Lab Safety
EVIDENCE-BASED THINKING
Mr. Grounds
Biology
C210
SCIENTIFIC METHOD
(SCIENTIFIC INQUIRY)
• Make Observations
• Form a Problem Statement (question) based on
observations
• Form a Hypothesis that attempts to explain
observations
• Experiment
– Test the hypothesis with more observations,
measurements, data collection, research . . .
• Develop a Conclusion based on the results of
tests
OBSERVATION
• Visible Fact
• Provable Fact
• Inference:
assumption
PROBLEM STATEMENT
• Careful observations lead to questions
• A Problem Statement is a question that
compares variables
What is the effect of a 1 minute
exercise on my heart rate?
VARIABLES
• A Variable is something that changes
• Independent Variable
– Changes unrelated to other factors
– We change on purpose
– Know the value ahead of time
What is the effect of a 1 minute
exercise on my heart rate?
We know the exercise (activity level) we will use
VARIABLES
• A Variable is something that changes
• Dependent Variable
– Changes depending on other factors
– We are trying to find out
– Do NOT know the value ahead of time
What is the effect of a 1 minute
exercise on my heart rate?
We do not know what our heart rate will be
CONTROL
• A Control is a variable that does NOT change
– Value remains the same (constant)
– Used to compare experimental results
What is the effect of a 1 minute
exercise on my heart rate?
Our heart rate BEFORE the exercise is the control
CONTROLLED VARIABLES
• What would you NOT want to change in this
experiment?
What is the effect of a 1 minute
exercise on my heart rate?
Type of exercise
Intensity of exercise
People who do the exercise
Temperature of Room
HYPOTHESIS
• Testable statement that expresses the
expected answer to the problem
– Has an independent & dependable variable
– What you think the results of the experiment
will show
If we exercise for 1 minute, then our heart
rate will increase because . . .
Hypothesis or Not?
Hypothesis or Not?
• Albert Einstein was the greatest
scientist in history.
Answer: Not. This is an opinion and not
something that could be tested.
Hypothesis or Not?
• Bacteria will grow more quickly in
a warm environment than a cold
environment.
Answer: Yes, this is a hypothesis. This is
testable and has a clearly identifiable
independent variable (temperature) and
dependent variable (bacteria growth).
Hypothesis or Not?
• If a seed is exposed to acids with a
pH less than 4, it will not
germinate.
Answer: Yes, this is a hypothesis. It is
testable and has a clear independent
variable (pH level) and dependent variable
(seed germination).
Hypothesis or Not?
• If a person takes vitamins each day,
they will be healthier.
Answer: No, not a hypothesis. There is no
way to measure “healthier”. If it was more
specific, such as “will have less cholesterol”
and specified which vitamin, then it could be
tested.
Hypothesis or Not?
• If a person lives in the Midwest,
they will be friendlier than other
people.
Answer: No, not a hypothesis. There is no
way to measure “friendlier”.
Hypothesis or Not?
• Growing a plant under a red light
bulb will increase the rate at which
it grows.
Answer: Yes, this is a hypothesis. It could
be tested with an experiment and has a
clear independent variable (light color) and
dependent variable (growth rate).
Hypothesis or Not?
• Raising the temperature of water
will increase the speed in which
Kool-Aid dissolves.
Answer: Yes, this is a hypothesis. It is
testable and has a clear independent
variable (temperature of water) and
dependent variable (rate at which Kool-Aid
dissolves).
Hypothesis or Not?
• If a person plays the lottery, they
will become rich.
Answer: No, this is not a hypothesis. This is
a prediction, not a testable statement.
Hypothesis or Not?
• Children who don’t watch TV are
smarter than children who do
watch TV.
Answer: No, this is not a hypothesis. It is too general,
and therefore, could not be tested. “Smartness” is too
general, as well as “children who watch TV”. If it was
revised to be more specific, i.e.: “Children who watch
more than 10 hours a week of TV will score less on the
state achievement test than children who watch less
than 10 hours a week of TV”, then it could be tested.
Hypothesis or Not?
• If a person does cardio exercise three
or more times per week, they will have
a greater lung capacity than a person
who does cardio exercise less than
three times per week.
Answer: Yes, this is a testable hypothesis. It has a clear
independent variable (amount of cardio exercise/week)
and dependent variable (lung capacity).
Hypothesis or Not?
• German Shepherds are friendlier
than Great Danes.
Answer: No, not a hypothesis. A “friendly”
dog is subjective and not able to be
measured.
Hypothesis or Not?
• A plant that is grown with fertilizer
will grow taller than a plant grown
without fertilizer.
Answer: Yes, this is a testable hypothesis. It
has a clear independent variable (use of
fertilizer) and dependent variable (plant
height).
Hypothesis or Not?
• Store brand batteries are able to run a
battery-operated device, such as a
portable fan, for the same amount of
time as national brand batteries.
Answer: Yes, this is a testable hypothesis. It has
a clear independent variable (brand/type of
battery) and dependent variable (run time in a
portable fan).
Hypothesis or Not?
• If you use Swifter Max solution,
then your floors will
look like new.
Answer: No, not a hypothesis. The
statement is not testable. There is no way to
measure “floor looks like new”.
Hypothesis or Not?
• Hoodia is a natural supplement
that will help people look fabulous.
Answer: No, not a hypothesis. “Looking fabulous”
is not measurable. If this was rewritten, i.e.: “If a
person takes Hoodia twice a day, they will lose 12 pounds per week”, then it could be a hypothesis
because it could be measured and tested.
Hypothesis or Not?
• A plant grown with salt added to
its soil will be shorter than a plant
grown with no salt added to its
soil.
Answer: Yes, this is a testable hypothesis. It has
a clear independent variable (salt or no salt in
soil) and dependent variable (plant height).
Hypothesis—What is it?
• Based on this activity, what is a
hypothesis?
Answer: A TESTABLE statement
with a clear independent and
dependent variable that attempts
to answer the problem statement.
EXPERIMENT
• Plan to test hypothesis & answer problem
statement
• Collects data to determine the value of the
responding (dependent) variable
• Compares the dependent variable to the
independent variable
• Controlled Experiment - only tests 1
dependent variable at a time
EXPERIMENT
• How to take a pulse
• Count beats for 15 seconds
• Multiple by 4
• Take resting pulse rate
• Jog in place for 1 minute
• Take pulse rate
HEART
RATE
AFTER EXERCISE
Y axis
RESTING
HEART
RATE
X axis
CONCLUSION
• Statement that presents findings of the
experiment
• What the data shows
• States if the hypothesis was correct or
incorrect
TESTING PROMOTIONAL CLAIMS
- Observations about Tootsie Pops
- Problem Statements about Tootsie Pops
WHAT IS SCIENCE?
The use of evidence to construct testable explanations &
predictions of natural phenomena as well as the
knowledge generated through the process.
(Phenomena – observable facts or events)
Let’s make up our
own definition!
HYPOTHESIS VS. THEORY
HYPOTHESIS VS. THEORY
• Tentative
(uncertain)
• Explanation
• Testable
• Can be
changed
• Wellestablished
• Highly reliable
Journal Quiz
1. List the steps to the scientific method in the
correct order.
2. What 2 types of variables are included in a
hypothesis?
3. Define science in your own words.
4. What is the most important lab safety rule
and WHY?
5. Design a Venn diagram to distinguish
between scientific hypotheses & scientific
theories.