6. diamond and graphite are both composed of carbon atoms. the density of diamond is 3.52g/cm3. the density of graphite is 2.25g/cm3. in 1955, scientists successfully made diamond from graphite. using the relative densities imagine what happens at the atomic level when this change occurs. then suggest how this synthesis may have been accomplished.

They have different quantity of atoms in the same volume, due to a difference in pressure and temperature, that is the process to obtain diamond.  

Explanation:

Since the subatomic particles are the ones that give mass (specially the nucleus), so in the same volume (the same space), there are different quantity of atoms.

When scientist study both materials, they discover that the atoms arrangements are different. In diamond, there are in a tetrahedral shape, so the atoms are closer, that is also the reason for the hardness of this material. In graphite, in the other hand, the atoms are in layers, so the atoms are "spread" apart, and also this is the result to have a softness texture.

To obtain diamond from graphite, is necessary to apply high pressure and temperature, so the atoms can move and rearrange to have the new geometrical shape.

it is b that is the answer.