Section 1.3 Scientific Methods

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Section 1.3 Scientific Methods

• Identify the common steps of scientific methods.

• Compare and contrast types of data.
• Identify types of variables.
• Describe the difference between a theory and a
  scientific law.

systematic approach an organized method of
solving a problem.
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Section 1.3 Scientific Methods (cont.)
scientific method qualitative data quantitative
data hypothesis experiment independent variable
dependent variable control conclusion theory scien
tific law
Scientists use scientific methods to
systematically pose and test solutions to
questions and assess the results of the tests.
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A Systematic Approach

• The scientific method is a systematic approach
  used in scientific study, whether it is
  chemistry, physics, biology, or another science.

• It is an organized process used by scientists to
  do research, and provides methods for scientists
  to verify the work of others.

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A Systematic Approach (cont.)

• The steps in a scientific method are repeated
  until a hypothesis is supported or discarded.

Form a question
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A Systematic Approach (cont.)

• An observation is the act of gathering
  information.

• Qualitative data is obtained through observations
  that describe color, smell, shape, or some other
  physical characteristic that is related to the
  five senses.
• Quantitative data is obtained from numerical
  observations that describe how much, how little,
  how big or how fast.
• What are some qualitative observations you could
  make in this room? What are some quantitative
  observations?

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A Systematic Approach (cont.)

• A hypothesis is a tentative explanation for what
  has been observed. (An educated explanation for
  a problem).

• An experiment is a set of controlled observations
  that test the hypothesis.

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A Systematic Approach (cont.)

• A variable is a quantity or condition that can
  have more than one value.

• An independent variable is the variable you plan
  to change.
• The dependent variable is the variable that
  changes in value in response to a change in the
  independent variable.

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A Systematic Approach (cont.)

• A control is a standard for comparison in the
  experiment.

• A conclusion is a judgment based on the
  information obtained from the experiment.

• A hypothesis is never proven, only supported or
  discarded.
• A model can be used to make predictions.

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Lets Look at an example The Ozone Layer

• Ultraviolet light damages living organisms.

• Earths atmosphere contains a layer of ozone that
  absorbs ultraviolet light and protects living
  organisms.

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The Ozone Layer (cont.)
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The Ozone Layer (cont.)

• Ozone is a substance in the atmosphere made up of
  oxygen.

• Ozone is formed when oxygen gas (O2) is exposed
  to ultraviolet radiation.

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The Ozone Layer (cont.)

• In the mid-1980s, Scientists detected thin areas
  in the ozone layer over Antarctica.

• What could be causing the ozone hole?

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Chlorofluorocarbons

• Chlorofluorocarbons (CFCs) are used as coolant in
  refrigerators and propellant in aerosol cans.

• CFCs were considered safe because they are
  non-toxic and dont react with other chemicals.

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Chlorofluorocarbons (cont.)

• CFCs were first detected in the atmosphere in the
  1970s, and the concentrations continued to
  increase through the 1990s.

• Was there a connection between ozone thinning and
  increasing CFCs in the atmosphere?

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Section 1.1 Assessment
Which of the following protects living organisms
from harmful ultraviolet light? A. CFCs B. oxygen
gas C. exosphere D. ozone

1. A
2. B
3. C
4. D

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• Two scientists, Mario Molina and Sherwood Rowland
  studied how long CFCs could stay in the Earths
  atmosphere.
• They looked at interactions of chemicals in the
  troposphere. They found CFCs to be stable there
  for long amounts of time, but they also knew that
  CFCs would travel up to the stratosphere.

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• They hypothesized that CFCs break down in the
  stratosphere because of interactions with
  ultra-violet light from the sun. They also
  hypothesized that the chlorine produced in this
  interaction would break down the ozone.

• Molina and Rowlands model showed how CFCs could
  destroy ozone.

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Theory and Scientific Law

• A theory is an explanation that has been
  repeatedly supported by many experiments.

• A theory states a broad principle of nature that
  has been supported over time by repeated testing.
• Theories are successful if they can be used to
  make predictions that are true.
• Theories you may know Modern Atomic Theory, Big
  Bang Theory, Theory of Evolution, Cell Theory,
  Theory of Relativity, Plate Tectonic Theory

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Theory and Scientific Law (cont.)

• A scientific law is a relationship in nature that
  is supported by many experiments, and no
  exceptions to these relationships are found.
• Laws you might be familiar with Newtons laws,
  Law of gravitation, Keplers laws, Boyles law,
  Charles Law, Ideal Gas Law.

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Section 1.3 Assessment
Quantitative data describes observations that are
_____. A. numerical B. conditions C. independent
D. hypotheses

1. A
2. B
3. C
4. D

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Section 1.3 Assessment
Scientific methods are _____ approaches to
solving problems. A. dependent B. independent C. h
ypothetical D. systematic

1. A
2. B
3. C
4. D

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• Example
• George wants to see how the length of daylight
  affects the growth of a sunflower.
• He plants identical seeds in identical pots that
  are filled with the same type of soil and the
  same amount of water.
• He exposes the first flower pot to no sunlight,
  the second to 4 hours of sunlight, and the 3rd to
  8 hours of sunlight.

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A). Which flower pot is the control for this
experiment? B). What is the independent
variable for this experiment? C). What is the
dependent variable for this experiment? D).
What is the quantitative data collected? E).
What type of qualitative data might you collect?