This week we’ll look at density. Density is a measurement of how solid something is. Specifically it is the mass per unit volume of a substance. If you have two objects of the exact same size (volume), the more dense object will weigh less than the less dense object.
So there are two things contributing to density:
- The mass of the atoms or molecules that makes up the material.
- The volume or amount of space the material takes up. If the molecules or atoms are “packed” in more closely, it will be more dense.
For example, styrofoam is a low density material. Even a large styrofoam container does not weigh much. The molecules in the styrofoam do not have much mass and there is a lot of space between them. A brick, on the other hand, is much more dense. Even a moderate sized brick can be pretty heavy. This is because the molecules which make up the rock have more mass and are packed more closely together.
Density and buoyancy are closely related. A less dense substance will float on a more dense substance.
Younger students studying this topic will appreciate this book: What Is Density? (Rookie Read-About Science for ages 6 and up)
Older students can learn more about density from this Wikipedia article.This article is part of the Density and Buoyancy series. See the list below for links to the other articles in this series.