Answer 1

Diamond	Graphite
It has a crystalline lattice.	It has a layered structure
In diamond, each carbon atom is sp3 hybridised and is bonded to four other carbon atoms through a σ bond.	In graphite, each carbon atom is sp2hybridised and is bonded to three other carbon atoms through a σ bond. The fourth electron forms a π bond.
It is made up of tetrahedral units.	It has a planar geometry.
The C–C bond length in diamond is 154 pm.	The C–C bond length in graphite is 141.5 pm.
It has a rigid covalent bond network which is difficult to break.	It is quite soft and its layers can be separated easily.
It acts as an electrical insulator.	It is a good conductor of electricity.

Answer 2

Since diamond exists as a three-dimensional network solid, it is the hardest substance known with high density and high melting point.

Whereas in graphite, any two successive layers are held together by weak forces of attraction. This makes graphite soft.

In graphite, carbon atom is sp2 hybridized whereas in diamond, carbon atom is sp3 hybridized.

Unlike diamond, graphite is good conductor of heat and electricity.