 Density is basically how tightly packed atoms are. Mathematically, density is mass/volume. In other words, it is how heavy something is, divided by how much space it takes up. If you think about atoms as marbles (which we know they’re not from the last lessons but it’s a useful model), then something is more dense if its marbles are jammed close together.

For example, take a golf ball and a ping pong ball. Both are about the same size or, in other words, take up the same volume. However, one is much heavier, has more mass, than the other. The golf ball has its atoms much more closely packed together than the ping pong ball and as such the golf ball is denser.

This experiment builds on the Play With Your Food experiment, so we’ll be learning more about density.  Are you ready?

### 4 Responses to “Pile It In”

1. Lesa Junek says:

Thank you!

2. Yes mass is in grams or kg (kilograms). Ounces can be tricky since it’s a measure of volume and also mass. Fluid ounce is volume, and ounce is mass. Density is mass per unit volume, so kg per m3 is common. You can also have:

kilograms per liter (kg/L)
grams per milliliter (g/mL)
metric tons per cubic meter (t/m3)
kilograms per cubic decimetre (kg/dm3)
grams per cubic centimetre (g/cm3)
1 gram/cm3 = 1000 kg/m3
megagrams (metric tons) per cubic metre (Mg/m3)
pounds per cubic foot (lb/cu ft)
pounds per cubic yard (lb/cu yd)
pounds per US liquid gallon (lb/gal)
pounds per US bushel (lb/bu)
slugs per cubic foot

3. Lesa Junek says:

We just figured out the water should be in ml to “match” the grams of the mass. But, we’d still like to know the proper way to express units of density.

Thanks!

4. Lesa Junek says:

The mass would be in grams. When we measure the water, is this in ounces? What is the unit of measurement for density?
Thank you,
Lesa