Thanks for the additional explanation. I would never have guessed that English is your second language from your correspondence. Your English is excellent!
Your project is complete, and you really don't need to do another experiment. Your presentation is tomorrow, and the project is due on Tuesday, so you should concentrate on the oral and written presentations rather than do more experiments. Communicating results is as important as doing the experiments.
1. You are applying antiseptic directly to the agar surface, and then looking for the growth of bacteria on the agar surface. This experiment tests for the ability of colonies that are forming on the agar to survive, but does not give you a quantitative result. To measure the resistance of bacteria, you would need to start with individual microorganisms, expose them to the antiseptic, and then grow them on the agar to count them.
2. Two experiments are not enough to demonstrate the development of resistance, and your experimental design will not test for this. You would need to select colonies that survive the antiseptic, culture them, and then design experiments that would demonstrate increasing antiseptic resistance. This is really a whole science fair project that would be good to save until next year. If you do go ahead and set up another experiment, do it in duplicate so you can get an idea of the reproducibility of your technique. Setting up experiments twice, rather than one time, is better scientifically.
3. Scientists like to measure things, so you should try to measure the volume of antiseptic you use. If you do the experiment again, you need to try to add the same amount of bacteria to each plate. I'm not sure from your first experiment where the bacteria came from.
Here are some comments on your write-up.
1. Your approach to the analysis of your results is correct. If 52 colonies are present on the untreated plate, and 12 on the treated, then you observed a 77% reduction in colonies. You should not use decimal points because your results are not significant to .01%.
2. You changed from Clorox, which contains sodium hypochlorite, to Germ-X, which contains ethyl alcohol (ethanol) and other ingredients:
Active Ingredients: Ethyl Alcohol (62%) (Antiseptic)
Inactive Ingredients: Carbomer, Fragrance, Glycerin, Isopropyl Alcohol, Isopropyl Myristate, Propylene Glycol, Tocopheryl Acetate, Water
Did you include information about how ethanol kills bacteria? Here is a website that contains information about various bactericides:http://www.umsl.edu/~microbes/pdf/disinfectants.pdf
This website explains how ethanol kills bacteria:http://www.parish-supply.com/what_reall ... _germs.htm
Do you have any other questions about your write-up? Have you included every section on the outline your teacher gave you?
Don't worry about wasting my time at all. Science buddies is a resource that you should use whenever you need help with a science fair project, and I hope my comments have helped you. Next year, write us a little earlier, and we'll give you suggestions that will help you design your experiments.
Good luck on you presentation tomorrow!