Answer
d = 2.65 $\frac{g}{mL}$
Work Step by Step
To find the density of quartz, apply the formula:
d = $\frac{m}{V}$
We know the m of quartz piece 38.4 g.
To find the volume we subtract the volume of water from the volume of water and quartz after the quartz was submerged into water.
$V_{quartz}$ = 65.7 mL - 51.2 mL
$V_{quartz}$ = 14.5 mL
2- Now we replace the volume of quartz into density formula:
d = $\frac{m}{V}$
d = $\frac{38.4 g}{14.5 mL}$
d = 2.65 $\frac{g}{mL}$