Students are introduced to the idea that matter is composed of atoms and molecules that are ... experiment with and observe the heating and cooling of a solid, liquid, and gas.

Mysterious dark matter makes up 85 percent of matter in the universe, and of the remaining 15 percent, scientists couldn’t account for half—until now.

Astronomers tallying up all the normal matter—stars, galaxies and gas—in the universe today have come up embarrassingly short ...

The universe's missing matter may have finally been found.Astronomers think regular matter — that is, the stuff that isn't ...

Their volume stays the same. Examples of gases include steam, helium and oxygen. They are often invisible. They do not have a fixed shape. They spread out and change their shape and volume to fill ...