Experiment 2: Purple Cabbage

The purple cabbage showed much better results than the carrots. Pictures of the set-up and experiment results below. 

The slices immersed in the acid range turned more reddish, and those in alkaline bluish. The pH 2 set-up even had the vegetable pigments leached into it, and the hydrochloric acid turned red. Liquid in the pH 3 set-up turned to light purple, while that in the pH 11 set-up was light bluish grey and pH 12 set-up became green. Pictures below. 

This is why purple cabbage juice is used as an indicator for different pH levels!

Experiment 1: Carrots

Carrots are not successful! Well, not “not successful”, but unexpectedly they did not show any obvious results. However, this does not mean that the experiment has gone to waste because I can conclude that acids and alkalis do not have a visible effect on carotene. Pictures of the experiment results below.

After the 3 hours of experiment duration, I kept the set-ups of pH 2 and 12, hoping to see some change after a longer time. I left them overnight, but even after 24 hours of soaking the carrots still did not have a very visible change. 

Moving on to purple cabbage next...

Experiment Preparation

I’m in Inner Mongolia now! All the experiments that follow will be carried out in the hotel room, mainly the toilet. Materials, apparatus and procedure as follows:

Apparatus and materials: pH 2 to 6 and 8 to 12, beakers, a stirrer, latex gloves, univeral paper and goggles. Not in picture: small knife and stopwatch (my phone's stopwatch).

Vegetables that I need to use for the experiment (spinach not in picture). From left to right: purple cabbage, green pepper, radish and carrot.

Experimental Procedure:

Step 1: Cut the vegetables into slices of 3cm x 3cm.

Step 2: Wear the gloves. Measure and pour 30ml of the 11 pH values (from 2 to 12) into 11 different beakers.

Step 3: Put in 3 vegetable slices into each beaker and make sure that they are fully submerged. Start the stopwatch.

Step 4: Let the slices soak for 3 hours, and take down any observable changes at 1 hour intervals.

Step 5: Repeat steps 1 to 4 for all the other types of vegetables.

My Proposal

APPENDIX D

Science Investigative Project

Project Proposal Form

Name:

Nicole Du               (  8  )

Sec 2/13

Topic of investigation:

Effect of the environment’s pH level on the pigments in vegetables.

A	Observations made
	I know from prior knowledge that vegetables have pigments which give them different colours, some of the most common being chlorophyll, carotenoid, anthocyanin and anthoxanthin. I am keen on finding out how exactly acids and alkalis will affect these pigments. Will the colour of the vegetables change? How will it change? Do the pigments from the vegetables leach into the surrounding liquid? The pigments of the vegetables or contained within the plant cells. If pigments do leach, this indicates that a certain degree of damage has been done to the plant cell membranes since they are partially permeable membranes that do not usually allow pigments to pass through.
B	Research Question
	How does the environment’s pH level affect the pigments in vegetables?
C	Hypothesis statement
	There will be a greater change in pigments, as well as a greater amount leached from the vegetables with an increasing degree of the environment’s acidity/alkalinity.
D	A short summary of research done on the area of investigation
	Using hydrochloric acid to create the acid range of pH 2 to 6 (mixed in a lab) Sodium hydroxide for the alkaline range of pH 8 to 12 (mixed in a lab) Distilled water for neutral pH of 7 Vegetables tested: Chlorophyll à Spinach and green pepper Carotene à Carrot Anthocyanin à Purple cabbage and radish Immerse slices of the vegetables into different pH conditions for 3 hours, note changes in vegetable every 1 hour Apparatus needed à gloves, measuring cylinder, beakers, stopwatch, small knife, spinach, green pepper, carrot, purple cabbage, radish, hydrochloric acid (pH 2 to 6) and sodium hydroxide (pH 8 to 12)
E	Bibliography
	Michigan State University. (2001). Vegetable cookery. Retrieved from https://www.msu.edu/~lentnerd/NewFiles/veggies.html

June Holidays: SIP in Inner Mongolia

I am going to fly to Inner Mongolia soon (on 5^th June) to visit my father (who is stationed overseas). Then I remembered that he is stationed there to commission a chemical plant (he does liaising, not engineering), and surely there would be a laboratory and a range of chemicals? I asked my father whether I could use the lab (i.e. borrow apparatus, equipment and chemicals). After some checking and asking on my behalf, my father told me that yes, they could provide me with the all those, BUT I could not actually use the lab. Or actually step foot into the plant because there were age restrictions.

Still, this is good because I will be able to get my hands on concentrated hydrochloric acid and sodium hydroxide, diluted to form pH 2, 3, 4, 5, 6, 8, 9, 10, 11 and 12. (Distilled water for pH 7.) Though it is sad that I miss the chance to actually try diluting the two chemicals myself (under adult supervision of course).

Testing pH

During the first week of June hols, I went to school but the lab was closed, however, I managed to borrow universal indicator liquid from the lab.

Together with Chin Ying, my partner, I went to buy vinegar, baking soda and distilled water. At her house, we tested out the pH of these substances using the indicator. I realised that vinegar and baking soda are rather weak acid and alkaline and cannot be used to recreate the pH scale. I also tried different types of soaps and detergents, as well as bleach. While detergent could reach a high pH of 11, I need a transparent liquid as any colour in the liquid may affect the pigments in the vegetables. Surprisingly, soaps and bleach were acidic! (About pH 4) Really puzzling. Perhaps the bleach was “fake bleach”.

Back at home, I continued to test two more types of bleach. One was an alkaline, pH 9 (quite weak and like baking soda), the other once again acidic.

Pilot Test

Instead of doing flowers, I will make the subject of my experiments vegetables instead. They are much more easily obtained and a variety of pigments can be found. I have pilot tested my experiment by immersing a lettuce leaf in vinegar for about 3 hours. The problem now is that the pigments from the lettuce leaf did not leach into the vinegar. This might be due to:

1.     Lettuce leaves do not have a lot of pigment.

2.     Vinegar is not strong enough to damage the cell membrane of the cells in the leaf to allow the pigment (chlorophyll) to leave the cells.

Due to the results of this mini experiment, I have decided to observe the changes in colour of the vegetable itself rather than the acid/alkaline, seeing as the pigments are not so easily leached from the vegetable. However, this means that my experiment is not quantifiable!

I will thus be testing the effect of pH value on pigments in vegetables. For anthocyanin, which is the red/blue/purple pigment, I will test on radish and purple cabbage. Then for carotene, which supplies the orange colour, I will use carrot. Lastly, green pepper and spinach to represent chlorophyll, the green pigment. 

I intend to recreate the pH range using vinegar and dissolved baking soda, by using different concentrations and also mixing them. The more diluted the vinegar and dissolved baking soda, the weaker they are as an acid and alkaline respectively.