Students observe and discuss water on the molecular level using the idea that water is composed of tiny molecules that are attracted to one another.

Students investigate how low temperature causes water vapor to condense into a liquid and then freeze to form a solid.

Explore molecular motion and attraction, and see how those phenomena affect the matter they comprise.

One way scientists talk about matter or substance-that is, the stuff in the world-is in terms of pure substances and mixtures. Pure substances are substances that contain only one kind of molecule. Water with nothing else in it is a pure...