Unit 36 Laboratory Activity: Acids, Bases, and the release of gas
Goal: Make an acid-base indicator and use it to measure the acidity of common substances.
Equipment and Materials:
- A chunk of red cabbage (¼ to ½ head)
- Pot and water to cover grated cabbage
- Glass canning jar with lid (should be able to handle boiling water).
- White vinegar
- Baking soda
- Dishwashing detergent
- Grate the cabbage into the water.
- Boil the mix until the water turns dark purple (20-30 minutes).
- Pour the mix through the strainer into the glass jar. You now have an acid-base indicator containing a pigment, anthocyanin. You can make litmus paper by soaking strips of coffee filter in the liquid and letting them dry.
- Add some drops of cabbage solution to the white vinegar. What happens to the color?
- Add some drops of cabbage solution to a solution of baking soda and water. What happens to the color?
- Add some drops of cabbage solution to a solution of dishwashing detergent and water. What happens to the color?
- Try some other solutions made from common foods or household compounds such as soaps or cleaning fluids.
- If you change the procedure, describe the materials you used and the steps that you actually followed.
- Make a table of your test results. List the substances you test and record the color for each one. Can you make a range of colors? What substances test out for similar colors?
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