2. Methods

2. Methods
Independent variables
  • Presence of mouthwash

Dependent variables
  • Amount of bacteria observed

Controlled variables
  • The duration of gargling with the mouthwash
  • The amount of mouthwash used when gargling
  • The type of mouthwash used

2.1 Equipment List
  • Agar Plates x 6
  • Cotton Swabs x 10
  • Spreaders x 6
  • Spirit Lamp x 1
  • Pipette x 1
  • 15 ml test tubes x 6
  • ParaFilm x 8
  • Bottle of Sterile Water x 1
  • Mouthwash x 1
  • Lighter x 1

2.2 Diagrams of Experiment Setup
Xuan Yi and Li Kai’s samples ^

2.3 Procedures
  1. Light up the spirit lamp
  2. Place the equipment near the flame to ensure that it does not get contaminated.
  3. Take a cotton swab and swipe the inside of your cheek, trying to get as much of the surface of the swab covered with saliva.
  4. Using the pipette, extract 10 millilitres of sterile water into the test tube.
  5. Dip the swab in the sterile water in the test tube.
  6. Use the pipette and extract 100 microlitres of water and put in on the agar plate.
  7. Use the spreader and spread the sample all over the agar plate.
  8. Rinse your mouth with mouthwash for 30 seconds.
  9. Repeat steps 3 to 6 for the mouthwash.
  10. Cover the agar plates and wrap around the plate with Parafilm.
  11. With the plates agar facing upwards, place the agar plates in the incubator.
  12. Record the number of distinct colonies in the agar plate for next 5 days.

2.4 Risk Assessment and Management  

Cotton swabs may not be sterile, unwanted bacteria may enter our mouth.
Be careful when handling the cotton swab. Do not let the cotton swab touch other surfaces.  Once you take it out from its container, put it directly into our mouth to do the swipe.
We might cut and injure ourselves when transporting the agar plates and drops them.
Be careful when transporting the agar plates and just let 1 person take them.
We might burn ourselves from  the spirit lamp used to prevent contamination from entering our setup.
Be careful when near/dealing the fire. Always follow the instructions from the lab tech/ teacher and extinguish the fire when not in use.
Infection from the bacteria
Take safety precautions and do not come into contact with the bacteria colonies.

2.5 Data Analysis  
1. Gather the results from the experiment.
2. Plot a graph of the day against the number of bacteria colonies seen.
3. The steeper the gradient of the graph, the greater is   the number of bacterial colonies.

4. The samples with the mouthwash has a bigger difference in terms of the number of distinct bacterial colonies,  than the ones with mouthwash.

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