Fruit+Batteries

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 * Using fruit to generate electricity**

Most of the fruit and vegetables we eat could also be used to make electricity. = Tools & Materials = = Instructions =
 * 3 - 6 pieces of fruit and vegetables (for example: lemons, apples, potatoes, etc.)
 * 6 pieces of copper wire
 * 6 pieces of zinc plate
 * 1 red light emitting diode (LED)
 * 12-14 connection wires in red and black with alligator clips on the ends
 * Multimeter
 * Firstly roll the fruit to free up the juice, this helps to make the fruit juices react with the metal plates.
 * In each piece of fruit insert one piece of copper wire and at the opposite end insert one piece of zinc plate


 * Connect the multimeter to each piece of fruit by placing the the red probe on the copper wire the positive (+) terminal and the black probe onto the zinc plate the negative (-) terminal. Check the voltage output, it will be very weak


 * Join two pieces of fruit together and test the voltage output
 * Join several pieces of the fruit together by using the connection wires and test the voltage output




 * Connect the fruit battery using the connection wires to a Light Emitting Diode (LED) red to the positive longer leg of the LED and black to the negative shorter leg.


 * How many pieces of fruit do you need to make the LED light up?
 * Does it make a difference if the copper wire and zinc plate are inserted deeper into the fruit?
 * How long will the fruit generate electrical power?
 * What if the piece of fruit has come from the fridge, does this make a difference to the voltage output?
 * What if the piece of fruit is heated up in the microwave, does this make a difference to the voltage output?

= How the Fruit Battery Works = When the zinc-plate comes into contact with the malic acid in the apple, it starts two chemical reactions. In one reaction, called oxidation, the acid begins to remove the zinc atoms from the plate. Two electrons are then removed from each zinc atom, giving the zinc atom a positive charge of two.

These charged zinc atoms, called zinc ions, remain in the apple and darken the area near the screw after some time has passed. The other reaction, called reduction, focuses on the positively charged hydrogen atoms, or hydrogen ions, in the malic acid near the zinc plate.

These ions accept electrons released by the oxidation reaction and form hydrogen gas, which can sometimes be seen bubbling out around the zinc plate. The hydrogen ions are called oxidation agents, because of their tendency to remove electrons from the zinc.

These two reactions continue as long as the zinc-plate is in the apple and there is zinc material remaining. They do not depend on the presence of copper or any other material. The important thing to realise is that electrons are being released from the zinc and being accepted by the hydrogen ions in the acid.

The copper wire is also an oxidation agent. In fact, it is a slightly stronger oxidation agent that the hydrogen ions in the malic acid. That is, it can attract many of the available electrons that are released from the zinc. But it cannot do so until there is a connection between the copper and the zincplate. When a conducting pathway or circuit is established between the zinc plate and the copper wire, the copper draws electrons out of the plate through the circuit and back into the apple through the copper wire.

This movement of electrons through the circuit is an electric current. By convention, scientists have agreed that electrons move away from the negative terminal of a battery or electric cell and through the circuit toward the positive terminal. Thus, the zinc (source of electrons) is the negative terminal in a apple electric cell, and the copper is the positive terminal.

When the circuit includes an LED, the electric current can make it light up.

The voltage of the apple electric cell comes from the relative difference in the ability of zinc and copper to give up electrons. The electric current provided by the cell depends on the quantity of electrons released by the chemical reactions, among other things.

adapted from http://www.seed.slb.com/en/scictr/lab/fruit/index.htm Reference: Snyder, Carl H. (1998). The extraordinary Chemistry of Ordinary Things (3rd ed.). (pp 258-271). New York: John Wiles & Sons, Inc. = Worksheet = = References = media type="youtube" key="AY9qcDCFeVI?fs=1" height="385" width="480" http://www.seed.slb.com/en/scictr/lab/fruit/index.htm http://chemistry.about.com/od/howthingsworkfaqs/f/coldbattery.htm @http://virtuallibrary.stao.ca/elementary-data/2100_2199/2108.htm

= Food for thought! = media type="custom" key="6747599"