Question

An irregular solid with a mass of 45.0 g was dropped into and sank to the bottom of a graduated cylinder containing water. The initial volume of the water was 50.0 mL, and the final volume was 70.0 mL. What is the approximate density of the irregular solid?

Answer 1

The answer is 2.25g/ml or 2.25 g/cm³

To do this, you need to know the formula of density. Density is the mass per unit of volume. 

$D= \frac{M}{V}$

Where:
D = Density
M = Mass
V = Volume

You already have your mass, which is 45.0g, so what is your volume?

A graduated cylinder measures the volume of liquids. The procedure that was done here is called the displacement method. You can get an estimated volume of an irregular object by subtracting the initial volume from the final volume. 

In this case, it would be:

70.0mL - 50.0mL = 20.0 mL

The volume is then 20.0mL. 

Now that we have the volume we can solve for density. 

$D= \frac{45.0g}{20.0mL}$

$D= 2.25\frac{g}{mL}$

Now take note that 1mL = 1cm³. So you can also express the answer as

2.25g/cm³.