How Can Acids and Bases Be Identified?

I. Introduction : Acids and bases can be identified by using a substance that changes color when mixed with an acid or with a base. Those substances are called indicators. In this lab, you will use red cabbage juice as an indicator to test some substances to see if they are acids or bases.
II. Materials: 24 Well microplate and beral pipettes, lemon juice, ammonia, baking soda solution, boric acid solution, tap water, and other common household chemicals, red cabbage juice.
 
III. Procedures:
a. Pick up microplates. Place on a white paper. Label (on the paper) the wells for the household chemicals to be tested. These may include vinegar, lemon juice, ammonia, baking soda, boric acid, and tap water (along with others).
b. Observe the color of each liquid to be tested. In a table, record the color of each liquid. Determine the odor for each liquid. Your teacher will show you how to do this. Record the odor of each liquid in your table.
c. Fill the well of the microplate 1/3 with the red cabbaged juice for each chemical to be tested. Add a few drops of the individual chemical to be tested to the well. Red cabbage juice turns blue-green in a base and dark red or purple in an acid. Record any color changes in your table.

 

 


IV. Results :
Which of the liquids were acids?



Which were bases?



What is the red cabbage juice called?



Were any of the liquids neutral (neither acid nor base)? How could you tell?




V. Additional Activities : This activity can be expanded to use other indicators such as litmus paper, phenolphthalein, or others. Also, other household products can be tested such as furniture polish, cleaners, and fruit juice.

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