scientific method - Southern Local Schools

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Transcript scientific method - Southern Local Schools

Using the Scientific Method
• When you hear or read about
advancements in science, do you wonder
how they were made?
How did the
scientists make their discoveries? Were
they just lucky? Maybe, but chances are
that it was much more than luck. The
scientific method probably had a lot to do
with it!
What is the Scientific Method?
• The scientific method is a series of steps that
scientists use to answer questions and solve
problems. The chart below shows the steps that
are commonly used in the scientific method.
Although the scientific method has several
distinct steps, it is not a rigid procedure whose
steps must be followed in a certain order.
Scientists may use the steps in a different order,
skip steps, or repeat steps. It all depends on
what works best to answer the question.
• Scientists approach problems from a
variety of viewpoints. They conduct their
research using available tools, data, time
and people. Research often leads to new
problems and new hypotheses, which
require further research and testing.
Bell ringer
• How can you prove that the
world is not flat?
Ask a Question
• Asking a question helps you focus your
investigation and identify what you want to
find out. Usually, scientists ask a question
after they’ve made a lot of observations.
• An observation is any use of the senses
to gather information. Measurements are
observations that are made with
• In 1864 and 1865, James Clerk Maxwell
made observations about electricity and
certain observations about magnetism and
showed how the two phenomena are
related. As a result of his investigations,
electromagnetism, one of the most
important scientific advances of the
nineteenth century.
Q: Why is a science lesson like a
worm in a cornfield?
A: They both go in one ear
and out the other.
Just because a hypothesis is untestable does not mean that it is
wrong. It just means that there is
no way to support or not support it.
Scientists must always formulate
hypotheses for which they can
make observations and gather
Form a Hypothesis
• Once you’ve asked your question, your
next step is forming a hypothesis. A
hypothesis is a possible explanation or
answer to a question. You can use what
you already know and any observations
that you have made to form the
hypothesis. A good hypothesis is testable.
If no observations or information can be
gathered or if no experiment can be
designed to test the hypothesis, it is untestable.
Before Scientists Test
a Hypothesis
• They often make a prediction that state
what they think will happen during the
actual test of the hypothesis. Scientists
usually state predictions in an “ If…then…”
1. How do scientists and engineers use the
scientific method?
Scientists use the scientific method to
answer questions and solve problems.
Engineers can use the scientific method to
create new technology.
REVIEW (cont)
2. Give three examples of technology from
your everyday life.
Sample answers:
car engines, CD players, air-conditioning
units, spoons, and doorknobs.
REVIEW (cont)
3. Analyzing Methods. Explain how the accuracy
of your observations might affect how you
develop a hypothesis.
Sample answer: If observations or measurement
are not accurate, they can affect how reasonable
a hypothesis is. As a result, answering the
question may be more difficult and take more time
than if observations and measurements were
accurate from the beginning.
Test the Hypothesis
• After you form a hypothesis, you must
test it to determine whether it is a
reasonable answer to your question.
In other words, testing helps you find
out if your hypothesis is pointing you
in the right direction or if it is way off
the mark. Often a scientists will test a
hypothesis by testing a prediction.
Test the Hypothesis (cont)
• One way to test a hypothesis is to
conduct a controlled experiment. In a
controlled experiment, there is a
control group and an experimental
group. Both groups are the same
except for one factor in the
experimental group, called a variable.
The experiment will then determine
the effect of the variable.
Test the Hypothesis (cont)
• Sometimes a controlled experiment is not
possible. Stars, for example, are too far
away to be used in an experiment. In
such cases, you can test your hypothesis
by making additional observations or by
conducting research. If your investigation
involves creating technology to solve a
problem, you can make or build what you
want to test and see if it does what you
expected it to do.
• Data are any pieces of
information acquired through
experimentation, observation
and research.
Analyze the Results
• After you collect and record your
data, you must analyze them to
determine whether the results of your
Sometimes doing calculations can
help you learn more about your
results. Organizing numerical data
into tables and graphs make
relationships between information
easier to see.
