*******Please follow the steps below today whether you started your experiment on Wednesday, Thursday or will start it tonight.
1. Place a drop (no more) of white vinegar in the middle of one of your petri dishes.
2. Using another cleaner, place a drop of cleaner in your second petri dish. You may use a cotton swab if you need to. It may help you get a small circle of cleaner in your petri dish.
3. Using your third cleaner, place a drop of cleaner in your third petri dish.
*** You may use cotton swabs if you need to. It may help you get a small circle of the cleaners in your petri dishes.
4. Cover each Petri dish with the top half and use a piece of paper or tape to label the dish with the name of the item you tested. Place the sealed Petri dish inside a zipper-lock bag and seal it closed. For safety reasons, do not ever open the zipper-lock bag – you can view the growing bacteria through the clear plastic bag.
5. Place the plates in a warm dark place to grow – not too warm, but anything up to about 98 degrees F (37 degrees C) should be fine. In a short time, you’ll be greeted by an amazing variety of bacteria, molds, and fungi. You should continue to see more and larger colonies for the next few days, but you should not see any growth where the disinfectants (cleaners) are. You might even see a “halo” around each spot where you placed the cleaners. This halo is called the “kill zone” – measure and compare the size of the kill zone to determine the effectiveness of different antibacterial agents. Remember… Do not open the plates once things begin to grow.
6. Remember not to open the zipper-lock bags during or after the experiment. When you’re finished analyzing your growing bacteria, dispose of the entire bag in the trash. Do not bring the petri dishes to school.
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