Students will understand that...

Matter of any type can be subdivided into particles that are too small to see, but even then the matter still exists and can be detected by other means. The amount (weight) of matter is conserved when it changes form, even in transitions in which it seems to vanish. Measurements of a variety of properties (e.g., hardness, reflectivity) can be used to identify particular materials.

AND

When two or more different substances are mixed, a new substance with different properties may be formed; such occurrences depend on the substances and the temperature. No matter what reaction or change in properties occurs, the total weight of the substances does not change.