Macromolecules have very high melting and boiling points as a lot of energy is required to break the strong covalent bonds between the atoms in a macromolecule covalent lattice in order for the compound to melt or boil unlike simple covalent molecules which have low melting and boiling points.
Example: Diamond has a melting point of 3550 degrees Celcius and a boiling point of up to 4827 degrees Celcius.
Most macromolecules do not have mobile particles to conduct electricity. However, graphite is able to as there are delocalised electrons between the layers.
(the electrons are in between the layers)Diamond is one of the hardest substances known as its structure consists of a giand 3D covalent lattice of tetrahedrally bonded Carbon atoms where each carbon atom is covalently bonded to 4 other Carbon atoms. The strong lattice system of covalent bonds is thus hard to break making diamond a extremely hard substance often used for cutting.
The forces between the layers of hexxagonal lattices in graphite is very weak hence layers can slip over each other easily making graphite a good lubricant.
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