4. Discussion

4. Discussion

4.1 Key findings & Analysis of results

From experiment B, our group found out that the effectiveness of the lower concentrations was not as effective as the undiluted one. However, they were still more effective than most
of the other killing agents. The concentrations’ effectiveness also dropped drastically as time passed.  The anomaly for this experiment was that the kill zone of the undiluted clorox
shrunk dramatically after each day. As shown on the second table in Section 3 results, the killzone grew smaller by around an average of 2cm^2 from the first day to the second day
whereas the others only at most drop by 1 cm^2. 

4.2 Explanation of key findings  

For experiment A, the killing agents Jif and Mama Lemon were not effective in killing the germs in our environment. A possible reason for Jif, Mama Lemon and the
Mama lemon is not effective because they are not suited to kill the germs in our school environment but rather more used for removing tough dirt rather than killing bacteria. As for
Clorox, its effectiveness might have gone down as the chlorine in it evaporates and escapes overtime. For Mr Muscle and Dettol, even though the greasy end of the soap molecule
sticks out from the surface of the bubble which results in the soap film being protected from evaporation where it prolongs the life of the soap, the chemicals will still evaporate away,
just not as fast as chlorine. Bleach is a strong and effective disinfectant – its active ingredient sodium hypochlorite is effective in killing bacteria, fungi and viruses, including influenza
virus – but it is easily inactivated by organic material. Diluted household bleach disinfects within 10–60 minutes contact time (World Health Organization, 2014) and Despite the
widespread household use of cleaning and personal hygiene products containing antibacterial ingredients, their effects on the incidence of infectious disease symptoms have not
been studied. (Elaine L. Larson, PhD, Susan X. Lin, DrPH, Cabilia Gomez-Pichardo, MD, and Phyllis Della-Latta, PhD, 2004)

For experiment B, the chlorine in the concentrations of Clorox evaporates quickly as chlorine evaporates faster when in contact with air. Since the air was present in the petri dish,
this explains why the kill zone for all Clorox concentrations shrunk more quickly than the rest of the soaps, especially the undiluted one as it has the most chlorine. Also, a possible
reason why undiluted Clorox is more effective than the other concentrations is that it has significantly more chlorine than the rest. The different concentrations also have about the
same amount of chlorine. Hence it was still more effective than the other concentrations despite more chlorine being evaporated from the rest. Understanding the concentration of
your bleach solution is important for achieving effective disinfection. Bleach (usually 5.25% or 6.00%–6.15% sodium hypochlorite depending upon manufacturer) is usually diluted
in water at 1:10 or 1:100. Approximate dilutions are 1-1/2 cups of bleach in a gallon of water for a 1:10 dilution (~6,000 ppm) or 1/4 cup of bleach in a gallon of water for a 1:100
dilution (~600 ppm)(3M, 2011)

4.3 Evaluation of Hypothesis
For the first experiment, the results match our hypothesis is correct. Our hypothesis is the more acidic the chemical is, the less likely bacteria will survive. The more acidic
chemicals like Clorox and Mr Muscle killed more bacteria. 

For the second experiment, the results match our hypothesis. Our hypothesis is the less concentrated Clorox is equally as effective as the fully concentrated Clorox in killing
bacteria. Even though the undiluted Clorox is shown to be a lot more useful than the lower concentrations, the 4:1 and 3:2 concentrations of Clorox generally have a larger kill
zone than the other killing agents, proving that lower concentrations of Clorox are also effective in killing bacteria. Hence, this shows that our results suit our second experiment. 

4.4 Limitations and Areas for improvement 

In every experiment, there is bound to have limitations and areas for improvement. Sometimes when members in the group use tweezers to place the paper disk into the respective solutions, our excitement causes our hands to dip the paper disk too fast, accidentally soaked it much wetter than the others. This might cause our results to be slightly inaccurate. Hence, in the future, we will slowly and carefully dip our paper disk into the respective solutions.  

Also, sometimes when members of the group soak too much, the paper disk will become too wet, causing it to slip out of place on the petri dish, causing inaccuracy to our results again. Hence, in the foreseeable future, we aim to make the paper disk not so wet by spreading the excessive solutions of the paper disk on the sides of the bottle. This would allow the paper disk to be dampened before placing it on the paper disk in order for it to stick to the petri dish more and have a lower chance to be slipped away. 

Many times all of the members in the group tend to put different amounts of bacteria on the petri dish as sometimes all of us forgot that bacteria has been applied to it already. This caused inaccuracy in the experimentation results. So, all members of the group should put the Petri dishes that have already been applied to one side and the rest on the other side. There should be a separation in the middle to prevent accidentally sweeping some across to the other of the table. This will allow us to apply equal amounts of bacteria on every respective petri dish.