Scientific Method
8th Grade
Science
What is the scientific method?
• It is a process that is used to find answers to questions
about the world around us.
Is there only one “scientific method”? No, there are
several versions of the scientific method. Some versions
have more steps, while others may have only a few.
However, they all begin with the identification of a
problem or a
question to be answered based on
observations of the world around
us and
provide an organized method
for conducting and
analyzing
an experiment.

What is a hypothesis?
• It is an educated guess
based on observations
and your knowledge of
the topic.
What is data?
• It is information
gathered during an
experiment.
Identify the Problem
• What do you want to know or explain?
Use observations you have made to write a
question that addresses the problem or topic
you want to investigate
Form a Hypothesis
• What do you think will
happen?
• Predict the answer to your
question or the outcome of
the experiment.
• If . . . . Then . . .
Create an Experiment
• How will you test your hypothesis? Develop a
procedure for a reliable experiment and
address safety rules.
Perform an Experiment
• Follow the steps in your procedure to perform
your experiment. Record data and
observations
Analyze the Data
• Is the data reliable? Does your data and observations from the
experiment support your hypothesis?
•
YES
– Communicate the Results
– Write a conclusion that summarizes the important parts of
your experiment and the results.
Is your data reliable? NO!?!
• Is your data inaccurate or the
experiment flawed?
Perform a
new
experiment
YES- Modify the Experiment
– Rewrite your procedure to address the flaws in the
original experiment.
NO -Communicate the Results
– Write a conclusion that summarizes the important parts
of your experiment and the results.
How to write a Hypothesis
• A hypothesis is an educated guess about how things
work.
• Most of the time a hypothesis is written like this: "If
_____[I do this] _____, then _____[this]_____ will
happen."
• Your hypothesis should be something that you can
actually test, what's called a testable hypothesis. In
other words, you need to be able to measure both
"what you do" and "what will happen."
"If I open the faucet [independent variable], then it will increase the flow of water [dependent
variable].
"Raising the temperature of a cup of water [independent variable] will increase the amount of
sugar that dissolves [dependent variable]."
Identifying Variables
&
Designing Investigations
What is a Variable?
• Simply, something that varies.
• Specifically, variables represent persons or
objects that can be manipulated, controlled,
or merely measured for the sake of research.
• Variation: How much a variable varies. Those
with little variation are called constants.
Independent Variable –
• something that is changed by the
scientist
– What is tested
– What is manipulated
Dependent Variable –
• something that might be affected by the
change in the independent variable
– What is observed
– What is measured
– The data collected during the investigation
Independent Vs. Dependent
• Intentionally
manipulated
• Controlled
• Vary at known rate
• Cause
•
•
•
•
Intentionally left alone
Measured
Vary at unknown rate
Effect
Controlled Variable –
• a variable that is not changed
– Also called constants
– Allow for a “fair test”
For Example:
Students of different ages were
given the same jigsaw puzzle to
put together. They were timed
to see how long it took to finish
the puzzle.
Identify the variables in this
investigation.
What was the independent variable?
• Ages of the students
–Different ages were tested by the
scientist
What was the dependent variable?
• The time it took to put the puzzle
together
–The time was observed and
measured by the scientist
What was a controlled variable?
• Same puzzle
–All of the participants were tested
with the same puzzle.
–It would not have been a fair test if
some had an easy 30 piece puzzle
and some had a harder 500 piece
puzzle.
Last one:
The temperature of water was
measured at different depths of
a pond.
What was the Dependent Variable?
1. Temperature
2. Thermometer
3. Depth of the
water
11
10
0
1
2
3
What was the Control?
14
1. Temperature
2. Thermometer
3. Depth of the
water
6
1
1
2
3
What was the Independent Variable?
100%
1. Temperature
2. Thermometer
3. Depth of the
water
0%
1
0%
2
3
Designing Investigations
The greater the amount of soap in a soap and
water mixture, the bigger a soap bubble can
be blown.
• Rewrite this hypothesis. (If. . Then
. . .)
– Identify the variables
– What exactly will be changed?
How will it be changed?
– What exactly will be measured?
How will it be measured?
The farther a ball drops, the higher it will
bounce.
• Rewrite this hypothesis. (If. . Then . . .)
– Identify the variables
– What exactly will be changed? How will it be changed?
– What exactly will be measured? How will it be measured?
Staple together:
(in this order)
1.
2.
3.
4.
5.
6.
7.
8.
Scientific Method Note sheet
End of Year Calendar
Pre-test
Brain POP quiz
Crossword Puzzle
Hypothesis Writing
Variable Note sheet
SpongeBob Variable worksheet
Writing conclusions
• 3 sentence minimum
• Accept or reject your hypothesis.
• EXPLAIN why you accepted or rejected
your hypothesis using data from the lab.
• Include a summary of the data –
(averages, highest, lowest) to help the
reader understand your results
• List one thing you learned and describe
how it applies to a real-life situation.
• Discuss possible errors that could have
occurred in the collection of the data and
what you could do differently next time.