An unknown liquid occupies a volume of 5 ml and has a mass of 40 grams. How do you find the density?
The thing to remember about density is that its purpose is to express the mass of one unit of volume of a given substance.
In other words, in order to find a substance's density, you must determine the exact mass of one unit of volume. In this case, the volume of the sample is said to be equal to
This should automatically tell you that one unit of volume is equal to
So, you essentially know the mass of five units of volume, since
#"5 mL" = 5 xx "1 mL"#
which means that all you have to do now is use the information given as a conversion factor to find the mass of
#1 color(red)(cancel(color(black)("mL"))) * "40 g"/(5 color(red)(cancel(color(black)("mL")))) = "8 g"#
You can thus say that the density of this liquid is equal to
#color(green)(bar(ul(|color(white)(a/a)color(black)("8 g"/"1 mL" = "8 g/ mL" = "8 g mL"^(-1))color(white)(a/a)|)))#