Density

Density tells us how much matter is squished into a space. Some things are packed tight and feel heavy. Others are loose and feel light. A rock has high density. A piece of foam has low density.

Understanding Density

Think of a small box full of marbles and another box full of feathers. The marble box weighs more, even if both boxes are the same size. That is because marbles have more density than feathers. Density is about how heavy something is for its size. It helps us understand why some things feel heavy and others do not.

Density and Water

Density explains why some things float and others sink. Things less dense than water, like wood, float. Things more dense than water, like rocks, sink. Oil is less dense than water, so it floats on top. This is why oil and water do not mix well.

Fun Facts

• Gold is one of the most dense metals on Earth.
• Ice is less dense than water, which is why ice cubes float.
• The planet Saturn is so low in density it could float in a giant bathtub.

Did You Know?

A spoonful of material from a neutron star would weigh as much as a mountain because it is so dense.