Transcript The Effect of Bleach on Bacteria

Bailey McCue
Grade 9
Academy of Notre Dame de Namur
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The purpose of this experiment was to find
the weakest solution of bleach in water that
would effectively kill E. Coli and B. Cereus
bacteria.
Escherichia Coli
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Gram negative
Rod shaped facultative
anaerobe
Found in small
intestines.
Bacillus Cereus
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Gram positive
10% bleach in water solution is sufficient to kill most
bacteria.
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If different bleach solutions are tested on
bacteria, then the weakest solution of bleach
in water that will effectively kill bacteria will
be found.
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Escherichia Coli bacteria
Bacillus Cereus bacteria
Bleach
Water
16 agar plates
48 sterile discs
Inoculating Loop
Forceps
Ruler
Marker
Tape
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1. Prepare solutions of 0.5%, 1%, 3%, 5%, 8%, 10%, and 15%
bleach in water.
2. Label each of the agar plates with the solution and the
bacteria to be tested.
3. Inoculate 8 plates with E. Coli and 8 plates B. Cereus
using the inoculating loop.
4. Hold a single sterile disc with the forceps, dip it into a
bleach solution, then place it in corresponding agar plate.
Do this three times for each bleach solution.
5. Place all plates in an incubator and allow to incubate
over night.
6. Examine all plates and using a ruler with mm, measure
the zones of inhibition.
7. Safely dispose of all plates.
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The independent variable is the strength of
the bleach solution used. (bacteria?)
The dependent variable is the amount of
bacteria killed.
The constants are the amount of bacteria,
amount of solution applied to each sample,
temperature, time, type of bacteria and type
of bleach.
The controls were the agar plates with the
sterile discs soaked in water
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The results of this experiment supported my
hypothesis that the if different bleach
solutions are tested on bacteria, then the
weakest solution of bleach in water that will
effectively kill bacteria will be found.
The weakest solution of bleach in water to
effectively kill bacteria was the 3% solution.
Anything below this solution was ineffective.
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Thank you for listening to my presentation.
Are there any question?