Download Pickle Juice - Lesson Corner

Pickle Juice
Grade: K-12
Unit: Physical Science
Topic: Conductors of
electricity
Time frame: 1-2 45
minute periods.
Equipment: Voltage
sensor
Science skills:
Hypothesis
Measurement
Design
Purpose:
Students will “plug into” a pickle and measure the voltage drop across the
electrodes. This value will then be compared to a variety of other conductors
chosen by the students.
The Plan:
Set the Stage
Ø
Present a discrepant event. Connect a nail to each section of a twoconductor lamp cord. Stick the nails into each end of a large whole pickle.
Plug the lamp cord into a wall socket. Be Careful. After a few seconds of
sizzling, the pickle will begin to glow. Darken the room to get the best effect.
Ø
Encourage students to question what makes the pickle glow.
Pickle Plug In
Connect nails to cord parts.
Wrap the exposed wire in
black electrical tape.
Stick the nails into the pickle
end, but DO NOT let the nails
touch.
Carefully plug into wall outlet.
Develop the Concept
Ø Connect a circuit as shown. Use a 1.5-volt light bulb and battery.
Ø Ask students why the light bulb does not glow.
Ø Connect a wire across the two nails.
Ø Ask students why the light bulb now glows.
Ø Pour distilled water into a glass and put the electrodes (nails) into the water.
Add a little salt, just enough to make the light bulb begin to glow.
Ø Replace the water in the glass with pickle juice, of stick the electrodes into a
lemon. Encourage students to think of other things that may act as
conductors of electricity.
Generate the Experimental Question
Students may want to generate their own experimental question the day before
experimentation. This will enable them to bring materials to measure.
1. Do all fruits conduct electricity equally?
2. How does the voltage drop across water and one teaspoon of
salt compare to the voltage drop across the same amount of
water and two teaspoons of salt?
3. Does vinegar conduct electricity as well as salt water?
4. Is the voltage drop across warm salt water the same as across
cold salt water?
Before beginning their experiment, students should write their experimental
questions and simple procedure outline.
Procedure/Activity Suggestions
Suggestion I (What is the voltage drop across different conductors?)
1. Connect the circuit as shown in the above diagram but use a 100-ohm
resistor in place of the light bulb. (Try other values of resistors, too.)
2. Stick the electrodes in a conductor like a pickle, lemon, solution, etc.
3. Measure the voltage across the battery, resistor, and electrodes.
4. Change the conductor and measure again.
Suggestion II (What is the change in voltage when salt is added?)
1. Connect the circuit as in Activity I placing the electrodes in distilled water.
2. Add one teaspoon of salt and measure the voltage across the resistor.
3. Continue adding one teaspoon of salt and measuring until the value does not
change.
4. Graph and interpret the results.
Suggestion III (Does temperature have an effect on voltage?)
1. Make a conducting solution. Heat it until it is very hot.
2. Connect the circuit and place the electrodes in the solution.
3. Measure the voltage across the resistor.
4. Continue measuring the voltage as the solution cools.
Assessment:
Ø Students should be able to explain the procedure they used for taking the
measurements. They should also be able to defend their choice of
measurement.
Ø Students should be able to generalize their results to explain the
phenomenon.
Ø Students should be able to describe how they managed their control variables
to assure that they were held constant.