Density

physics · mass · volume · materials

What density means. Density is how much stuff (mass) is squeezed into a certain amount of space (volume). Think of it like this: a bowling ball and a beach ball might be the same size, but the bowling ball has way more stuff packed into it, so it's much denser.

Why things sink or float. Objects that are denser than water sink, while objects less dense than water float. A rock is super dense and sinks, but wood is less dense and floats because it has more air pockets inside.

The density formula. Scientists write density as the symbol ρ (rho), and it equals mass divided by volume. If you know how much something weighs and how much space it takes up, you can calculate exactly how dense it is.

Same stuff, different densities. Even the same material can have different densities depending on how it's packed. Ice is less dense than liquid water, which is why ice floats on top of water in a glass.

Density in real life. Density helps scientists figure out what materials will work best for different jobs. Ships are made of steel because even though steel is super dense, the ship's shape creates air spaces that make the whole thing less dense than water.