Lecture 1
Scientific Method
Ozgur Unal
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Lesson Objectives
1) Describe the steps in a scientific method.
2) Distinguish qualitative and quantitative
data.
3) Define hypothesis, theory and law.
4) Determine dependent variables,
independent variables and control in an
experiment.
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Science
is a process that uses observation and
investigation to gain knowledge about the events
in nature.
Observation: Act of gathering information
Investigation: Includes observing,
experimenting, modelling
Scientific method is a systematic approach used in
scientific study.
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Hypothesis:
An educated guess
Experiment: A way to test hypothesis
•Collect
data
•Analyze data
•Draw conclusions
Experiments include variables:
•Dependent variables
•Independent variables
•Constants
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In
experiments, two types of data can be
collected:
•Qualitative data:
Anything that relates to five senses
•Quantitative data: Numerical information
Observe the liquid shown to you. Record your
qualitative and quantitative data
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Question:
How does the type of music cows listen
affect the amount of milk they produce?
Hypothesis?
Design
an experiment to test your hypothesis.
Identify independent & dependent variables and
constants
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A
theory is an explanation of a natural
phenomenon based on many observations and
investigations over time. (Electromagnetic Theory)
A
scientific law is a concise but general statement
about how nature behaves. (e.g F=m*a)
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Lecture 2
The Ozone Layer and Chemistry
Ozgur Unal
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UV
light in electromagnetic spectrum is more
energetic than visible light.
Dangerous for living things.
What
protects the living things from UV light coming
from the Sun?
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Ozone
layer in the atmosphere protects life from UV
light.
http://svs.gsfc.nasa.gov/vis/a000000/a000800/a000834/
index.html
Ozone,
which is made up of oxygen, is a substance in
the atmosphere that absorbs UV light.
A substance, which is also known as a chemical, is
matter that has a definite and uniform composition,
like pure water.
Ozone layer is located in the stratosphere.
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How
does ozone enter atmosphere?
UV light
3
O2 -------------------------------------------------------- > 2 O3
Ozone
was first identified and measured in the late
1800s.
It makes a convenient marker to follow the flow of air
in the stratosphere.
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British
scientist G.M.B. Dobson began measuring the
amount of ozone in the atmosphere in the late 1920s.
Normal levels of the amount: 300 Dobson units (DU)
At the beginning of the 1980s, a research group found
levels of ozone as low as 160 DU
The
reports showed a decrease in the thickness of the
ozone layer.
What could be the reason for the thinning of the
layer?
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Large
scale production of refrigerators and airconditioning units that use CFCs (chlorofluorocarbon)
as coolers were being produced by 1930s.
CFCs were also used in spray cans.
CFC is a substance that contains Chlorine, Fluorine
and Carbon.
It does NOT occur naturally.
It does not readily react with other substances. This is
why scientists thought it was safe for the environment.
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Scientists
first began to detect the presence of CFCs in
the atmosphere in the 1970s.
They
measured the amount of CFCs and saw a year
after year increase in the amounts.
By
1990, the CFC concentration has reached an all
time high.
Increasing level of CFCs and the thinning in the
ozone layer. Could they be connected?
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Scientists
determined that CFCs and also two other
substances (carbon tetrachloride and methyl
chloroform) react with ozone and harm the ozone
layer.
Ozone layer is an international concern.
In 1987, world leaders met in Montreal and signed
the Montreal Protocol.
The Protocol phased out the use of these substances
and put some restrictions on how they should be used
in the future.
The CFCs concentration declined after the protocol.
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