Density Lesson for Kids: Definition & Facts

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  • 0:03 Understanding Density
  • 1:01 Finding Mass and Volume
  • 2:32 Examples of Density
  • 4:37 Lesson Summary
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Lesson Transcript
Instructor: Emily Lockhart

Emily has taught science and has a master's degree in education.

In this lesson, we will look at the definition of density, which can be used to describe everyday objects. We will also look into the density of a few objects and observe density in real life.

Understanding Density

Pillow fights are a lot of fun. Pillows are usually filled with soft, fluffy stuffing, like feathers. Feathers are ideal for pillow fights because they have a low density - they don't hurt much when you swing a pillow filled with them at your friend. In this lesson, we will learn about density and observe the density of objects like feathers, cotton candy and bricks.

Density is a word we use to describe how much space an object or substance takes up (its volume) in relation to the amount of matter in that object or substance (its mass). Another way to put it is that density is the amount of mass per unit of volume. If an object is heavy and compact, it has a high density. If an object is light and takes up a lot of space, it has a low density.

So, if we know the volume and mass of an object, we can calculate the density using the equation density = mass / volume.

The formula for density

Finding Mass and Volume


How do we go about finding those two properties of matter? Let's start with mass, which we've learned is a measurement of the amount of matter in an object or substance. Mass is very important because it's a universal measurement - it's used by scientists all over the world and even astronauts on the International Space Station. That's because, unlike weight, mass doesn't change due to changes in gravity. A huge block of ice, for example, weighs much less in space because of lower gravity, but its mass is always the same.

Mass is measured in grams (expressed as g) and kilograms (expressed as kg). We typically use a balance to measure mass, but we can also find mass by measuring the Earth weight of an object with a weight scale. Then, scientists can calculate the mass by applying a complex formula that divides the weight by the force of gravity.


Volume - how much space an object or substance takes up - is measured in cubic meters, but you'll more commonly see it in the simplified form of liters (expressed as L) and milliliters (mL). We often use measuring cups (like the ones in your kitchen!) to find out how much volume a substance has, though we can also find the volume of an object by measuring its sides.

We would say a couch has more volume than a chair, because a couch takes up more space. Imagine your bathtub filled with sand and your bathroom sink filled with sand - the bathtub sand would have a lot more volume (would take up a lot more space) than the sink sand.

Examples of Density

Let's practice our newfound knowledge of density to find and compare the density of common objects.

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