MP, BP - grphite and diamond

Both graphite and diamond form a network of strong covalent bond between
atoms and have a giant covalent structure. However, there is also van der
Waal's force formed between the graphite layers while it is not present in
diamond. Therefore, more energy is needed to melt graphite.This
explains diamond have lower melting point than graphite. Please notice that in
melting them, their structures need NOT to be broken down completely.

For the boiling point, the adjacent layers in graphite can be easily silde over
each other due to its weak van der Waal's force and 1 carbon atom only attachs
to 3 carbon atom while 1 carbon atom in diamond attachs to 4 carbon atoms to
form harder structure. When we need to overcome ALL the covalent bond to boil
them, diamond need more energy than graphite. This explains why diamond has
higher boiling point than graphite.

(I think this is NOT beyond the syllabus of HKDSE but detailed explaination is
not required. My explanation has simplified indeed. )

我印象中e個好似唔係DSE課程中，亦都唔需要知道，你只要記住e2隻同SiO2 係Ginat covalent structure就得同埋d properties