6.4 Hydrogen bonding

define a hydrogen bond

a type of permanent dipole-dipole interaction found between molecules containing an electronegative atom with a lone pair of electrons and a hydrogen atom attached to an electronegative atom

explain why ice is less dense than water

1) when water freezes hydrogen bonds hold water molecules apart in an open lattice structure 2) the water molecules in ice are further apart than in water

benefits of ice being less dense than water in lakes and ponds

the ice acts as an insulating layer and prevents the water from freezing solid

explain why water has a relatively high melting and boiling point

1) all molecules have London forces between them 2) hydrogen bonds are extra forces over and above the London forces 3) a larger quantity of energy is required to break hydrogen bonds in water