:The purpose of this experiment is to determine the specific ph represented by the various colors.Our key finding in this experiment is that as the ph grew higher or lower depending on if we either added bases or acids, respectively, it took more drops of the base or acid to change the ph of the whole solution because the concentration in the hydrogen ions grew larger or smaller depending on the material that we had put in, therefore the rate of change became slower as it progressed. The significance of this experiment is that we can relate the ph to the color after this experiment has concluded. Our major conclusion is that as the ph grew lower, the purple from the cabbage juice grew red and it got brighter as we added more drops, and as the ph grew higher, it turned dark purple, then bluish green, then yellow.
The problem is that we didn’t know that color is associated to ph, as when mr. Wong questioned everyone in the class, not one person mentioned it. When he told us we were pretty surprised because we thought that litmus paper was a special substance and that nothing else could change color when the ph was changed. It was carried out because we wanted to test whether the fact mr. Wong told us was true or not. Red cabbage juice contains anthocyanin pigment flavin, which is like a ph strip. So therefore we added bases and acids to the solution to test if it works. We expected it to change color because our teacher hinted at it, and if it didn't change color then this experiment would have been completely and utterly pointless.
We first took 100 ml of red cabbage juice, put it into a 250 ml beaker, and plunged the ph probe in. Then we took 5 ml of it and put it into a test tube. Then we kept on dripping the acid until it reached 3.4, then 2.4, then we tried to get to 1.4 but we couldn’t. Along each mark we marked the number of drops it took to get there, and we took 5 ml of the solution. Then we retried the experiment only with bases instead of acids, and got new red cabbage juice, and repeated the same thing with base except with marks at 5.4, 6.4, and 7.4. After, we recorded our results and graphed them on a plot chart.
The results and the graphs are as follows
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This is our picture of the results that we got after conducting the experiment. Because the yellow took to many drops, we couldn't count all of it so we could only display. The 5 the from the right is the original, and everything to the left is acid, and everything to the right is base.
In the acids, it took 7 drops to make the ph 3.4, 24 to make it 2.4, and we stopped after we reached 100 drops where it was 1.8.
This is the graph of the acids. It drops faster in the beginning but slows at the end.
This is the graph of the base. This shows that after 3 drops, the ph became 5.4, then after 5 more drops it became 6.4, and after 11 more drops, it became 7.4. This rate of change in ph is a lot faster than the acid change. That is because the solvent put into the solute has a higher difference in hydrogen atoms, so the average goes up quicker.
This is the graph of how it progressed. It looks remarkably like the square root function in math.
Through this activity, I have learned that ph changes color in various substances, not just litmus paper. I have also learned that as the ph gets higher or lower, the concentration of one drop of the solution will not change the ph of the cabbage juice much because the concentration of the hydrogen ions are getting closer the value of the substance that was originally added to the red cabbage juice.
