4. Topics in physics.
5. Scientific habit of thought.
6. Value of relating new ideas to former experiences.
7. Hypothesis.
8. Theory.
9. Law.
(2) The States of Matter
4. Physics Defined.—In the study of any science or field of knowledge, it is helpful to have a basis for grouping or classifying the facts studied. In physics we are to study the objects, forces, and changes about us, to understand them and their relations to one another. Accordingly, physics, dealing with the material world about us, is often defined as the science of matter and energy, matter being anything that occupies space and energy the capacity for doing work. This definition of physics while not strictly accurate is sufficiently comprehensive for our present purpose.
5. The Three States of Matter.—Our bodies are matter since they occupy space. Further, they possess energy since they are able to do work. In beginning the study of physics it will simplify our work if we study one of these topics before the other. We will therefore begin with matter and consider first its three states.