Scientific Method

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Scientific Method
What is the scientific method?
• It is a way in which scientists answer and
solve problems
• The steps to solve a problem or question
Steps of the scientific method
1. State problem or question to be solved or
answered
2. Form a hypothesis
3. Experiment to test hypothesis
4. Collect data from experiment and
observations
5. Form a conclusion
6. Communicate ideas and results
Use observations to form a question
you would like to investigate
• You can use your senses to gather information.
– _______________
observation
Qualitative
• You can use tools to gather information called
measurements
Quantitative
– _______________observation
– Tools make accurate observations.
• Often you are asking a question about the
relationship between things
•
Example: The position of the light source and
the size of the shadow
Hypothesis
• A possible explanation that needs to be tested
• “If…….., then………. will happen.
• Form a hypothesis about the position of the light source
on the object and the length of the object’s shadow.
If the light source gets closer to the object, then the
objects’ shadow will get…
• Hypotheses are NOT facts! Instead it is a possible way to
answer a question.
• Many trials are needed before a hypothesis can be
accepted as true.
Experiment
• When you carry out procedures to test your
hypothesis
• Experiments begin by first examining all the
variables
• Variables are factors that can change in an
experiment
– Can you name a few variables that could change in an
experiment?
• Experiments should be designed so only one
variable is changed!
• There are two types of variables: Independent
variable and dependent variable
Independent Variable
• The variable that is changed in an experiment
– Example: Susan sets up an experiment to test
whether the position of the light impacts the
length of the shadow. In order to test this, she
shines the light on a cereal box from six different
positions. At each position, she measures the
length of shadow the cereal box casts. What
would be the independent variable? (Hint what is
Susan changing?)
The position of the light
Dependent Variable
• The variable that is expected to change
because of the independent variable.
– Example: Think about Susan’s experiment to test
whether the position of the light impacts the
length of the shadow. She shown the light on a
cereal box from six different positions, and at each
position, she measured the length of shadow the
cereal box casts. What is the Dependent variable?
(Hint: what is changing because of Susan’s
independent variable?)
The length of the shadow
Identify the Dependent and
Independent Variables.
• Students conduct an experiment to test if
studying leads to higher tests scores. What
would be the independent variable (the thing
that changes)? What would be the dependent
variable (What is changing because of the
independent variable)?
Independent Variable: Time spent
studying
Dependent Variable: Test score
Identify the Independent and
dependent variable
• A scientist conducts an experiment to test the
theory that a vitamin could extend a person’s
life-expectancy
– What would be the independent variable?
– What would be the dependent variable?
Independent Variable: Taking
Vitamins
Dependent Variable: Life-expectancy
(How long you live)
Identify the independent and
dependent variables.
• Students experiment to see how different
amounts of sunlight impact how much plants
grow.
– What would be the independent variable?
– What would be the dependent variable?
Independent Variable: Amount of sunlight
Dependent Variable: Plant growth
Control Group and Experimental Group
• A control group is a group in a scientific
experiment where no variables are changed.
• It is used to compare results against the a
group where a variable is changed called an
experimental group.
– Example- A student is testing to see if plants will
grow without sunlight.
• Which would be the experimental group and which
would be the control group?
Control
Experimental
What makes a good experiment:
• Control group
• One independent variable
• Testing the hypothesis many times (many
trials)
Collecting and Interpreting Data
• Make observations and record them into a data
table.
• Data tables can be for both quantitative and
qualitative observations.
– Make a data table that would describe some
qualitative observations of different types of rocks
– Make a data table that would describe some
quantitative observations of different types of rocks.
• Graphs are useful way to view quantitative data
because they reveal trends or patterns
Explain the graph
Explain the graph
Explain the graph
Drawing Conclusions
• After scientists interpret their data (with the
help of a graph usually), they draw a
conclusion about their hypothesis.
• Conclusions state whether or not the data
supports the hypothesis
– My hypothesis was correct because….
– My hypothesis was incorrect because…
Should be supported by observations!!!
Communicating
• Sharing ideas and conclusions about your
experiment with others through writing and
speaking
• Scientists share the design of an experiment
as well so others can repeat the experiment to
check the results
• Communicating information about discoveries
often leads to new questions, new
hypotheses, and new investigations.
Model
• Represents an object or system in science.
– Example: Globe of Earth
Theory
• A well tested explanation for many observations
and experimental results.
• Well tested and widely accepted by scientists.
– Example: Atomic theory- all substances are
composed of tiny particles called atoms. This theory
explains many observations: why water freezes or
boils at certain temperature, and why water can
dissolve many other materials
Law
• A statement that describes what scientists
expect to happen every time under a
particular set of conditions
– Example- Law of Gravity “What goes up must
come down.”
• A scientific law describes an observed pattern
in nature without attempting to explain it.

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