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Acid-Base Behavior of Kitchen Chemicals 

PURPOSE

Determine whether various kitchen chemicals are acidic, basic, or neutral.
 

PERFORMING THE EXPERIMENT

1. Place a single strip of Galaxy Gold test paper in your tray.
   
   
2. Using the wood splint provided in each test tube, place one drop of each solution onto separate areas of the test paper.  Return wood splints to the correct test tubes.
   
   
3. Observe the color of the test paper both before and after the drop hits the paper. 
   
   
4. Determine whether each solution is acidic or basic.  (see "Explanation" below) 
   
   
5. Record your results on the table provided. 
   
   
6. Please be certain to return each wood splint to the correct test tube so that no contamination takes place.
   NOTE:  Neutral solutions may leave the paper in its original golden yellow or yellow-orange color. Therefore, you have not distinguished acidic solutions from neutral solutions thus far.
   
   
7. Prepare red indicator paper by placing several drops of sodium bicarbonate (baking soda) solution on the strip of paper.  What happens?  Why? 
   
   
8. Let that strip of paper dry, and then use it to test the solutions that you thought were acidic in tests above. Record your results.  Do they all turn the red paper back to yellow-orange?  If any do not, they may be neutral solutions which will leave both the golden yellow paper or the red paper the same original colors rather than causing a change.
   
   
9. Place all used indicator paper in the container marked USED INDICATOR PAPER. 
    
   

QUESTIONS TO THINK ABOUT

1.  Which of the kitchen chemicals do you regularly eat or drink?  Do you usually eat or drink primarily   neutral and acidic substances, or primarily neutral and basic substances?  On what occasions do you eat or drink the other one?  Why?

2.  Based on the original color of goldenrod indicator paper direct from the package, is the atmosphere in which we live slightly acidic or slightly basic?  What substance in the air causes this behavior? 
 

EXPLANATION

Acids have a sour taste and often turn various indicator papers one color whereas bases are slippery and have a bitter taste and often turn the same indicator papers another color.  There are many indicator papers that are available or can be made.  To determine the acid-base behavior in this experiment, you use Goldenrod Indicator Paper (Wausau Papers Astrobrights Galaxy Gold WAAB57A).  The dye which gives "goldenrod" paper its characteristic color is called C. I. Direct Yellow 4.  This dye remains yellow-orange in the presence of acid and turns bright red in the presence of base.
 

EQUIPMENT NEEDED

Test tube rack; test tubes containing various kitchen chemicals; strips of Wausau Papers Astrobright Galaxy Gold WAAB57A indicator paper; wood splints or droppers for each test tube; trays for holding the solutions; data sheet on which to record results;  container marked USED INDICATOR PAPER.
 

REFERENCE

Modified from "Goldenrod Indicator Paper", Institute of Chemical Education, University of Wisconsin - Madison; presented at the NSTA 1993 Spring Convention in Kansas City 

Kids Involved Doing Science is at http://www.kids.union.edu

Modified 02/22/2001 by C. & P. Scaife.