Conducting A
Scientific
Investigation
The Scientific Method
Posing a Question
 Ask
a question that can be
answered by gathering evidence
 Which freezes faster- fresh
water or salt?
 The above is a scientific
question because you can gather
information to answer the
question
Developing a Hypothesis
A
hypothesis is a possible
explanation for a set of
observations or answer to a
scientific question
 Based on observations and
previous knowledge and
experiences
Forming a Hypothesis
Must
be in an If… then
statement.
If I add salt to fresh water, then
the water will take longer to
freeze.
Designing an Experiment
 Your
plan should be written out in a
step-by-step procedure
 Your plan should describe the
observations or measurements you will
make
 Two important steps in designing an
experiment: CONTROLLING
VARIABLES and FORMING
OPERATIONAL DEFINITIONS
Controlling Variables



In well designed

experiments, all variable are
the same except one
The factor your change is 
called the manipulated variable
EX: the amount of salt
added to the water is the 
manipulated variable
Keep other factors, amount of
water or starting temperature,
the same
Responding variable is what you
measure or observe to obtain
our results.
Control variable is the factors that
are kept constant which you use
for comparison
Forming Operational Definitions


Have a clear statement
that describes how a
particular variable is to
be measured or how a
term is defined
EX: how would you
determine if water is frozen?


You might decide to
insert a toothpick in each
container at the start of
the experiment
Your definition of
“frozen” would be the
time at which the stick
can no longer move
Interpreting Data






Observations and measurements are called data
You need to analyze the data at the end of the
experiment (look for trends or patterns)
Organize data in a data table or graph
Ask Does the data support my hypothesis?
Does the data point out a flaw in the experiment?
Do I need to collect more data?
Drawing Conclusions




Create a statement that sums up what your have
learned from an experiment
Decide whether the data you collected supports
your hypothesis or not
You need to repeat an experiment to produce
reliability
Conclusions often lead you to pose new
questions and plan new experiments
Making Measurements
Measuring for Accuracy in SI units
Making Observations



You cannot label something as “big” or
“heavy”. These terms are to vague.
You must use instruments to measure how big
or heavy an object is
By measuring, you make observations more
precise and communicate more information
about what you observed
Measuring In SI




International System of
Units: the standard system of
measurement used by
scientists around the world
Based on multiples of 10
Each unit is 10 times larger
than the next smallest unit
Each unit is 1/10 larger than
the next largest unit
Length




Measure length or the
distance between two
things: use the METER
Long distances, are
measured in kilometers
Small lengths are
measured in centimeters
or millimeters
Use metric rulers to
measure length
Liquid volume



Use a unit liter to measure liquid volume
Smaller volumes re measured in milliliters
Use the graduated cylinder to measure liquid
volume
Mass




Measure mass, the amount of matter in an object,
use the gram
One gram is approximately the mass of a paper
clip
Larger masses are measured in kilograms
Scientists use a balance to find the mass of an
object
Temperature



Use the Celsius scale, not Fahrenheit scale!
Temperature is measured in degrees Celsius
Water freezes at 0 degrees Celsius and boils at
100 degrees Celsius