# Problem: Amorphous silica, SiO2, has a density of about 2.2 g/cm3, whereas the density of crystalline quartz, another form of SiO2, is 2.65 g/cm3 . Which of the following statements is the best explanation for the difference in density?(a) Amorphous silica is a network-covalent solid, but quartzis metallic.(b) Amorphous silica crystallizes in a primitive cubic lattice.(c) Quartz is harder than amorphous silica.(d) Quartz must have a larger unit cell than amorphoussilica.(e) The atoms in amorphous silica do not pack as efficientlyin three dimensions as compared to the atoms in quartz.

###### FREE Expert Solution

amorphous → no definite structure or form, irregularly shaped solid

Crystalline quartz highly structured, crystalline solid made of silica, SiO2

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###### Problem Details

Amorphous silica, SiO2, has a density of about 2.2 g/cm3, whereas the density of crystalline quartz, another form of SiO2, is 2.65 g/cm3 . Which of the following statements is the best explanation for the difference in density?

(a) Amorphous silica is a network-covalent solid, but quartz
is metallic.
(b) Amorphous silica crystallizes in a primitive cubic lattice.
(c) Quartz is harder than amorphous silica.
(d) Quartz must have a larger unit cell than amorphous
silica.
(e) The atoms in amorphous silica do not pack as efficiently
in three dimensions as compared to the atoms in quartz.