Density and Volume

If you hold a bowling ball and a volleyball of the same size, the bowling ball feels heavier. Why is that? It’s due to a concept called density, which describes how tightly particles are packed in a substance.

The bowling ball's tightly packed solid plastic particles make it denser, while the air-filled volleyball is much less dense.

To compare densities, we need to know the volume—the space an object occupies.

For regular shapes like boxes, volume is calculated by multiplying length, width, and height.

However, finding the volume of irregular shapes, like keys or toys, can be trickier. This is where the water displacement method helps.

For instance, if you drop a key into a graduated cylinder and the water level rises from 4 milliliters to 4.8 milliliters, the key’s volume is 0.8 milliliters.

Now, with mass and volume, density can be calculated as mass divided by volume.

For example, if a volleyball with a mass of 300 grams has a volume of 600 cubic centimeters, its density is 0.5 grams per cubic centimeter.