GENERAL
CHEMISTRY
I
DARYLL T. CAGOYONG
Instructor
How did people in
ancient times know what
to use for soap, perfumes,
metal refining, medicines
and etc.?
 Describe the approaches used by the
ancient Greek philosophers to
understand the world around them.
 Define deductive and inductive
reasoning.
 Name key individuals and groups who
contributed to the science of
chemistry.
 Describe the scientific method.
 Describe the rise and fall of phlogiston
theory.
• Developed some powerful methods of acquiring
knowledge.
• Known for their love of wisdom “PHILOSOPHY”
• Was
the
approach
answering
questions
the world.
basic
in
about
• Was the best way
to
answer
fundamental
questions.
 THALES of Miletus (625-545 BC) – believed that
water was the fundamental unit of matter.
 Anaximenes (585 – 525 BC) – felt that air was the
basic unit of matter.
 Empedocles (490-430 BC) – argued for the idea that
matter was composed of earth, air, fire, and water.
• Ideas
of matter
were put forth but
could
not
be
proven
or
disproven.
 Assumed four fundamental substances of matter : air,
water, fire, and earth.
 First major philosopher to gather data thru
observation.
 Could potentially be considered the first “real”
scientist because of his systematic observations of
nature before trying to understand what he was
seeing.
 Recorded many observations in the field of astronomy,
meteorology, biology, and optics.
 Was refuted by Leucippus and Democritus of his
proposed theories about matter.
• Deductive & Inductive Reasoning
• Hypothesis, Theories, & Laws
INDUCTIVE REASONING
DEDUCTIVE REASONING
 From specific to general.
 From general to specific.
 E.g.
 E.g.
"The coin I pulled from the bag is a
penny. That coin is a penny. A third
coin from the bag is a penny.
Therefore, all the coins in the bag
are pennies."
"All men are mortal. Picolo is a
man. Therefore, Picolo is mortal."
• Wild/genius guess.
• a supposition or
proposed
explanation made on
the basis of limited
evidence as a
starting point for
further investigation.
• Tentative
explanation of the
natural law.
• a model or way of looking
at nature that can be used
to explain natural laws and
make further predictions
about natural phenomena.
When differing or
conflicting theories are
proposed, the one that is
most successful in its
predictions is generally
chosen. Also, the theory
that involves the smallest
number of assumptions—
the simplest theory—is
preferred.
• Answers to “why’s”
• Phlogiston Theory suggested that flammable
materials tended to weigh less after being burned.
• Phlogiston – substance that is lost from a
material when it is burned; burning up.
Put forth in
1667
SUPPORTS
 Burning of wood—ashes
remains weigh less than the
original wood sample.
(dephlogisticated- the remains)
CONTRADICTS
 Mercury experiment of Lavoisier—
when mercury was heated it would
become mercuric oxide and would
gain weight.
 When mercuric oxide was heated,
it returned to mercury and
released gas he identified as
oxygen.
 Later the theory was replaced
by the oxygen-based
combustion.
• A concise
statement—always
true, often in
mathematical form,
about natural
phenomena.
• combination of
observation,
experimentation,
and the
formulation of laws,
hypotheses, and
theories.
• Developed by
Francis Bacon but
was later modified.
1. Ask a question.
2. Do background research.
3. Form a hypothesis.
4. Test the hypothesis.
5. Collect, Organize and Analyze
the
Data.
6. Draw Conclusions.
7. Communicate the results.
STEP 1: ASK A QUESTION / OBSERVATIONS
 Observations based on senses or
tools
 Sight, Smell, Touch etc.
 Observations of natural events
usually raise a question
 Why did the water rise when the
candle went out?
 Research is usually done to help find
out more about the question raised
 The scientific method starts when you
ask a question about something that
you observe: How, What, When, Who,
Which, Why, or Where?
 Rather than starting from scratch in
putting together a plan for
answering your question, you want
to be a savvy scientist using library
and Internet research to help you
find the best way to do things and
ensure that you don't repeat
mistakes from the past.
For a help in this step, use these
sources:
 Background Research Plan
 Finding Information
 Bibliography
 Research Pape
 Based on your observation a
Hypothesis is formed that tries
to explain your observation or
answer your question
 A hypothesis tries to predict or
determine the outcome of your
experiment even before the
experiment is done
 Predictions usually stated in an “if …..
Then” statement. Ex: If I drop a rock
then it will fall down toward the
ground
 HYPOTHESIS MUST BE
TESTABLE!
 Controlled Experiments are used to test a
hypothesis
 A controlled experiment is an experiment
that tests only one factor at a time by
 a control group is compared with an
experimental group. Variables are not
changed in the Control Group.
 Control groups allows you to see if a
change in a variable creates an observed
outcome by comparing the control group
with the exp. grp
 A variable is a factor that changes in a
controlled experiment. Variables are
changed in the Exp. Group AND
SERVE AS THE FACTOR TESTED.
 INDEPENDENT
 The variable being changed in the
experiment
 DEPENDENT
 The variable that responds to the
changed independent variable
 The variable being measured
 EX: growing plants with different
amounts of fertilizer
 Scientists try to design
experiments that will clearly show
whether a particular VARIABLE
caused an observed outcome.
 IF IT CANNOT BE OBSERVED
THEN IT CANNOT BE
TESTED!!!
 Can we test if a comet impact kill the
dinosaurs? Why or Why Not?
 Sometimes models are used to
represent a real object
 Used when it is difficult to control all
of the variables or not possible to
test “the real thing”
Variables are not
Changed in C.G.
One Variable Changed in
Each Exp. Group
 Data collected from
experiments
 Data is defined as: recorded
observations or measurements
(qualitative = description,
quantitative = number data)
 Based on observations
 Utilize tools or senses: sight,
smell, temperature change etc.
 Data is organized in tables,
charts and graphs so that it
can be more easily analyzed
 Scientists decide whether the
results of the experiment
support a hypothesis.
 When the hypothesis is not
supported by the tests the
scientist must find another
explanation for what they have
observed
 NO EXPERIMENT IS A FAILURE: All
experiments are observations
of real events
 Results must be communicated
in the form of a written paper
or presentation
 Communication helps other
scientists performing the same
experiments to see if the
results of your experiment are
the same as their results
 Helps people see if results are
repeatable!
Get a paper and make a
scientific method you’ve
done in your life.