LIQUID CONDUCTORS

Perry, Jean M.                     Oakton Elementary School
                                   Evanston, IL
                                   1-708-492-7981
                           

Objectives
1.  Students will construct a circuit tester.
2.  Students will predict what liquids are electrical conductors. 
3.  Students will test and identify liquid electrical conductors 
    and non-conductors.

Apparatus Needed (for each group of four students)

*4 D batteries                             vinegar
*4   battery holders                       salt
*1   bulb holder                           ethyl alcohol
*8   brass electrical clips                sugar
*2   Fahnestock clips                      baking soda
*l   l 1/2V miniature bulb                 distilled water
     #20 bare copper wire as needed        tap water
     large covered containers              lemon juice
     markers                               safety goggles
     labels                                paper towels
     plastic tumblers                      activity sheet

Recommended Strategy

     This activity should follow the study of "series" and "parallel" circuits; the 
teaching of how to construct a circuit tester; and the testing of solids for their 
ability to conduct electricity. 

Advance Preparation:
-Organize materials in a shoe box or tray for each group of three to four students. 
-Test the batteries and bulbs to make sure they work.  Have replacements available. 
-Make a circuit tester for liquids and have it on display for students to use as a 
 model for making their circuit tester.  (Circuit tester should be a series circuit 
 made of four D batteries with the Fahnestock clips as electrodes.) 
-Prepare solutions of salt, vinegar, baking soda, sugar, lemon juice, and ethyl 
 alcohol in distilled water.  Use your own judgment as to the proportions; the 
 liquids need only be strong enough to light the bulb in the tester.  Store the 
 solutions in clearly labeled, covered containers. 
-Prepare an activity sheet for recording observations.  Activity sheet should include 
 columns for recording the names of liquids tested, student predictions, and 
 observations. 

Doing the Activity:

l.  Students write the names of liquids to test in chart (activity sheet). 
2.  Students predict if the liquids will or will not conduct electricity. Prediction 
    is recorded. 
3.  Circuit tester is made using teacher's tester as model. 
4.  Each tumbler is labeled with the name of one liquid. 
5.  Students are reminded to WEAR SAFETY GOGGLES. At least 3 cm of one liquid is 
    poured into the correct tumbler.  The clips of the tester are put into each 
    tumbler at equal depth and equal distance apart.  Observations are recorded. 
6.  Testing liquids will need some guidance from the teacher.  For best results, the 
    flat sides of the clips should face each other.  The liquids should not be mixed, 
    and the clips should be cleaned between tests. 
7.  Discuss:
     a.  What liquids will allow the bulb to light? 
     b.  What liquids will not allow the bulb to light? 
     c.  Does the bulb glow with the same brightness with each liquid? 
     d.  Are there any changes in the clips when you are testing? 
     e.  Did you notice anything happening in the liquid when you were testing?
8.  Record conclusions on overhead or chalkboard.

Optional Activities:
l.  Have the students repeat the activity using liquids brought from home such as 
    coffee, liquid soap, orange juice.  DO NOT USE CAUSTIC, CORROSIVE, OR POISONOUS 
    LIQUIDS. 
2.  Interested students may advance into the study of acids, bases, and salts. 
3.  Challenge students to design another type of conductivity tester. 

*These materials can be ordered from:
      Delta Education Inc. 
      P.O. Box M
      Nashua, New Hampshire 03061
      1-800-258-1302