How does the crystalline structure of graphite compare with that of diamond?

1) In diamond, each carbon is tetrahedrally attached to another carbon with covalent bonds and the carbons are sp3 hybridized. In graphite, each carbon is connected to three other carbons with a trigonal planar shape, which forms a sheet of carbon. All the sheets are connected to each other with dispersion forces. Each carbon in graphite is sp2 hybridized.

2) Because it is one of multiple forms of carbon.

3) Amorphous solid

4) Molecular solid because you only have to break off the intermolecular forces which is relatively weak, as opposed to ionic solids where you have to break off electrostatic attraction which is a very strong force.

5) Ice. A crystal possesses rigid and long-range order; its atoms, molecules, or ions occupy specific positions.

Crystalline Structure Of Graphite

Graphite is in sheets. Graphite is layered, and while there are strong bonds between the graphite atoms in the sheets, the sheets themselves are held by weak forces. Diamonds, on the other hand, have a three dimensional lattice network, of very strong bonding forces between each atom.

http://www.edinformatics.com/interactive_molecules...

Allotropes are defined as different forms of an elementary substance. So different forms of carbon atoms.

Peanut brittle would be consider an amorphous solid.

For 4, consider salt (ionic solid) and sugar (molecular solid). I think you can figure out which one melts at a much lower temperature.

A crystalline solid is an orderly array or atoms or molecules. So both salt and sugar are crystals.

Salt (NaCl) is an orderly array of sodium and chloride atoms (face centered cubic). And sugar (sucrose) is a crystal in an orderly array of sugar molecules. It is monoclinic, P21 space group.

I'll add that diamond can form cubic or, occasionally, hexagonal crystals.

Peanut brittle would be a composite, which is organic structures held together buy the uncrystallized sugar. The sugar could be amorphous or vitreous (glass-like).