Matter is anything that has mass and volume.
To understand changes in matter, you need to know what the sample of matter was like before the change and what it is like after the change. You also need to be able to describe and classify matter.
States of Matter:
Any kind of matter can be classified as a
mixture or a pure substance.
Mixture--matter that has two or more kinds of particles and thus may have different properties in different samples
Pure substance--a substance that has the same properties in any sample you choose. There are two kinds of pure substances: elements and compounds.