Bacteria on chopping boards
The materials required for the science fair project experiment:
- 8 agar petri dishes
- 8 disinfected swabs
- 1 bottle of disinfected water
- 4 used plastic chopping boards
- 4 used wooden chopping boards
- tap water
- 1 bottle dishwashing soap
- 1 bottle of Dettol soap
- 1 bottle of bleach
- 8 pieces of chicken
- 1 knife
- 1 marker pen
1. For this science fair project, the independent variable is the type of chopping board and the method of cleaning the chopping board. The dependent variable is the size of the bacteria colony in the petri dish. This is determined by measuring the size of the bacteria growth using a ruler. The constants (control variables) are room temperature, the amount of sunlight and the ingredients in the petri dish.
2. The 8 petri dishes that are prepared using the agar are stored in a refrigerator. The petri dishes are brought to room temperature before the start of the science fair project by taking them out of the refrigerator and allowing them to attain room temperature. The petri dishes are labeled W1, W2, W3 and W4 for wooden chopping boards. The remaining petri dishes are labeled P1, P2, P3 and P4 for the plastic chopping boards.
3. The 4 wooden chopping boards and plastic chopping boards are labeled 1, 2, 3 and 4. One piece of chicken is placed on each of the 8 chopping boards and it is cut several times using the knife.
4. The chopping boards are cleaned as follows according to their number :
1 – wash only with water
2 – wash with water and dishwashing soap
3 – wash with water and dettol solution
4 – wash with water and bleach
5. The sterilized swab is first dampened using the sterilized water. The swabs are rubbed over the plastic and wooden chopping boards and then rubbed on the petri dishes according to their numbers. For example, wooden chopping board 1 will the rubbed using the swab and then rolled on petri dish labeled W1.
6. The cover is closed and the 8 petri dishes are kept in a cool dark place for the bacteria to grow.
7. The diameter of the bacteria colony is measured after 5 days and recorded in the table below.
The bacteria should be destroyed before it is disposed of. Pour some bleach into the petri dish to kill all of the bacteria before disposal.