Hypothesis and Controlling Variables
Lab
Part of the Scientific Process of Inquiry
Problem/Question
John watches his
grandmother bake
bread. He ask his
grandmother what
makes the bread rise.
She explains that yeast
releases a gas as it
feeds on sugar.
Problem/Question
John wonders if the
amount of sugar
used in the recipe
will affect the size
of the bread loaf?
Caution!
Be careful how you use effect and affect.
Effect is usually a noun.
Affect is usually a verb.
“ The effect of sugar amounts on the
rising of bread.”
“How does sugar affect the rising of
bread?”
Observation/Research
John researches the
areas of baking and
fermentation and tries
to come up with a way
to test his question.
He keeps all of his
information on this
topic in a journal.
Formulate a Hypothesis
After talking with his
teacher and conducting
further research, he
comes up with a
hypothesis.
“If more sugar is added,
then the bread will rise
higher because sugar
makes bread rise.”
Hypothesis
The hypothesis is an educated guess
about the relationship between the
independent and dependent
variables.
Let’s learn about the 3 types of
variables!
The 3 types of variables!
Variable – any of the factors that could change
in a Scientific Investigation.
3 Types of Variables
• Independent Variable – something that is changed
by the scientist
– What is tested
– Found after the word “if” in the hypothesis
• The independent variable in John’s experiment is
sugar.
• John is going to use different amounts of sugar
(25g., 50g., 100g., 250g., 500g. )in his experiment
to see if the bread will rise higher with more sugar.
3 Types of Variables
• Dependent Variable: something that might be
affected by the change in the independent variable
– What is observed
– What is measured to gather results
– Is found after the word “then” in the hypothesis
– The data collected during the investigation (graph,
chart, etc.)
• In John’s experiment, the dependent variable would
be the size of the loaf of bread.
3 Types of Variables
• Controlled Variable: a variable that is not
changed
– Also called constants
– Allows for a “fair test”
• Control group: exposed to the same
conditions as the experimental group,
except for the variable being tested.
• Serves as the standard of comparison.
• The control group may be a “no treatment"
or an “experimenter selected” group.
All experiments should have
a control group.
Constants/Controlls
• John keeps all other factors the same,
except for the amount of sugar in each
recipe, so that any observed changes in
the bread can be attributed to the
variation in the amount of sugar.
• The constants would include: all the other
ingredients to the bread recipe, oven
used, rise time, brand of ingredients,
cooking time, type of pan used, air
temperature and humidity where the
bread was rising, oven temperature, age
of the yeast.
Identify the variables:
• Hypothesis: If we add more air, then ball
will bounce higher because the ball will be
fuller.
– Independent variable:
• the amount of air in the ball
– Dependent variable:
• How high the ball bounces
– Controlled variables:
• type of ball, drop the ball from the same height, drop
the ball on the same surface
Identify the variables:
• Hypothesis: If a plant gets sunlight then
it will grow because sunlight helps
plants grow.
• Independent variable:
– sunlight
• Dependent variable:
– Growth of plants
• Controlled variable:
– Type of plant, pot, dirt, water, location,
fertilizer
Flower Power
SpongeBob loves to garden and want to grow lots
of pink flowers for his pal Sandy. He bought a
special fertilizer to see if it will help plants produce
more flowers. He plants two plants of the same
size in separate containers with the same amount
of potting soil. He places one plant in a sunny
window and waters it every day with fertilized
water. He places the other plant on a shelf in a
closet and waters it with plain water every other
day.
What did SpongeBob do wrong
with this experiment?
Flower Power
• Too many things are different!
• In order to test the fertilizer correctly,
both plants should have been placed in
the sunny window and watered every
day.
• The only difference should be that one
plant is watered with plain water and
one plant is watered with the fertilizer
water.
Controlling Variables Lab
• Follow the directions on the lab sheet.
• As you work, identify the variables in this lab.
• Complete all questions on both sides of the lab sheet to hand
in.
• Write a lab report
together as a group,
Using the yellow
Butcher paper.
Use your green
sheet as a reference.
Be sure to have all
parts of the Scientific
Method on your lab
Write-up.