Question

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

Answer 1

`"8 g mL"^(-1)`

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 `"5 mL"`.

This should automatically tell you that one unit of volume is equal to `"1 mL"`.

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 mL"`

`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)|)))`