Bacteria growth internal

Y11 Science

Hornby High School

Internal Assessment Resource

Disinfectants

Supports internal assessment for:

Subject Reference:  Science 1.10 v3

Investigate life processes and environmental factors that affect them

Credits: 4

Name:                                                                                                            Grade

Planning Sheet           Student name:

1.    Purpose of investigation (this may be an aim, testable question, prediction or hypothesis)  In this investigation, we are going to look at how Dettol effects the growth of bacteria.
2. FAIR TEST Which variable will be changed? (This is the independent variable) The variable that will be changed is the concentration of Dettol. How will the independent variable be changed? We will change the variable by diluting the Dettol with drops of water. Give a suitable range of values for this variable Concentration of 1, 1:10, 1:100 and 1:1000
3. FAIR TEST Which variable will have to be measured or observed in order to get some data or information from the investigation? (This is the dependent variable) We will measure how much bacteria died around the filter paper. How will the dependent variable be measured or observed? By using a ruler to measure the clear zone from the center of the filter paper
2.    Other variables that need to be controlled to make your results more accurate.
Other variables	Describe how this variable will be controlled or kept the same.
Pepper corn extract	By applying amount of pepper coen extract on ech agar
Tempreture of incubater	By keeping the incubator at 20c
Size of filter paper	By making sure each agar 4 of the same size fliter paper
3.    How will you ensure that your results are reliable?  By following the method exactly and comparing the results with other groups results
4.    Notes from your trials.

Now use the information on this planning sheet to write a detailed step-by-step method.

Method:

 Step 1:

 

 Fist we made the diluted solution of dettol.

1. 10 drops of dettol (1)
2. 1 drop of A, 9 drops of water (1:10)
3. 1 drop of B, 9 drops of water (1:100)
4. 1 drop of C, 9 drops of water (1:1000

 Step 2:

1. Hole punch filter paper x4
2. place in spotting tiles

Step 3:

1. Spread bacteria (corn pepper extract) evenly around agar plate
2. Vivid on agar plate 4 sections
3. Place filter paper in the center of each section

 ( Safty note)

Each time you pick up a filter paper from the spotting tile you need   to sanitize your twezzers

Step 4:

1. Cellotape sides
2. Lable side 

Step 5:

1. Place upside in incubator at 20c
2. Get results from two other groups to compare results after atleast one day.

 Changes made to the method after the investigation started.

	Through the trials we found that pepper corn extract produced better results than youghurt, this is becasue is was a thinner substance that youghurt.

 

Recorded data:

 Trials:

Area:	1	2	3		AV
A	20	6	6		10.6
B	7	2	2		3.6
C	3	3	3		3
D	2	1	2		1.6

Processed data

Interpretation of data:

This data showed…

This data shows that the area section with the higher concentration of dettol has less bacteria growth.

Conclusion: I conclude…

I conclude that dettol is a great substance to use and that the less dettol there is the more bacteria grows. We can see this in the graph becasue the data shows that on average there is more bacteria in the lower concentrations. However the results show that bacteria can grow in a higher concentration section.

Discussion and Evaluation of the Method and Data.

 Dettol is an antiseptic and disinfectant which is used for skin disinfection. The active ingrediant is chloroxylenol, which makes up 4.8% of dettols mixture. Chloroxylenol kills bacteria by stopping the ATP from producing in the bacteria, meaning the bacteria can no longer survive and starves to death. Dettol gets into the bacteria by breaking the capsule, this means the bacteria is no longer protected. Then the dettol breaks past the cell wall, this is what keeps the structure of the cell. Then the dettol breaks through the cell membrane, this is what controls what enters the cell. Finally the dettol gets to the ribosomes, this is where the proteins are made. From here the detol kills the ribosmoe and causes the bacteria to starve and die. Even though in the first trial we used youghurt the results still showed that the higher concentration had less bacteria, this shows that even if we use a different bacteria the results will stay the same. Also in the graph it shows that even with the differences in results, on average there is still a decrease in bacteria through out the sections.

In my hypothesis I wrote that the higher the concentration of dettol the less bacteria would grow. My hypothesis was almost correct apart from in 2 of the 3 results I got. Section C had a bigger clear zone that section B. This is unusual becasue the clear zone of the higher concentration should have been bigger than the lower concentration like in results 1. If i were to do this again I would want to have compared my results with more than 2 others to get a better idea of what the outcome would be like, therefore making my results more reliable.