Hypothesis and Controlling Variables Hypothesis and Controlling Variables LabLab

Part of the Scientific Process of Inquiry

Problem/QuestionProblem/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/QuestionProblem/Question

John wonders if the amount of sugar

used in the recipe will affect the size of the bread loaf?

Caution!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/ResearchObservation/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 HypothesisFormulate a HypothesisAfter 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.”

HypothesisHypothesis

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!The 3 types of variables!

VariableVariable – any of the factors that could change – any of the factors that could change in a Scientific Investigation.in a Scientific Investigation.

3 Types of Variables3 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 Variables3 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 Variables3 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 haveAll experiments should have

a control group.a control group.

Constants/ControllsConstants/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: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: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 PowerFlower PowerSpongeBob 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 PowerFlower 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 LabControlling 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 reporttogether as a group,Using the yellow Butcher paper.

Use your green sheet as a reference.Be sure to have all parts of the ScientificMethod on your labWrite-up.