Pickle+Battery+Lab

Pickle Battery Lab Shannon Fusina snf5024@psu.edu Sean Haggerty swh5085@psu.edu

This lesson is appropriate for grades 6-10 with a focus on current or "charge mobility" through fruits/vegetables containing acids. The students will construct a circuit consisting of their food items, wires, pennies, paperclips, and a red LED.

This lesson follows the state standards 3.4.7A, describe concepts about the structure and properties of matter, and 3.4.7B, relate energy sources and transfers to heat and temperature. It also covers 3.2.7B,apply process knowledge to make and interpret observations. Finally, standard 3.7.7B, use appropriate instruments and apparatus to study materials, is covered.


 * Lesson Objectives**
 * The students will be able to explain why a battery works.
 * The students will be able to create a simple circuit consisting of pickles (or other food), penny, paperclip, wire, and a red LED.
 * The students will be able to explain that the electron or "charge" flow is responsible for lighting the light bulbs.

The key ideas of this lesson are a very simple version of redox chemistry and the creation of simple circuits. The students will be building simple galvanic cells out of iron paper clips and copper pennies. These two different types of metal will act as our anode (paper clip) and cathode (penny). The paperclip is the anode as it mostly made up of steel, which has iron in a 2+ oxidation state. The details of the electrochemistry are for the most part beyond the scope of this experiment. The key point that will be used to explain the two different metals, is that the metals play "tug-of-war" with the electrons, which creates a current (in actuality current is the movement of a positive charge, but for the purposes of the experiment this is the same). The reason we use pickles and other acidic foods is because the acidity present in the food creates charges that help the electrons move from one metal to another (as well as helping to counter balance charge build-up, but this is once again beyond the scope of this experiment). Another key point of the experiment is that the types of metal must be alternated so that no two identical metals are present in a pickle or connected directly by alligator clips. This is important, as the difference in metal type produces the "battle" for the electrons. If two identical types of metal are connected to one another, there will be no "tug-of-war", as the electrons would feel equal pulls in opposite directions. The last major point of this lesson has to do with circuits. Students are building very simple circuits with a battery (the food), the wires, and the LED (resistor). The major concept being explained in this section is why a battery is able to light up flashlights and other electronic devices. This includes explaining that electrons leave the battery from the negative end and enter the positive end. Just like two different types of metal must be connected in the pickles, the batteries must have to different ends touching. The batteries will be "measured" by measuring the voltage between the pickles in the circuit. This will be compared to the voltage of an actual battery to explain why homes are not powered by food. Ammeters could also be used, but the current is so small that the measurement would not be accurate.
 * Content Explanation**


 * Administrative Considerations**

The instructor will need to make sure the students do not eat any of the food items. They must also know ahead of time if any student has allergies to any of the products being used. Also, any allergies to latex would be needed to be known.

The instructor must also make sure the pocket knife used to create the slits for the pennies and paperclips be out of reach of the students by the time the lesson starts.

For English language learners and students with exceptional needs, there will be a diagram of the circuit to better explain how it set up. They will be able to use this as a guide as it is being explained.


 * Materials (per 2 or 3 students amount listed after)**
 * 20 pickles ~2 large jars of pickles (~4 or 5 pickles)
 * 5 lemons
 * 5 apples
 * 25 clean pennies (4)
 * 1 box of large paperclips (4)
 * 12 alligator clips (5/6)
 * 2 Voltmeter (1)
 * 4 Red LED (1)
 * 2 9-volt batteries (1)
 * 2 Calculators (1)
 * Box of examination gloves


 * Equipment**
 * Small box cutter for teacher to make incision in food
 * Wax paper


 * Body of the Lesson**

a) **Engagement:** (3 min) How many of you have ever used a flashlight? Do you know how it works? How about batteries, how many of you have used a battery? Do you know how a battery works? Did you know that you can use everyday food items to light a light bulb using the same principles as batteries?

b) **Exploration/Explanation**: (these two are intermixed as multiple topics will be explored and then explained) (14 min)
 * For this exercise the students will be given a table where they can fill in how many of each food item was required to light up the LED and then determine which worked best. They will then measure the voltage of each food and determine how many of each food will be needed to create the same voltage as a battery.

Do any of you know what a "circuit" is? [Short explanation of a circuit/how it lights the light bulb and what current is.] We will now build a light bulb using the pickles to try to light the red LED. How many pickles do you believe it will take? [Have the students build the circuit each time adding a pickle until the LED lights] Why does the light bulb only light up if the circuit is connected from penny to paperclip and not penny to penny? [Short explanation of oxidation/reduction in terms they will understand. It will be explained as a type of tug-of-war of the electron between the two metals.] Are pickles the only food item that will light up the LED? [The students will then be able to attempt to light up the bulb using apples and lemons.] Which food worked the best? [The students will mark this on their paper.] We just proved that we could use food to light up an LED. Why do we not use food to power our houses? [Show and demonstrate how a voltmeter works.] We use these everyday batteries to light up flashlights, clocks, radios, and other household items. How many volts does the battery have? [Have the students measure and record.] If 1 battery produces 9 volts, how many pickles, apples, and lemons would it take to match that battery? [Have the students measure and record the data for 1 of each and then help them with dividing the amount of the battery by each food item to see how many of each would be needed.]

d) **Evaluation**: (3 min) How many volts does it take to light up the red LED? How will you figure this out? [The students will need to measure the voltage across the entire circuit of all three to find a range of volts needed depending on the average of each food circuit. This will be done without the help of the instructor.]

e) **Elaboration**: (4 min) Will the circuit work if you mix the food items or only if it is all one? What is the least amount of food items you can use using at least 2 different foods to make the LED light up?