# What is the density of a substance if a sample of 375 mL has a mass of 450 grams?

Jan 15, 2016

$\text{1.2 g/mL}$

#### Explanation:

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

$\textcolor{b l u e}{\text{density" = "mass"/"unit of volume}}$

This means that your goal when asked to find a substance's density will be to find the mass of one unit of volume of that substance.

In your case, the sample is said to have a volume of $\text{275 mL}$. This means that the unit of volume will be $\text{1 mL}$. So, you must use the information provided to determine the mass of $\text{1 mL}$ of your substance.

Well, you know that a volume of $\text{375 mL}$ of this substance has a mass of $\text{450 g}$. Since density is essentially a measure of how the atoms that make up a substance are packed per unit of volume, you can safely assume that it will be constant for a substance as long as temperature and pressure are kept constant.

This means that you can write

1 color(red)(cancel(color(black)("mL"))) * "450 g"/(375 color(red)(cancel(color(black)("mL")))) = "1.2 g"

So, if $\text{1 mL}$ of your substance has a mass of $\text{1.2 g}$, you can say that its density will be equal to

"density" = rho = "1.2 g"/"1 mL" = color(green)("1.2 g/mL") -> rounded to two sig figs