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Examining the effect of acidity and alkalinity on bacteria growth inhibitionFeatured science projectScience project video


The objective of this science fair projectis to investigate the effect of acidity and alkalinity on bacterial growth. This will be determined through the use of different concentrations of hydrochloric acid and sodium hydroxide, and measuring the size of the respective inhibition zones in samples of E. coli bacteria.


A higher concentration of acidic and alkaline solutions will result in a larger inhibition zone.

Scientific Terms

Bacteria, microorganism, radioactive waste, acidic, alkali, pathogen



Bacteria are small single-cellmicroorganisms that exist in almost all parts of the world. They can be found in the soil, our body, the earth’s crust, radioactive waste and even the acidic water in hot springs. Bacteria measure only a few micrometers in size, and they are found to have a variety of sizes and shapes such as spirals, rods and spheres.

The majority of the bacteria around us are harmless, and some of them are even necessary for our survival. These beneficial bacteria exist in our body, and can be found in areas such as our stomach and intestine. An example of such bacteria is the species E. coli that aids digestion. . However, there are some types of bacteria that spread diseases and cause people to become ill. These bacteria are known as pathogens. Hence, it is crucial for us to maintain proper personal hygiene and  a clean and safe environment through the use of disinfectants.

Temperature, oxygen availability, pH, salt concentration and nutrient availability are factors that influence the growth and reproduction of most species of bacteria. The optimum temperature for most bacteria to survive and grow ranges from 25 degrees Celsius to 40 degrees Celsius, and the optimum pH levels ranges from 6 to 8. However, some bacteria are able to mutate and evolve to survive under inhospitable environments.

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Complexity level:
Project cost ($):
Time required:
Preparation will require one day, while observation and recording of data will be carried out over a period of three days
Material availability:
Easily found
Safety concerns:

The bacteria should be destroyed with bleach before it is disposed of. Gloves and protective eyewear must be worn when handling the acid and alkali.