Density for Kids: How Much Stuff Is Packed Into a Space? (Grade 6 and Grade 7 Science)

Hi, I'm Luna from DoodleBeez. Why does a huge log float, while a tiny pebble sinks? The answer is density. Today we will learn how much stuff is packed into a space, and how to calculate it.

Density compares mass to volume. Mass is how much matter something has. Volume is how much space it takes up. Picture two boxes the same size. The one with more particles packed inside is denser.

To find density, divide the mass by the volume. If mass is in grams and volume is in cubic centimeters, the answer is in grams per cubic centimeter. Pure water has a density of about one.

Let's try one. A block has a mass of thirty grams and a volume of ten cubic centimeters. Thirty divided by ten is three. So the block has a density of three grams per cubic centimeter.

Density predicts sinking and floating. An object less dense than water floats, like wood or ice. An object denser than water sinks, like a pebble or a coin. Oil is less dense than water, so it floats on top.

Density does not depend on size. Cut a gold bar in half, and each half has the same density as the whole bar. Because each pure substance has its own density, scientists can use it to identify materials.

Now it's your turn. A toy has a mass of twenty grams and a volume of forty cubic centimeters. What is its density, and will it float in water? Pause and try. Zero point five, so it floats!

Great job! Remember, density is mass divided by volume. Things less dense than water float, denser things sink, and density stays the same however big the piece. Practice density in the Science Lab at doodlebeez.com. See you next time!