# 2.3 The Density of A Solid

Density calculations for regular solids are very simple. As with all density calculations, you need to know both the volume of the object, and its mass. Finding the volume of regular solids (solids of a recognizable form: cube, rectangular prisim, etc..) is very easy because you can measure the sides and calculate the volume using a formula (see apendix: Formulae). Finding the Volume of an irregular solid is more difficult. You must use water displacement to find the volume of an irregular solid. (for instructions see chapter 1.4: Experimentation). For this experiment, take the objects your teacher gives you, and find their density by using the formula D=M/V.

## Calculating and converting

When converting densities (a mass divided by a cubic length (such as kg/m3)), remember to include the cubic nature of the length.

Q: How many cubic meters in a cubic kilomter?

A: While a kilometer is 1000 (1x3) meters, a cubic kilometer is equivalent to one million cubic meters (1x109 m3), because there are three sides of 1000 meters that make a cubic kilometer, and volume is calculated from length x length x length, or in this case 1000 x 1000 x 1000 = 1x109.

### Equivalencies

When comparing certain metric cubic volumes, they will be equivalent when both units for length and mass are changed together. So in this case 1 kg/m3 will equal 1 g/cm3.