1. Henry R. Kang (1/2010)
General Chemistry
Lecture 1
Scientific Method

2. Henry R. Kang (1/2010)
Worlds of Chemistry
• Macroscopic World
 “Macro” means (1) large, (2) long, (3) inclusive
(American Heritage Dictionary)
 Macroscopic world is a world large enough that can
be seen, touched, and measured directly by human.
Examples: mass, volume, size, color, density, etc.
• Microscopic World
 “Micro” means small (American Heritage
Dictionary)
 Microscopic world is a world so small that cannot be
seen, touched, and measured directly by human.
Examples: atoms, molecules, ions, etc.

3. Henry R. Kang (1/2010)
Connection between Worlds of Chemistry
• Macroscopic and microscopic worlds are distinctively
different, yet intimately related.
 A macroscopic phenomenon is a concerted effect of members in the
underlying microscopic world.
• The understanding of the microscopic world relies on the
indirect measurements using modern technology and
scientific theories based on sound principles of mathematics,
physics, and chemistry.
• Results of chemical observations often come from the bulk
quantity of the macroscopic world, but the explanations often lie
in the microscopic world of unseen entities such as atoms,
molecules, and ions.
 Observations in macroscopic world
 Interpretations in microscopic world

4. Henry R. Kang (1/2010)
Scientific Method
• Scientific method is a systematic
approach to research & development.
 There is no one-size-fits-all method, but a
general approach falls into 3 stages:
• Initial stage
 Preliminary observations of a phenomenon
 Define the problem
 Tentative explanation: hypothesis
• Investigation stage
 Design and execute experiments
 Record results and analysis data
 Representation in the forms of symbols,
formulas, and equations
 Interpretation of the observed phenomenon
with hypothesis or theory
• Verification stage
 Analyze data for confirmation
 Perform further experiments
Observations
Interpretation
Problem Statement
Design Experiment
Results & Representation
Theory
Confirmation
Yes
No

5. Henry R. Kang (1/2010)
Experiment and Explanation
• An experiment is the careful
observations and measurements
of natural or scientific
phenomena carried out in a
controlled environment.
 The results must be able to
duplicate by others.
 Rational conclusions can be drew
to explain the observed phenomena
(interpretation or explanation).
Observation
Representation
Interpretation

6. Henry R. Kang (1/2010)
Record Information & Representation
• Information (data) Recording
 Qualitative data consist of general observations about the
system with coarse assessments without measured
quantifications
 Large or small, many or few, better or worse, present or absent, etc.
 Quantitative data comprise numerical quantifications
obtained by various measurements of the system.
 Numerical quantifications contain numbers and units.
 10.5 miles, 5 grams, etc.
• Representation
 A scientific shorthand for describing an experiment in
symbols and equations
 Chemical symbols: H2, O2, H2O, etc.
 Newton’s Law: F = ma

7. Henry R. Kang (1/2010)
Interpretation of Phenomena
• The interpretation of a phenomenon
has 3 levels
 Depend on the extent of verification
 Depend on the scope of the phenomenon
• Hypothesis
• Law
• Theory

8. Henry R. Kang (1/2010)
Interpretation by Hypothesis
• Hypothesis is a tentative explanation for a
set of observations.
• Further experiments are devised to test the
validity of the hypothesis in as many ways
as possible.
• Hypothesis that survives many
experimental tests of its validity may
evolve into law or theory.

9. Henry R. Kang (1/2010)
Interpretation by Law
• Law is the description of a fact that is
always the same under the same
conditions.
 Law usually is expressed in a concise statement or
mathematical formula (or equation).
 It describes a regularity of nature or a fundamental
relation between parameters.
• Example:
 Law of mass conservation.

10. Henry R. Kang (1/2010)
Interpretation by Theory
• Theory contains a body of knowledge such
as evidences, principles, and laws that
support this body of knowledge and
provide a unified explanation to a body of
phenomena in consistent with
observations.
• Examples:
 Big Bang theory (includes gravitational forces and
Doppler shift, which are laws)
 Molecular theory of gases.

11. Henry R. Kang (1/2010)
Verification
• Analyze data for confirmation.
• Negative results
 Modification or rejection of hypothesis
 Formulate new hypothesis
 Perform more experiments
• Positive results
 Support the hypothesis
 May become a theory or law

12. Henry R. Kang (1/2010)
Example: Big Bang Theory
• In 1940 George Gamow hypothesized that the universe began
with a gigantic explosion or “Big Bang”.
• Experimental supports
• The universe is indeed expanding as a result of explosion
• Red shift of spectra from far away stars, indicating that they are moving
away (Doppler effect).
• Cosmic background radiation
• Thermodynamic law shows that the temperature will be lower when
volume is expanded. After billions of years, the temperature of the universe
has cooled to 3 K, which most energy is in microwave region.
• Indeed, microwave signals have been recorded, and they are the same in
any direction.
• Primordial helium
• Small atoms such as hydrogen and helium were believed the first elements
formed.
• Helium atoms were found in a quasar about 10 billion light years away.