[3] “What is a theory?

·        A theory provides a general explanation for observations made over time.

·        A theory explains and predicts behaviour.

·        A theory can never be established beyond all doubts.

·        A theory may be modified.

·        Theories seldom have to be thrown out completely if thoroughly tested but sometimes a theory may be widely accepted for a long time and later disproved.” (Dorin H, Demmin P E, Gabel D, Chemistry: The Study of Matter, Englewood Cliffs, NJ: Prentice Hall, Inc.)