What is the precise nature of chemical processes and what drives them will be the questions we endeavor to touch upon in this and next semester. The answer to why chemistry occurs lies in the fact that at normal energy/temperature scales, the so called ``electromagnetic'' force, which is responsible for the charge-charge interactions described above, dominates. Electrostatic forces are responsible for the structure and dynamical behavior of atoms and molecules. The modern-day quantum theory of these interactions (which will be introduced next semester) can, in principle, predict the properties of atoms, molecules and aggregations of these into macroscopic matter. However, exact solutions of the theory for nearly all systems is intractable, and it becomes necessary to construct models and approximations.
This brings up the importance of the interplay between theory and experiment. Without theory, science would be just a vast catalogue of experimental results bearing no relation to each other and having no apparent rationalization. Theoretical analysis gives a deeper understanding of experimental findings by providing interpretation, connection to other experimental results, and prediction of experimental outcomes. However, theoretical predictions or hypotheses must be subject to vigorous experimental scrutiny before they can become statements of scientific law or accepted theories. Likewise, without experiment, science would be just a collection of untestable hypotheses. Even when a theoretical hypothesis become scientific law, if enough experimental evidence emerges that contradicts the statement, it might be necessary to ammend or discard that law in favor of another. There have only been a few instances of this in the history of science, and these have often resulted in scientific revolutions (e.g., Galileo's planetary model, Newton's laws of classical mechanics, the quantum theory, and Einstein's special and general relativity theories).