Introduction:

In this lab students are introduced to the concept of acids and bases. Students have the opportunity to test a variety of home substances in an indicator solution of cabbage juice. From this testing and observation students will begin to grasp the concept of acids, bases, concentration and titration.

Students will be working in teams of three-four for this lab and will have 3 -4 forty minute sessions to complete the lab. Students may "go beyond" in this lab by testing their own household mystery substances and writing up the results.

This lab has been adapted from the GEMS hall of science "of cabbages and chemistry"

Materials needed:

Solutions of household chemicals such as: water alcohol lemon or lime juice aspirin salt water vinegar vitamin C tablets baking soda drain cleaner tummy tablets coffee tea

Cabbage Juice or other indicator solution Other equipment needed: Eyedroppers small paint mixing trays or egg crates plastic cups for the solutions safety goggles or glasses colored pencils or crayons paper to record your answers

Safety considerations:

You will be using acid and base solutions. It is important that you wear your safety goggles and aprons for this lab.

You must wash your hands with lots of water after this lab to remove any chemicals from your skin.

Do NOT taste any of the liquids in this class. Only smell the chemicals by wafting them as you have been shown.

Session One:

Using the cabbage juice indicator solution and the substances provided, try to determine a pattern of color change that allows you to distinguish between and acid and base solution.

Be sure to record your procedure and materials list on a separate sheet of paper. Keep track of your data on the sheets provided, in class or make your own.

At the end of session one we will gather as a class to discuss your results.

Session Two:

In this session we will be using the cabbage juice as our indicator again, only this time we will be trying to determine the concentration of the various acids and bases that we have to test.

Your challenge is to balance each acid and base so that the resulting color in your tray is blue. This process is called titration. Is careful not to overfill your containers or to cross contaminate your solutions. The specific directions for this part are on the data sheets.

Keep track of your data on the sheets provided, in class or make your own.

Session Three:

To go beyond. (for an A grade, complete one of the activities below.)

A. If you group has time bring in a variety of common household substances and use the cabbage juice to test for concentration and strength. Not everything you bring in will be an acid or a base, you might surprise yourself! Be careful not to mix strong acids and bases, they can react by producing noxious gases.

You may also choose to complete this lab at home, cabbage juice is made by boiling chopped up red cabbage until the color has come out of the leaves. Just be sure not to stain anything with the juice.

B. Your group may want to experiment with other natural indicators such as flower petals, grape juice, strong tea solution or turmeric spice.
You any also try this experiment with commercial indicators such as phenol red, and record your results.

C. Ever dyed eggs? You were using acid or basic solutions that had been colored with indicators such as the ones mentioned here. Try creating some dyed eggs and explain the chemistry of why you think this works.

D. How could you use this technique to determine the pH of soil?
Design a procedure to test soil Ph using cabbage juice as the indicator. Are there any signs of pH level that occur in plants you find growing in your yard or neighborhood? Describe.

Discussion Questions:

Having completed the investigations and data sheets for this lab, you should now have a good picture of the concept of acids and bases. Try to answer these questions as a group to check and confirm your knowledge.

1. Describe the way the test tubes looked when you had an acid in the tube vs. a base.

2. Why did the cabbage juice turn different colors when exposed to the acid or the base?

3. What defines an acid, base or neutral substance?

4. What is concentration? And what were you doing when you were adding drops of acid to the tube with Drano and cabbage juice? Be detailed in your answer. What chemically was happening, (we all know it changed color).

5. How are acids and bases corrosive?

6. What is Acid Rain and why is it damaging to the environment?

7. Use the knowledge that you have from the lab to suggest three ways to UNDO the damage done by acid rain (or any acid source) to lakes and streams.

8. Did anything else that you did in this lab surprise you?

9. Were any of your home substances different than you expected?

10.. How would you make this lab better for students in the future?

Need help ? check here Chem4Kids! Your Chemistry Website! at the acid and base section.

An interesting link to how all of this works water to wine.

Interested in more home labs? Check here  you can with beakman and jax
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