Paragraph on red cabbage juice (chemistry )
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In the laboratory, pH paper and chemicals are commonly used to indicate pH. In the homeschool, students can make their own pH indicator using red cabbage juice, which changes color in the presence of an acid or base. The plant pigment anthocyanin is the active ingredient responsible for the color change. In this activity, students make a pH indicator from red cabbage juice and then use it to test various substances.
Materials
Red cabbage leaves200 mL waterBlenderStrainer250-mL beaker or clear containerMedicine droppers (1 per test substance)Sheet of white paper50-mL beakers or clear containers, (1 per test substance)1 mL vinegar1 mL household ammoniaTest substances, 1 mL of each (e.g., lemon juice, fruit juice, milk, detergent, soda, antacid tablets, baking soda)
Procedure
Put on apron, gloves, and eye protection.Chop up several red cabbage leaves.Place the leaves in a blender and add 200 mL water.Blend the mixture and then pour it through the strainer into the large beaker or container. The red cabbage juice indicator is now ready for use. Note: If you use distilled water the indicator will have a reddish purple color and if you use tap water the indicator will have a violet blue color.Fill each of the small beakers or containers with 10 mL of indicator. Place them on the white sheet of paper.Add a few drops of vinegar to one container and a few drops of ammonia to another. Vinegar is an acid and ammonia, a base. Vinegar turns the indicator red and ammonia turns it green. Use these 2 samples as references for the other test substances.Test each substance by adding a few drops of it to a container of indicator. To test an antacid tablet or other solid, crush it, dissolve it in water, and add a few drops of the resulting solution to a container of indicator. After testing all the substances, students’ results should display a beautiful array of colors ranging from green to blue green, blue, violet, and red.
Materials
Red cabbage leaves200 mL waterBlenderStrainer250-mL beaker or clear containerMedicine droppers (1 per test substance)Sheet of white paper50-mL beakers or clear containers, (1 per test substance)1 mL vinegar1 mL household ammoniaTest substances, 1 mL of each (e.g., lemon juice, fruit juice, milk, detergent, soda, antacid tablets, baking soda)
Procedure
Put on apron, gloves, and eye protection.Chop up several red cabbage leaves.Place the leaves in a blender and add 200 mL water.Blend the mixture and then pour it through the strainer into the large beaker or container. The red cabbage juice indicator is now ready for use. Note: If you use distilled water the indicator will have a reddish purple color and if you use tap water the indicator will have a violet blue color.Fill each of the small beakers or containers with 10 mL of indicator. Place them on the white sheet of paper.Add a few drops of vinegar to one container and a few drops of ammonia to another. Vinegar is an acid and ammonia, a base. Vinegar turns the indicator red and ammonia turns it green. Use these 2 samples as references for the other test substances.Test each substance by adding a few drops of it to a container of indicator. To test an antacid tablet or other solid, crush it, dissolve it in water, and add a few drops of the resulting solution to a container of indicator. After testing all the substances, students’ results should display a beautiful array of colors ranging from green to blue green, blue, violet, and red.
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