable to form hydrogen bonds.

What do water and ammonia have and why?

Very high boiling points if you compare them with other hydrides in their groups, because of the extra energy needed to break the H bonds

How are the molecules in ice held together?

In a lattice by hydrogen bonds

What happens when you melt ice? (1)

Hydrogen bonds are broken, so ice has more hydrogen bonds than liquid water

What happens when you melt ice? (2)

Since hydrogen bonds are relatively long, the molecules in ice will, on average, be further apart than in liquid water, which makes ice less dense than liquid water.