Science Bloopers
• Experiments don’t always turn out as
expected. In 1856, William Henry Perkins
was experimenting to synthesize the antimalarial drug quinine from coal tar. He
didn’t succeed, but he accidentally made
aniline purple (mauve), the first synthetic
dye. Mauve dye was used to color cotton,
wool, and silk. Further experiments led to
the development of many other dyes from
coal tar.
Draw Conclusions
• At the end of an investigation, you must
draw a conclusion. You could conclude
hypothesis, that your results did not
support your hypothesis, or that you need
more information. If you conclude that
your results support your hypothesis, you
can ask further questions. If you conclude
that your results do not support your
hypothesis, you should check your results
or calculations for errors.
Draw Conclusions (cont)
• You may have to modify your
hypothesis or form a new one and
conduct another investigation. If you
find that your results neither support
nor disprove you hypothesis, you may
need to gather more information, test
your hypothesis again, or redesign
the procedure.
Communicate Results
• One of the most important steps in any
investigation is to communicate your
results. You can write a scientific paper,
make a presentation, or create a Web site.
Telling others what you have learned is
how science keeps going. Other scientists
can conduct their own tests, modify your
tests to learn something more specific, or
study a new problem based on your
Breaking the Mold of the
Scientific Method
• Not all scientists use the same scientific
method, nor do they always follow the
same steps in the same order. Why not?
Sometimes you may have a clear idea
about the question you want to answer.
Other times, you may have to revise your
hypothesis and test it again. While you
measurements and record data correctly,
you don’t always have to follow the
scientific method in a certain order.
Building Scientific Knowledge
• Using the scientific method is a way
to find answers to questions and
solutions to problems.
But you
should understand that answers are
very rarely final answers. As our
understanding of science grows, our
understanding of the world around us
New ideas and new
experiments teach us new things.
Building Scientific Knowledge
• Sometimes, however, an idea is
supported again and again by many
experiments and tests. When this
happens, the idea can become a
theory or even a law.
Scientific Theories
• You’ve probably heard a detective on
a TV show say, “I’ve got a theory
about who committed a crime.” Does
the detective have a scientific theory?
Probably not; it might be just a guess.
A scientific theory is more complex
than a simple guess.
Scientific Theories (cont)
• In science, a theory is a unifying
explanation for a broad range of
hypotheses and observations that have
been supported by testing. A theory not
only can explain an observation you’ve
made but also can predict an observation
you might make in the future. Keep in
mind that theories can be changed or
replaced as new observations are made or
as new hypotheses are tested.
Scientific Laws
• What do you think of when you hear
the word law? Traffic laws? Federal
laws? Well, scientific laws are not
like these laws. Scientific laws are
determined by nature, and you can’t
break a scientific law!
Scientific Laws (cont)
• In science, a law is a summary of many
experimental results and observations. A
law tells you how things work. Laws are
not the same as theories because laws
only tell you what happens, not why it
happens. Although a law does not explain
why something happens, the law tells you
that you can expect the same thing to
happen every time.
1. What is the relationship between an
experiment and a hypothesis?
When following the scientific method,
what is the correct procedure for
3. What is a variable?
1. An experiment is a test of a hypothesis to
support or disprove it.
2. There is no correct order as long as steps
are followed so that accurate
measurements are made and data is
3. A factor that can be changed in an
experiment to determine its effect on the
Are the following laws or theories:
1. An object that is dropped falls to the
2. Gravitational forces causes an attraction
between two objects.
3. The universe began with a very powerful
1. (law)
2. (law)
3. (theory)
What is a Model?
• A model is a representation of an object or
system. Models are used in science to describe
or explain certain characteristics of things.
Models can also be used for making predictions
and explaining observations. A model is never
exactly like the real object or system—if it were,
it would no longer be a model. Models are
particularly useful in physical science because
many characteristics of matter and energy can
be either hard to see or difficult to understand.
Models Help You
Visualize Information
• When you’re trying to learn about
something that you can’t see or
observe directly, a model can help
you visualize it, or picture it in your
mind. Familiar objects or ideas can
help you understand something a little
less familiar.
