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Science and the
scientific methodMr. Banks
7th and 8TH grade science
What is science?
Science is the study of the
structure and behavior of the
physical and natural universe, to
find explanations to why and
how things occur.
What is science?
Scientists collect and
organize information. They
look for patterns and
connections within the
information they gather.
Scientists then propose
explanations that can be
tested by examining
evidence.
Observations and data
Science begins with an observation about the
universe.
Plants grow differently based on how much they
are watered.
Different metals conduct electricity differently.
Observations and data
An observation is the
process of gathering
information, or data,
about something.
Data is the information
gathered from making
observations.
Data
There are two types of data.
Quantitative data are observations
that can be measured or counted.
Ex. There are a certain number of
males and females in this class.
Qualitative data are observations
that are descriptions or cannot be
counted.
Ex. The softness of a cat’s fur.
Hypothesis
A Hypothesis is a testable scientific
explanation for a set of observations.
The explanation must be testable to
be a hypothesis.
The scientific method
Scientists follow a set of guidelines when
investigating natural occurrences.
The scientific method is a procedure for
asking and answering scientific questions
by making observations and doing
experiments.
It is a cycle where questions are asked,
information is gathered, and new
questions are asked.
The scientific method
1. Make an observation
2. Research
3. Create a hypothesis
4. Design an experiment
5. Gather and analyze data
6. Draw conclusions
7. Share results
8. Modify and repeat?
1. Make an observation
Identify a question or problem you or others
have observed.
How much water can a plant’s roots absorb?
Why does a plant stem bend toward the light?
What effect does temperature have on heart
rate?
2. Research
Find out if others have asked this question
and find out what they found.
Look online, in books, and in scientific
journals.
3. Create a hypothesis
After considering the
information out there
now, create a possible
explanation to the
question.
This is just a prediction
and must be tested.
4. Design an experiment
A hypothesis must be tested.
An experiment is a procedure designed to
create a situation in which data can be
gathered to support or refute a hypothesis.
We’ll talk about how to design an
experiment later.
5. Gather and analyze data
Data created by an experiment
must be recorded and analyzed to
determine if they are reliable and
what they mean.
6. Draw conclusions
What information did we
learn?
Has the hypothesis been
supported or did the
experiment indicate the
hypothesis might be
wrong?
Do we need to conduct a
new experiment?
7. Share the information
Tell others, usually in written form, so when
they do research about their own
observations, they will have your information
to help them.
Science builds over time.
If I have seen further it is by standing on the shoulders of Giants.
-Sir Isaac Newton
8. Modify and repeat?
Do I need to repeat my experiment to learn
more?
Do I need to do a different experiment to
gather more evidence?
Usually, yes. Science is basically never finished.
Grog the ancient farmer
1. Make an observation
2. Research
3. Create a hypothesis
4. Design an experiment
5. Gather and analyze
data
6. Draw conclusions
7. Share results
8. Modify and repeat?
Designing an experiment
Scientific ideas must be tested by
experimentation and gathering data.
Scientific experiments must be designed in a
deliberate way.
Enough data must be gathered to learn
something, but having too much in an
experiment can make the results confusing.
Variables
Variables are factors of an experiment that can change.
Ex. Temperature, amount of light, time, concentration of chemicals, or species of animal.
Some variables the scientist will changes, but others change on their own.
In a well designed experiment, the scientist only changes one variable at a time.
If multiple variables are changed at once, you might have trouble figuring out which one is effecting your results.
Variables
There are two types of variables.
The independent variable is the variable that
is directly changed by the scientist.
Remember, scientists usually only change ONE
variable at a time.
Variables
There are two types of variables.
The dependent variable(s) are the changes
observed during the experiment.
This is the data collected during the experiment.
Dependent variables change as a result of
changing the independent variable.
Grog the ancient farmer
What would be the
independent and
dependent variables
in Grog’s experiment?
Today you will need your
interactive notebook, a glue stick,
and a pair of scissors. Get these
after you do your journal.
Variables
Within an experiment there are two groups; the
control and the experimental.
The two groups are identical except for one
factor.
The independent variable.
