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Bacteria Science Fair Project: How Does Bleach Kill Bacteria?
Bacteria are one celled organisms that are essential for all life’s survival, but they also cause many diseases, including strep throat, cholera, many types of food poisoning, and the Black Plague, to name just a few. Luckily, humans have discovered several disinfectants, or chemicals that kill bacteria. Household bleach, a solution of sodium hypochlorite and water, is one such disinfectant. So how does bleach kill bacteria? It works by damaging bacteria’s proteins (not unlike the way heat makes the protein in egg white solid). Bleach, as you may know, stings human eyes and causes rashes, so it’s important for us to use just enough bleach to kill bacteria. In this bacteria science fair project, you can investigate what concentration of bleach is sufficient for killing bacteria. Please note that this experiment requires a sizeable investment in both equipment and materials. It would be ideal for you to borrow as many of the materials and equipment you can from a high school or college science lab (or a medical lab, if you have access). It would also be ideal to have the hands-on assistance of someone who has done microbiology experiments before.
Also, make sure you have a good understanding of the necessary precautions when working with live bacteria. The species of E. coli suggested is categorized as safe for high school classrooms, but you still need to clean your work area with 10% bleach solution both before and after the experiment. You should clean your hands and wear sterile gloves, and of course no one should eat anything in the area where you are working! The hard thing about doing this kind of experiment is that bacteria are everywhere, so in order to make sure you are doing a controlled investigation, you have to make sure that your initial materials are sterile, or treated and packaged so that they contain no microorganisms. When you are done with your experiment, make sure that all the bacteria on your plates are dead, either by bleach or autoclave. Also be sure to wear protective clothing and eyewear when working with bleach.
Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state's handbook of Science Safety.