Models Build Scientific
• Models not only can represent
scientific ideas and objects but
also can be tools that you can use
to conduct investigations and
illustrate theories.
Models Can Save
Time and Money
• When creating technology, scientists
often create a model first so that they
can test its characteristics and
improve its design before building the
real thing.
Models Can Save
Time and Money (cont)
• Models allow you to test ideas without
having to spend the time and money
necessary to make the real thing.
1. What is the purpose of a model?
2. Give three examples of models that
you see every day.
3. Interpreting Models. Both a globe
and a flat world map model show
certain features of the Earth. Give
an example of when you would use
a globe and an example of when
you would use a flat map.
1. The purpose of a model is to represent
concepts or characteristics of objects that
are more difficult to see or hard to explain.
2. Acceptable answers include bus maps,
and attendance record, a stuffed animal,
assembly instructions for a bicycle, and
sheet music.
3. Sample answers: A globe would be
better if you wanted to compare the sizes
of different countries; a flat map would be
better if your wanted to carry a world map
in you backpack.
Measurements and Safety in
Physical Science
• Hundreds of years ago, different countries
used different systems of measurement.
In England, the standard for an inch used
to be three grains of barley placed end to
end. Other standardized units of the
modern English system, which is used in
the United States, was based on parts of
the body, such as the foot. Such units
were not very accurate because they were
based on objects that varied in size.
Measurements and Safety in
Physical Science (cont)
• Eventually people recognized that
there was a need for
a single
measurement system that was simple
and accurate. In the late 1700’s, the
French Academy of Sciences began
to develop a global measurement
International System of Units, or SI.
The International System of Units
• Today most scientists in almost all
countries use the International System of
One advantage of using SI
measurements is that it helps scientists
share and compare their observations and
results. Another advantage of SI is that all
units are based on the number 10, which
makes conversions from one unit to
another easier to do. The table in the
appendix of your book contains the
commonly used SI for length, volume,
mass, and temperature.
The International System of Units
• How long is an Olympic-sized
swimming pool?
To describe its
length, a physical scientist would use
meters (m), the basic SI unit of
length. Other SI units of length are
larger or smaller than the meter by
multiples of 10.
The International System of Units
• For example, 1 kilometer (km) equals
1,000 meters. If you divide 1 m into 1,000
parts, each part equals 1 mm. This means
that 1 mm is one-thousandth of a meter.
Although that seems pretty small, some
objects are so tiny that even smaller units
must be used. To describe the length of a
grain of salt, micrometers (um) or
nanometers (nm) are used.
The International System of Units
• Imagine that you need to move some
lenses to a laser laboratory. How
many lenses will fit into a crate? That
depends on the volume of the crate
and the volume of each lens.
Volume is the amount of space that
something occupies.
The International System of Units
(Volume) cont
• Volumes of liquid are expressed in
liters (L). Liters are based on the
meter. A cubic meter (1 m3)is equal
to 1,000 L. So 1,000 L will fit into a
box 1 m on each side. A milliliter
(mL) will fit into a box 1 cm on each
side. So 1 mL = 1 cm3. Graduated
cylinders are used to measure the
volume of liquids.
The International System of Units
(Volume) cont
• Volumes of solid objects are expressed in
cubic meters (m3). Volumes of smaller
objects can be expressed with cubic
centimeters (cm3) or cubic millimeters
(mm3). To find the volume of a crate, or
any other rectangular shape, multiply the
length by the width by the height. To find
the volume of an irregularly shaped object,
measure how much liquid that object
The International System of Units
• How many cars can a bridge support?
That depends on the strength of the bridge
and the mass of the car. Mass is the
amount of matter that something is made
of. The gram (g) is the basic SI unit for
mass and would be used to express the
mass of a car. Grams (one-thousandth of
a kilogram) are used to express the mass
of small objects. A medium-sized apple
has a mass of about 100g. Masses of
very large objects are expressed in Metric
tons. A metric ton equals 1,000 kg.
