Students are introduced to the idea that matter is composed of atoms and molecules that are attracted to each other and in constant motion. Students explore the attractions and motion of atoms and ...

Even when liquids change their shape, they always take up the same amount of space. Their volume stays the same. Examples of gases include steam, helium and oxygen. They are often invisible.

Water is the only substance on Earth that occurs naturally as a solid, liquid ... one or two forms of matter into other forms—for example, converting carbon dioxide gas into solid carbon ...