WA.4. Physical Science
PS2. Matter: Properties and Change
6-8.PS2. Atoms and Molecules: In prior grades students learned the scientific meaning of the word matter, and about changes of state. In grades 6-8 students learn the basic concepts behind the atomic nature of matter. This includes the idea that elements are composed of a single kind of atom. Atoms chemically combine with each other or with atoms of other elements to form compounds. When substances are combined in physical mixtures, their chemical properties do not change; but when they combine chemically, the new product has different physical and chemical properties from any of the reacting substances. When substances interact in a closed system, the amount of mass does not change. Atomic theory also explains the ways that solids, liquids, and gases behave. These concepts about the nature of matter are fundamental to all sciences and technologies.
6-8.PS2B. Students know that mixtures are combinations of substances whose chemical properties are preserved. Compounds are substances that are chemically formed and have different physical and chemical properties from the reacting substances.
6-8.PS2B.2. Students are expected to demonstrate that the properties of a compound are different from the properties of the reactants from which it was formed.