Perry, Jean M. Oakton Elementary School
Evanston, IL

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
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