# An unknown liquid occupies a volume of 5 ml and has a mass of 40 grams. How do you find the density?

##### 1 Answer

#### Explanation:

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)|)))#