Lecture #1 – The Nature of Chemistry Chemistry 142 B James B. Callis, Instructor Winter Quarter, 2006

Chemistry The branch of science that deals with the properties of substances and the reactions that transform them into other substances. Chemistry is a central science. Chemistry uses the scientific method to advance its knowledge.

Chemistry Oceanography Atmospheric Sciences Economics Physics Medicine Governments Geology Anthropology Biology Astronomy Politics People Chemistry As a Central Science

Definitions Law – a summary of observed behaviors. Hypothesis – a possible explanation of an observation or set of observations. Theory – A set of tested hypothesis that gives an overall explanation of some natural phenomenon or phenomena.

The Scientific Method Information or data is gathered by careful observation of the phenomenon being studied. On the basis of that information a preliminary generalization or hypothesis is formed. A series of experiments is devised to test the predictive power of the hypothesis.

The Scientific Method (cont.) (a)Accepted as scientific theory. (b) Modified so that all results are adequately explained. (c) Discarded. On the basis of the experimental tests, the hypothesis may be

Making Observations Formulating Hypothesis Extracting Predictions From the Hypothesis Performing Experiments Components of the Scientific Method

The Modern Science Paradigm

Paths of Science Deduction - going from the general to the particular. An intermediate step, simulation, is often taken. The "easy" way. Induction - going from the particular to the general. The "hard" way.

Hallmarks of a Good Theory It explains the deficiencies of previous theories, and/or subsumes them. It has predictive power. In chemistry, it explains macroscopic phenomena in terms of atomic and molecular phenomena. It is elegant and simple.

Example: 19th Century Physics vs. 20th Century Physics Classical Mechanics of Newton vs. Quantum Mechanics of Schrödinger

Remember: The #1 job of a scientist is to rule out hypotheses. "The great tragedy of Science - the slaying of a beautiful hypothesis by an ugly fact." - T.H. Huxley

What Happened To The Balloon? It was wimpy and broke. It was fearful of all of the people. It got zapped by Klingons. Hydrogen burns!

2H 2 (g) + O 2 (g) = 2H 2 O (g) + Energy Hydrogen and oxygen are diatomic gases. Water can be a gas. ENERGY was released -- This is characteristic of an exothermic reaction. This is a balanced chemical reaction.

Chemistry 142 A: Professor Callis Text: Chemical Principles - By Steven S. Zumdahl Chapter 1 : Keys to the Study of Chemistry Chapter 2 : Atoms, Molecules and Ions Chapter 3 : Stoichiometry: Mole - Mass Relationships in Chemical Systems Chapter 4 : The Major Classes of Chemical Reactions Chapter 5 : Gases and the Kinetic - Molecular Theory Chapter 6 :Chemical Equilibrium Chapter 7 : Acids and Bases Chapter 8 : Applications of Aqueous Equilibria

Chemistry Homework Linus Pauling “ Chemistry is not a spectator sport. You must become involved. And that means that you must do homework!”