# What is the density of a substance that has a mass of 2.7 g and a volume of 35 mL?

Dec 19, 2015

$\rho = \text{0.077 g/mL}$

#### Explanation:

As you know, density is defined as mass per unit of volume.

That means that every time you're asked to find the density of a substance, you have to determine the mass of one unit of volume of that substance.

In this case, the volume is given to you in milliliters, $\text{mL}$, so one unit of volume will be equal to $\text{1 mL}$.

So, how would you go about finding the mass of $\text{1 mL}$ of this substance?

Density is essentially a measure of how well the atoms of a given substance pack per unit of volume. The important thing to realize about density is that every unit of volume will pack the same number of atoms, i.e. will have the same mass.

This means that you can use the fact that a volume of $\text{35 mL}$ corresponds to a mass of $\text{2.7 g}$ to figure out the mass you'd get per milliliter

1 color(red)(cancel(color(black)("mL"))) * "2.7 g"/(35 color(red)(cancel(color(black)("mL")))) = "0.077 g"

So, if $\text{1 mL}$ of this substance has a mass of $\text{0.077 g}$, then its density is

$\rho = \textcolor{g r e e n}{\text{0.077 g/mL}}$