TEMA PARA LA MATERIA DE QUÍMICA...t/t

1. SCIENCE
QBA Miguel A. Castro Ramírez

2. Definition of Science
A way of exploring and explaining the natural
world
 Using a process designed to reduce the
chance of being misled

3. Scientific disciplines
 Branches of scientific knowledge that are
limited in size and scope to make them more
manageable.
 In reality, all branches of scientific knowledge
are inter-related and dependent on each
other
 Can you name some scientific disciplines?

4. Scientific disciplines
 All scientific disciplines are either:
1. Physical Science: study of matter
and energy
 Astronomy, geology, physics, and
chemistry
2. Biological Science: study of living
organisms
 Botany (plants) or Zoology (animals)
 See figure 1.1 in your book

5. Chemistry is a scientific discipline
 Concerned with the composition, structure
and properties of matter, as well as the
changes it undergoes during chemical
reactions
 Incorporates concepts of energy in relation to
chemical processes

6. Chemistry is a scientific discipline
 Itis fundamental to an
understanding of all
processes of the living state
 Biochemistry: the study of the
chemical processes of living
organisms

7. Chemistry is a scientific discipline
 Chemical processes produce
the products needed for our
clothes, housing,
transportation, medications
and recreational pursuits

8. Scientific disciplines
 The knowledge in separate scientific
disciplines combined create the whole of
scientific knowledge currently known.
 For example, knowledge of how the human
body works requires knowledge in the areas
of biology, chemistry, and physics.
 Can you think of some examples?

9. PART I:
SCIENTIFIC METHOD:
The process of science!!

10. The Scientific Method
 Make observations
 Ask questions
 Develop a hypothesis
 Make predictions
 Test the predictions
 Experiment
 Manipulate variables
 Independent
 Dependent
 Conclusions: analyze and
interpret results
 Peer Review/Publication
 The “scientific method” is a
formalized version of the procedure
any of us might take, using common
sense, to resolve a problem.
(Withgott and Brennan, 2007)

11. 1. OBSERVATION
The light doesn’t turn on

12. 2. QUESTION
Why didn’t the light turn on?

13. 3. MULTIPLE HYPOTHESES
What are all the possible
answers (hypotheses) to
the question?
Example: The light bulb is
burned out
Example 2: ?

14. 4. PREDICTIONS
What data would support a particular
hypothesis (= expected data) and/or
what data would refute the
hypothesis?
Example: The light bulb will rattle
when shaken

15. 5. TESTS (Experiments)
Conduct tests to collect actual data?
Example: Shake the light bulb and
record sound

16. 6. TENTATIVE CONCLUSIONS
Which hypotheses were supported
(not refuted) by the actual data?
Write up report (introduction,
methods, results, discussion) for
publication

17. 7. PEER REVIEW & PUBLICATION
Submit your report to a scientific journal that is
peer-reviewed, meaning that your methods, data,
tentative conclusions will be scrutinized by
scientists whose reputation is at stake if they allow
your report to be published.
Publication leads to creation of scientific information

18. The Scientific Method
 Scientific
understanding
advances through
evaluation and
dissemination of
information to the
scientific
community.
 How does this
information get
disseminated to the
public?
(Withgott and Brennan, 2007

19. PART II:
THE NATURE OF SCIENTIFIC
PROOF & KNOWLEDGE

20. Nature of scientific proof
 Hypothesis:
 A possible explanation or statement that might be
true and will be tested by the scientific method.
 Can be falsified
 Cannot be positively proven
 Therefore, hypothesis are accepted not proven

21. Nature of scientific proof
 Example:
 Observation: All the swans you have ever seen
are white
 Hypothesis: All swans are white
 Test: examine large number of swans
 Tentative conclusion: all swans are white
(hypothesis accepted)
 If you looked at a million white swans, there
could still be a black one
 However, if you found just one black swan,
your hypothesis would be falsified

22. Nature of scientific proof
 When a hypothesis withstands RIGOROUS
testing, especially over time, it becomes a
theory
 Theory:
 A hypothesis that has been rigorously tested and
over time has become generally accepted by the
scientific community as correct

23. Nature of Scientific Proof
 Some examples of theories are:
 Theory of relativity
 Theory of plate tectonics
 Theory of evolution
 Eventually theories become laws
 Law of gravity

