Scientific Method
OHEC
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Observe
Hypothesize
Experiment
Conclude
Observation
A note made by studying something using
sight, sound, touch, smell and taste
• Will all popcorn kernels pop if bagged popcorn is stored in a
cabinet or refrigerator?
• Will warm water or cold water help a plant grow faster?
• Does bar soap clean your hands better than sanitizing
solution?
• Will more ants eat butter or margarine?
• Does salted water boil faster than unsalted water?
Inference
• Inference is just a big word that means a
conclusion or judgement. If you infer that
something has happened, you do not see,
hear, feel, smell, or taste the actual event. But
from what you know, it makes sense to think
that it has happened.
Hypothesis
A scientific guess as to the outcome
of an experiment
• If bagged popcorn is stored in a refrigerator then all the
kernels will pop.
• If a plant is given warm water then it will grow faster than a
plant given cold water.
• If you clean your hands with sanitizing solution then your
hands will not be cleaner than if you used liquid soap.
• If ants are fed butter then they will not eat margarine.
• If salt is added to water then the water will not boil faster.
How to make a hypothesis
If _________________then ________________
independent variable
The variable that is
changed by the
experimenter
dependent variable
The variable that
changes as a result of
the independent
variable
Experiment
• Steps used to conduct an investigation
•One bagged popcorn of the same brand is placed in the refrigerator for 24
hours.
•Two of the same type plant were watered. One plant is given water at 75
degrees Celsius and one plant is given water at 15 degrees Celsius.
•An individual has one hand cleaned with sanitizing solution and the other
hand cleaned with liquid soap. The sanitized hand is allowed to dry while
the other hand is washed for twenty seconds and then rinsed.
•To determine which lipid ants would eat, ants from the same colony were
given ½ tablespoon of margarine and ½ tablespoon of butter.
Experimental vs. Control
Experimental Group
Group subjected
to the
independent
variable
Ex: Cold water for plant or warm
water for plant
Control Group
All variables kept
constant. Used for
comparison during
the experiment
Ex: Room temperature
water for plant
Conculsion
Statement that explains the results of the
experiment
• Popcorn stored in the refrigerator popped better than popcorn
stored in the cabinet; was hypothesis proven or disproven.
• *Plants given warm water grew better than plants given cold
water; was hypothesis proven or disproven
• *Hands cleaned with liquid soap have fewer germs than hands
cleaned with sanitizing solution; was hypothesis proven or
disproven
• *More ants ate the butter than margarine; was hypothesis
proven or disproven
• *The salted water boiled faster than the unsalted water; was
hypothesis proven or disproven
Try it!
In 1928, Sir Alexander Fleming was studying a bacteria growing in culture
dishes. He notices a mold called Penicillium was also growing in some of
the dishes. A clear area existed around the mold because all the bacteria
that had grown in this area had died.
Fleming hypothesized that the mold must be producing a chemical that killed
the bacteria. He decided to isolate this substance and test it to see if it
would kill bacteria. After he grew the mold in a nutrient broth, he
removed the mold and added the broth to a culture of bacteria. The
bacteria died. This is how the antibiotic Penicillin was discovered.
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What was the problem?
What was the hypothesis
What was the conclusion of the experiment.
Lab Tools
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Scalpel
Forceps
Beaker
Hot plate
Microscope
Petri dish
Pipette
Test tube
Slide cover
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Slide
Probe
Graduated cylinder
Goggles
Erlenmeyer flask
Test tube rack
Tongs