Let’s say you have a brick and a piece of Styrofoam that are exactly the same size. Which one weighs more? Chances are, you said the brick weighs more but do you know why? It’s all about density.

Fun Science Facts for Kids All about the Density

Fun Science Facts for Kids All about the Density

Fun Facts

  • The density of an object is determined by two things: the mass of the molecules in the object, and how tightly packed the atoms are together.
  • A brick has high density because it is made from molecules that have a lot of mass. The atoms are packed closely together.
  • Styrofoam is low density. The molecules in Styrofoam don’t have a lot of mass. The atoms are loosely packed with lots of holes and air between them.
  • Density and buoyancy are interconnected. Which object is likely to float, the brick or the Styrofoam? You’re right if you guessed the Styrofoam. Low density objects will float on a material that is higher in density (such as water).
  • Think of other materials that are low or high density. Wood, cork, and sponges are all low-density materials. So are most natural materials, such as pumpkins, peppers, or pine cones. Cement, metal, and glass are high-density materials.


  1. Density: refers to the mass of the molecules in a material and how tightly the atoms in the material are packed together
  2. Low-density: materials containing molecules with less mass and atoms that are loosely packed
  3. High-density: materials containing molecules with more mass and atoms that are tightly packed


Question and Answer
Question: Why does density matter?
Answer: Understanding density can help you predict whether or not something will float. This matters a lot of you want to float down a creek and you’re choosing a flotation device.

Learn More
Did you know that some liquids are denser than others? Some liquids can float on top of others. Head over to PBS to learn more.