24. Nature of Scientific Knowledge
 The main body of science is very stable and
grows by being corrected slowly
 So, although scientists accept that scientific
knowledge is always open to improvement,
the main body of knowledge is well-accepted
and stable

25. Nature of Scientific Knowledge
 Scientific fact
 A valid observation about some natural
phenomenon obtained by carrying out
experiments
 Scientific theory:
 A hypothesis that has been tested and validated
over a long period of time
 Theory of evolution

26. Nature of Scientific Knowledge
 Scientific
law: generalization that
summarizes facts about natural phenomena
 Law of gravity
 Scientific law vs scientific theory:
 Law addresses how it behaves
 Theory addresses why it behaves that way

27. Scientific Worldview
 Thereare several beliefs underlying the
work of scientists:
 By working together over time, people can
figure out how the world works
 Knowledge is both stable and changing
 Scientists become excited by new ideas, but are
skeptics that judge ideas by the strength of the
evidence that supports them.

28. Scientific Worldview
 The universe is a unified system
 functions in accordance with fixed natural laws that do not
change from time to time or from place to place
 Knowledge gained from studying one part of it can often be
applied to other parts of it
 All events arise from some cause or causes and, in
turn, cause other events.
 We can use our senses and reasoning abilities to
detect and describe natural laws that underlie the
cause and effect relationships we observe in nature.

29. Are the terms
Science and Technology
synonymous?

30. Science ≠ Technology
Technology = the application of
scientific knowledge for
practical purposes.

31. PART III:
EXPERIMENTAL DESIGN

32. Experiments--definition
A well-defined, controlled procedure for
obtaining information about a system
under study
 A way to test an hypothesis

33. Experiments—some rules
1. Adequate Sample Size. Ex. Larger sample size better
2. Representative Sample. Ex. Random sample

34. Manipulative or controlled
study
 Uses a model system to control and manipulate variables
 An experiment in which variables are taken into account
 Based on comparing a control group with an experimental
group
 Both groups are treated identically except for one variable or
factor
 This factor is changed for the experimental group but not the
control group
 If an effect is seen in the experimental group but not the
control group that indicates that the factor changed is the
cause of the effect

35. Examples of Controlled
Studies
 Studying the effect of nutrients on plant
growth—add or change the kinds & amounts
of nutrients in natural or artificial setting
 Studying the effect of grazing on plant
communities—exclude grazing on study plots
& allow grazing on others
 Challenge: hard to do over large scales of
space & time

36. Controlled study
 Variables:factors that affect observations
or experiments
 Dependent variable—response that is
measured
 Independent variable—varied or manipulated
by researcher (cause)

37. AN EXAMPLE OF A
CONTROLLED STUDY
THE MEALWORM MYSTERY

38. MEALWORM MYSTERY
 A student conducted 4 experiments to determine
how mealworms respond to light and moisture.
 All variables except light and moisture were held
constant from experiment to experiment.
 For each experiment, 12 mealworms were placed
in the center of a box and then their positions
were recorded 24 hours later.

39. EXPERIMENT 1
mealworm
QUESTION: Are mealworms attracted to
light?
QUESTION 2: Are mealworms affected by
moisture?
Answer? You can’t tell; it could be either
or both

40. EXPERIMENT 2
QUESTION: Are mealworms affected by
light?
QUESTION 2: Are mealworms affected by
moisture?
Answers? They are affected by light; we
don’t know about moisture

41. EXPERIMENT 3
QUESTION: Are mealworms affected by
light?
QUESTION 2: Are mealworms affected by
moisture?
Answers? With just this experiment, it
seems they didn’t move

42. EXPERIMENT 3
Using the
information
from the
other 2
experiments…
QUESTION: Are mealworms affected by
light?
QUESTION 2: Are mealworms affected by
moisture?
Answers? Yes and Yes (despite attraction
to light, they avoided wet

43. THE EXPERIMENTS
1 mealworm 2
3 Without the
controlled
experiment we
would know
nothing!
QUESTION: Which variables affect mealworm movement based on the
above experiments (note that movement may be either toward or away
from something)? A. Light but not moisture. B. Moisture but not light. C.
Both light and moisture. D. Neither light nor moisture. E. Can’t tell.