The experimental group is the group in which
the independent variable has been changed.
Variables
The control is the “normal group” in an
experiment where everything, including the
variable being tested, is kept at what is
considered “normal”.
This group’s purpose is to serve as a comparison for
the experimental group.
Example
In order to test the effectiveness of a new vaccine, 50
volunteers are selected and divided into two groups.
One group will be the control group and the other will
be the experimental group. Both groups are given a pill
to take that is identical in size, shape, color and texture.
Describe the experimental group.
Describe the control group.
What variables are kept constant?
What variable is being changed?
This group will receive the vaccine.
Even though they are given identical
looking pills, they will not actually receive
the vaccine.
The size, shape, color, and texture of
the pill.
Whether or not the pill contains the
vaccine.
Practice Problem:
You want to determine the effects of a certain fertilizer on the growth of tomatoes grown in a greenhouse. Materials that are available to you include: a greenhouse, 100 orchid plants, water, fertilizer, and soil. You want to know if the orchids will grow best with a weak concentration of fertilizer, a medium concentration of fertilizer, or a high concentration of fertilizer. How will you design an experiment to test different concentrations of this fertilizer?
State your hypothesis:
Possible answer:
I predict that the
orchids will grow best
with a medium
concentration of
fertilizer.
How will you set up an experiment?
The 100 plants will be divided into 4
groups as follows:
The plants will be
watered daily.
Over a period of a
month, the plants
will be measured
to see which ones
grew the tallest.
Group 1: 25 plants will receive plain
water.
Group 2: 25 plants will receive a weak
concentration of fertilizer.
Group 3: 25 plants will receive a
medium concentration of fertilizer.
Group 4: 25 plants will receive a high
concentration of fertilizer.
Control Group Experimental Group
What is the control
group in this
experiment?
The control group
consists of the 25 plants
that are receiving plain
water. What is the experimental
group in this experiment?
The experimental group
consists of the 75 plants
that are receiving various
concentrations of
fertilizer.
In a good experiment, all variables must be kept
constant except the one variable that is being
changed.
What variables must be kept
constant in this experiment?
All plants must receive the same amount of
water/fertilizer each day.
All plants are grown in pots of equal size.
All plants are grown at the same temperature.
All plants receive the same amount of sunlight.
All plants are the same species.
What variable is being changed in this experiment?
The variable being changed is the amount of
fertilizer received by each group of plants.
Group 1 (Control Group): Grew to an average height of 15 cm.
Group 2 (Weak conc.): Grew to an average height of 35 cm.
Group 3 (Medium conc.): Grew to an average height of 28 cm.
Group 4 (High conc.): Grew to an average height of 10 cm.
Is your hypothesis supported or disproved
by these results?
We hypothesized that the corn would grow
best with a medium concentration of
fertilizer.
The results do not support our hypothesis.
After one month of measuring the corn,
the following data is obtained:
Titling an experiment
Scientific studies have simple, straight forward titles that often follow this format.
The effect(s) of (the independent variable) on(the dependent variable.
For example:
The effect of different amounts of fertilizer on the height of corn plants.
The title may be boring, but it is very informative.
Writing a hypothesis
Hypotheses also generally
follow a format in order to
convey a lot of information.
If (the independent variable)
is (increased, decreased,
changed), then (the
dependent variable) will
(increase, decrease, change).
For example
If the amount of fertilizer is
increased, then the height of
the corn will increase.
Question
Why is it important to have a large
sample size in any experiment?
If the sample size is too small, an inaccurate conclusion
may be reached.
Ex. An accident occurs and the one control plant dies. Now
we don’t have anything to compare our experimental plants
to.
Vs.
Why is it important to repeat the
experiment many times?
Experiments should be repeated to see if the
same results are obtained each time. This
makes the results more believable.
Question
+ +
What is the importance of the control?
The control shows what
will happen under normal
circumstances. Without
the control, there is
nothing to compare your
results to and no way to
know how your
independent variable
effected your experiment.
Question
On page 7 of your interactive notebook, I
want you to come up with and create a
picture that demonstrates the relationship
between a pair of independent and dependent
variables. Similar to the one below.