The International System of Units
• How hot is melted iron?
To answer this
question, a physical scientist would measure the
temperature of the liquid metal. Temperature is
a measure of how hot (or cold) something is.
You are probably used to expressing
temperature with degrees Fahrenheit (0F).
Scientists often use degree Celsius (0C), but the
kelvin (K) is the SI unit for temperature. The
temperature conversion table in the book
compares 0F with 0C, the unit you will most often
see in this book.
Derived Quantities
• Some quantities are formed from
combinations of other measurements.
Such quantities are called derived
quantities. Both area and density are
derived quantities.
Derived Quantities
• How much carpet would cover the floor of your
classroom? It depends on the area of the floor.
Area is a measure of how much surface an
object has. To calculate the area of a
rectangular surface, measure the length and
width, then use this equation:
Area = length x width
The units for area are called square units, such as
m2, cm 2, and km2.
(Using Area to Find Volume)
Area can be used to find the volume of an object
according to the following equation:
Volume = Area x height
What is the volume of a box 5 cm tall whose lid has an
area of 9 cm2?
45 cm3
(Using Area to Find Volume) cont
2. A crate has a volume of 48 m3. The area
of its bottom side is 16 m2. What is the
height of the crate?
3. A cube with a volume of 8,000 cm3 has a
height of 20 cm. What is the area of one
of its sides?
2. 3m
3. 400 cm2
• The original standards for the kilogram
and meter are kept in the International
Bureau of Weights and Measures in
Sevres, France. They are made of 90
percent platinum and 10 percent iridium.
Derived Quantities
• Another derived quantity is density. Density is mass
per unit volume. So an object’s density is the amount of
matter it has in a given space. To find density (D), first
measure mass (m) and volume (V). Then use the
following equation:
Derived Quantities
• For example, suppose you want to know
the density of a gear. Its mass is 75 g and
its volume is 20 cm3. You can calculate
the gear’s density like this:
m 75 g
D   20 cm3  3.75 3
Safety Rules
• Science is exciting and fun, but it can also
be dangerous. So don’t take chances!
Always follow instructions, and don’t take
shortcuts—even when you think there is
little or no danger.
Safety Rules
• Before starting an experiment, get your teacher’s
permission and read the lab procedures
carefully. Pay particular attention to safety
information and caution statements. The chart
on page 27, shows the safety symbols used in
this book. Get to know these symbols and what
they mean by reading the safety information on
page 622. This is important! If you are still
unsure about what a safety symbol means, ask!
1. What does SI stand for ?
2. What is the SI unit of length?
Volume? Mass? Temperature?
3. Name two safety rules of science?
1. International System of Units
2. Meter, cubic meter, gram, kelvin
3. Follow directions, and don’t take
Measuring Skills; Graduated Cylinder
When using a graduated cylinder to measure
volume, use the following procedure:
1. Make sure the cylinder is on a flat, level
2. Move your head so that your eye is level with
the surface of the liquid.
3. Read the mark closest to the liquid level. On
glass graduated cylinders, read the mark
closest to the center of the curve (meniscus) in
the liquids surface.
Measuring Skills; Meter stick or Metric
When using a meter stick or metric ruler to
measure length, keep the following procedures
in mind:
1. Place the ruler firmly against the object to be
2. Align one edge of the object exactly with the
zero end of the ruler.
3. Look at the outer edge of the object to see
which of the marks on the ruler is closest to
that edge. Note: Each small slash between the
centimeters represents a millimeter, which is
one-tenth of a centimeter.
Scientific Notation
Example: Write the number 653,000,000 in
scientific notation.
Step 1: Write the number without the place-holding zeros.
Step 2: Place the decimal point after the first digit.
Step 3: Find the exponent by counting the number of places that you
moved the decimal point.
6.53000000 .
The decimal point was moved eight places to the left. Therefore, the
exponent of 10 is a positive 8. Remember, if the decimal point had to be
moved to the right, the exponent would be negative.
Step 4: Write the number 750,000,000,000 in scientific notation.