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Determining Acids and Bases With Homemade pH Indicator Strips Made With Red Cabbage Juice Period 0 IB Chemisty
Annie Truong
Ms. Tran

Purpose: The purpose of this lab is to make homemade pH indicator strips using red cabbage juice as the main ingredient and estimate the pH of different substances with these strips. Background Information: Acids and bases have properties of modifying the color of certain substances. The juice of the red cabbage is a blue-violet color and when it comes in contact with acidic substances it becomes red and when it comes in contact with basic substances it becomes green and sometimes yellow when it is very strong. A pH indicator is a halochromic chemical compound that is added in small amounts to a solution so that the pH of the solution can be determined visually. The pH indicator is a chemical detector for hydronium ions or hydrogen ions. The color of the solution to change depending on the pH. Red cabbage juice contains a natural pH indicator that changes colors according to the acidity of the solution. Red cabbage contains a pigmented molecule called flavin. Very acidic solutions will turn anthocyanin a red color. Neutral solutions result in a purple color. Basic solutions should appear greenish. Acids are substances which when added to water produces hydrogen ions and bases are substances which when added to water produces hydroxide ions. Hypothesis: If I make a pH indicator strip using red cabbage juice as the main ingredient, then I can get an idea of what the pH level would be of different substances because the red cabbage juice contains a natural pH indicator that changes color according to the pH of the solution. The dependent variable would be the color of the cabbage paper and the independent variable would be the type of substance used. The control of this experiment would be the amount of cabbage juice and or substance. Materials:

1. ½ of a red cabbage
2. 1 pot
3. 4 cups of water
4. 1 stove
5. 1 knife and cutting board
6. 1 large bowl
7. 1 large art paper
8. 1 pair of scissors
9. 20 mL of vinegar
10. 20 mL of tap water
11. 20 mL of lemon juice
12. 20 mL of milk
13. 20 mL tap water
14. 20 mL soap
15. 20 mL shampoo
16. 20 mL Coca-Cola
17. 1 aspirin tablet & 20 mL of water
18. 3g baking soda & 20 mL of water
19. 1 pair of chopsticks
20. 1 strainer
21. 1 baking tray
22. 6 paper towels
23. 10 xSmall containers/plates
24. Small medicine cup with 10mL mark on it
25. Grams kitchen scale

Part A
1. We took the red cabbage and put it on the cutting board. Then we used a knife to cut the cabbage into slices and placed them into a pot. 2. We added enough water to cover the slices which was about 4 cups and we placed it on the stove. We left the heat on medium high and let it boil for around 30-45 minutes. We recorded our observations on the cabbage and color of the water. 3. Fifteen minutes into the boiling process we recorded our observations. 4. After 30-45 minutes we turned the stove off and let the cabbage juice cool down. 5. We took the strainer and placed it over the bowl. We then took the pot and poured the cabbage and juice into the strainer. We recorded our observations on the juice and cabbage. 6. We placed a little bit of the juice onto a plate in three different sections. In one section we put a little bit of vinegar and in another we put baking soda on it. We recorded our observation. 7. After that we took our art paper and cut it into 6 pieces that is big enough to fit into the bowl and we let the papers soak in the juice for half an hour. We recorded our observations on the paper before and after we placed it into the water. 8. We took our baking sheet and lined it with the paper towels. 9. After that we took the papers out with our clean chopsticks and placed it onto the baking sheet....
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