pH Lab

In this lab, we created a spectrum using cabbage juice. First, we created a controlled variable with just the cabbage juice, and we set aside 6 other test tubes for the acids and bases.

The control variable was a pH of 7, and was a light purple color.
For the acids, we had 3 different tubes
tube number 1 had 5 drops of HCL added, with a pH of around 3 and was a red color.
Tube number 2 had 4 drops of HCL added, with a pH of 3-4 around, and was a red-pink color
Tube number 3 had 3 drops of HCL added, with a pink-violet color, and had a pH of 4

For the bases, we had 3 different tubes
For Tube number 5, it had 10 drops of NaOH added, and it was a yellow color, with a pH of 12
For tube number 6, we added 12 drops of NaOH and it was a lime green color, with a pH of around 12-13
For tube number 7, we added 14 drops of NaOH, with a dark green color, with a pH of 13






4. Which drops (acid or base) caused a more dramatic change in the pH of the solution? Why?

In my opinion, the drops of bases caused a more dramatic change in color. I thought this because it already had a natural purple color, the change from purple to yellow is more dramatic. I think the change from purple to pinkish-red is less of a change. This change from the purple to the yellow color was a bigger change because it completely changed the entire color of the spectrum for example. I think this makes sense because of the already dark color of purple, adding the base of NaOH would have more of an effect of the color change. I think that this change was more dramatic just because of the already dark color of the purple cabbage juice. If the starting color was a lighter color, for example, red, I think that the acid would make a more dramatic change because it would become a dark red, but in this case, I think the base change was more dramatic. I think if the starting color was less of a factor, this experiment could have been easier to see which effects a neutral more; acid or base.

5. What did I learn?
I learned a lot from this lab. I learned about the whole acid vs. base idea, and how each of these acids or bases effect each of the neutral pH colors. I learned about how the pH is affected, specifically by acids and bases, or HCL and NaOH. I also learned about adding acids and bases to neutral solutions, and that it often takes a lot of a certain acid or base to create a bigger change in color. For example, we had to add a lot of the NaOH to create a distinct change between the others. At first, we added around 3, 4, or 5 drops of the NaOH but these colors were not really any different. We later had to add a lot more of the drops to get a real change between the different test tubes.

This is my interpretation of the graph of this lab. I used the pH as the x variable and put the (0,7) variable in as well.

Also, you may notice the Our own experiment sign. This specific beaker was when we tried to add bases and acids together into one test tube to see the color. I believe that we added too much base because it ended up being a yellow color, similar to the other bases. We also tried to create different colors like blue and we created this by adding the base and more cabbage juice to get a blue color. I think this makes sense because the already dark color of the cabbage juice often overwhelms the base or acid colors. 

Here are some more pictures. Here is a picture of the pH scale for reference, along with some pictures of our clean lab table. Here are more pictures