Mercury, which is often used in thermometers, has a density of 13.534 g/mL at room temperature. What volume of mercury contains 10.0 g?
A substance's density basically tells you how much mass of said substance occupies one unit of volume.
In your case, the density of mercury is given in Grams per milliliter,
So, mercury is said to have a density of
You want to know the volume of mercury that will contain
You can use dimensional analysis using the density of mercury as a conversion factor
#10.0color(red)(cancel(color(black)("g"))) * overbrace("1 mL"/(13.534color(red)(cancel(color(black)("g")))))^(color(purple)("given density")) = color(green)(|bar(ul("0.739 mL"))|)#
The answer is rounded to three **sig figs, the number of sig figs you have for the mass of your sample.