Variables:
You should learn:
*About
the
different types of
variables
*How to identify
them when doing
your work
Scientific Experiments Follow Rules.
• A scientist changes
one factor and
observes or
measures what
happens.
3
Variables
• The factor that is changed is known
as the independent variable.
• The independent variable is what you are testing!!
4
• To insure a fair test, a good experiment has
only one independent variable.
• As the scientist changes the independent
variable, he or she observes what happens.
The independent variable is
the thing that someone
actively changes; while the
dependent variable is the
thing that changes as a
result.
In Other Words
• The scientist focuses his or her
observations on the dependent
variable to see how it responds
to the change made to the
independent variable
No notes!!!
The Control
• The scientist makes a special
effort to keep other factors
constant so that they will not
affect the outcome.
• Those factors are called
controls.
8
What is the Purpose of a
Control?
• Controls are NOT being tested
• Controls are used for
COMPARISON
9
Example of Controls & Variable
• For example, suppose you want to
figure out the fastest route to walk
home from school. You will try
several different routes and time
how long it takes you to get home by
each one.
10
Example of Controls & Variable
• For example, suppose you want to
figure out the fastest route to walk
home from school. You will try
several different routes and time
how long it takes you to get home by
each one.
11
What is the Independent
Variable in this scenario?
• What is the independent variable?
• Different routes
• What is the dependent variable?
• Different times
12
List Your Controls
•
•
•
•
•
Same
Same
Same
Same
Same
walker
time of day
shoes
weather
pace
13
The Bikini Bottom gang loves
science class and wants to do a
little research. Read the
description for each experiment
and use your knowledge of the
scientific method to answer the
following questions.
Flower Power
SpongeBob loves to garden and wants to grow lots of pink
flowers for his pal Sandy. He bought a special Flower
Power fertilizer to see if it will help plants produce more
flowers. He plants 2 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 day.
What did Sponge Bob do wrong in this experiment? Explain.
• The following scenarios can be used for
practice to identify variables and controls.
SpongeBob and Patrick love to go jelly fishing. They wondered if a new brand of
jellyfish bait would help them catch more jellyfish. To test their idea, they bought
a big container of bait for their next 3 trips to their top-secret fishing spot.
SpongeBob fished without any bait, while Patrick used the new bait. Both of them
kept track of how many jellyfish they caught in 30 minutes, which is shown in the
chart.
1. What is the independent variable? Jelly Fish Bait
2.What is the dependent variable?
Sponge Bob
Patrick
25
24
18
28
26
19
Number of Jelly fish caught
3.Based on the data, how would you rate the
new bait?
The bait appears to have helped a small amount, but
shouldn’t be rated as a great deal. Overall Patrick caught 2
more jellyfish
Read the information below and then answer the questions
•
.
SpongeBob noticed that his favorite pants were not as clean as they used to be. His friend Sandy told
him that he should try using Clean-O detergent, a new brand of laundry soap she found at Sail-Mart.
SpongeBob made sure to wash one pair of pants in plain water and another pair in water with the
Clean-O detergent. After washing both pairs of pants a total of three times, the pants washed in the
Clean-O detergent did not appear to be any cleaner than the pants washed in plain water.
1. What was the problem Sponge Bob wanted to investigate?
2..What is the independent variable?
3.What is the dependent variable
4. What are the controls?
1. What was the problem SpongeBob
wanted to investigate?
2. What is the independent variable?
3. What is the dependent variable?
4. What are the controls
Super Bubbles
Patrick and SpongeBob love to blow bubbles! Patrick
found some Super Bubble Soap at Sail-Mart. The ads claim
that Super Bubble Soap will produce bubbles that are twice
as big as bubbles made with regular bubble soap. Patrick
and SpongeBob made up two samples of bubble solution.
One sample was made with 5 oz. of Super Bubble Soap and
5 oz. of water,
while the other was made with the same amount of water
and 5 oz. of regular bubble soap. Patrick and SpongeBob
used their favorite bubble wands to blow 10 different
bubbles and did their best to measure the diameter of
each one. The results are shown in the chart
1. What did the Super Bubble ads claim?
2. What is the independent variable?
3. What is the dependent variable?
4. Look at the results in the chart.
a. Calculate the average diameter for each bubble
solution.
Super Bubble = ______ cm Regular Soap = ________ cm
b. What should their conclusion be?
5. Are the results reliable? Why or why not?