The Scientific Method
By
Joseph A. Castellano, Ph.D.
TOPS of Santa Clara Valley
(Teaching Opportunities for Partners in Science)
Scientific Method 1
What is Science?

Science is the study of natural processes called
phenomena that we can see, hear or touch.

Science is very broad and investigates living
things such as animals and plants as well as
non-living matter and energy.

In this class, we study Physical Science, which
includes chemistry, physics, astronomy, and
other related topics such as density.
Scientific Method 2
How Scientists Work
 The two key questions that all scientists ask
are WHY and HOW.
 Scientists raise questions about the world
around them and seek answers by making
careful observations. This often leads to an
initial theory or hypothesis.
Scientific Method 3
The Work of Scientists
 Scientists conduct tests called
experiments to discover
why and how a process works
to test the initial hypothesis.
 All experiments, measurements,
and observations are carefully
recorded in a notebook so that
experimental results can be
repeated and verified.
Scientific Method 4
The Scientific Method
 Scientists use experimental results to confirm
the theory or to create a new or modified
theory of why and how the process works.
 The theory is tested by how well it fits with
other theories and predicts new findings.
 Scientist then publish the results in a scientific
journal so other scientists can repeat and
verify the results to test the theory further.
 After many years of testing a theory, it may
become so well accepted that it is recognized as
a Law of Nature.
Scientific Method 5
The Scientific Method
Idea (Hypothesis)
Lab Experiments
Observations
Measurements
Record Results – Formulate Theory
Scientific Method 6
The Scientific Method
Confirm and Test Theory
Publish Findings
Scientists Repeat & Verify Results
Theory Becomes a Law of Nature
New Products Developed
Scientific Method 7
Scientific Measurements
Scientists use the metric system in their experiments
 Concept of Length

The standard unit of length is the
meter, identified as m

Another common unit of length is the
centimeter or cm
1 centimeter (cm) = 1/100 meter (m) = .01 m
or
1 meter (m) = 100 centimeters (cm) = 100 cm
Scientific Method 8
Scientific Measurements
Standard Metric Units of Length
1,000 m
= 1 kilometer (km)
100 cm
=1m
10 millimeters (mm) = 1 cm
1,000 microns (μ)
= 1 mm
ROADS
METRIC RULER
METRIC RULER
MICROSCOPE
Scientific Method 9
Scientific Measurements

Concept of Mass
The metric unit of mass is the kilogram or kg
1 kilogram (kg) = 1/1000 gram (g) = .001 g
or
1 kg = 1,000 g

Concept of Time
The standard unit of time is the second or s
Scientific Method 10
Scientific Measurements
Standard Metric Units of Mass
1,000 g
= 1 kg
PERSON (50 – 60 kg)
1,000 milligrams (mg)
=1g
EGG (45 – 50 g)
1,000 micrograms (μg)
= 1 mg
GRAIN OF SAND (12 μg)
1,000,000 micrograms (μg) = 1 g
Scientific Method 11
Scientific Measurements:

Concept of Temperature
The standard international unit for temperature is degrees
Celsius, designated as o C
Another unit of temperature often used by scientists is
Kelvin, designated as K. K = o C + 273
Degrees Fahrenheit (oF) is mostly used in the United
States by the general public.
The conversion from o F to o C is: o C = 5/9 ( oF – 32).
Scientific Method 12
Scientific Measurements
Accuracy & Precision (Reproducibility)
 Accuracy
How much uncertainty does your measurement have?
Half of the smallest interval marked on the tool
See your metric ruler: if the true value is 10.17
centimeters and the metric ruler has millimeter marks,
then you can be accurate to:
+ .05 cm
or
+ .5 mm
Uncertainty is not about place value, so it is wrong to say
+ .01 mm because you can’t read 1/100 mm on the tool!
Scientific Method 13
Scientific Measurements
Accuracy & Precision (Reproducibility)
 Precision
Do you get the same number over and over?
You measure the mass of a piece of steel three times
and get the following results:
50.2 g
50.4 g
50.3 g
Note the unit g after each number
There are no naked numbers in science!
The average is: (50.2 g + 50.4 g + 50.3 g) / 3 = 50.3 g
so the measurements are precise to + 0.1 g
Scientific Method 14
Scientific Measurements
Accuracy & Precision (Reproducibility)
 There is no such thing as a perfect
measurement so it is important to know both
the accuracy (uncertainty) and precision
(reproducibility) of the measurement.
Scientific Method 15
Scientific Calculations
Balancing of Units
When making calculations always make sure the units balance.
Example: A runner reaches a speed of
10 meters/second, 20 seconds after he starts.
How far does he travel?
D (distance) = V (velocity) x t (time)
D = 10 m x 20 Xs = 200 m
s
X
The answer is 200 meters
Scientific Method 16
The Importance of Science

Science provides the means to improve the way of
life for current and future generations of people.
Scientists:

Develop new instruments and surgical techniques to
identify and cure diseases.

Create new products that improve communications,
transportation, and entertainment.

Ensure the cleanliness and safety of the
environment.

Discover new drugs that improve and extend
health.
Scientific Method 17
The Importance of Science

Science is at work in everyday life.
 An automobile’s operation involves many interrelated
scientific principles including electricity, mechanics,
chemistry, and physics.
 The calculator you use in class employs a combination
of chemistry, physics, and electronic engineering.
 The computers in our classroom use complex
mathematical principles, wireless communication
technology, electronics, mechanics, chemicals, and more.
Understanding science will help in your future
endeavors, regardless of what they might be.
Scientific Method 18