Lemon Battery

How it works- the chemistry behind it

Batteries are a store of chemical energy that is quickly converted into electrical energy when the battery is wired up. Most batteries contain reactive metals. These metals give up electrons. A simple lemon battery can be constructed using a lemon, iron nail, a copper strip, wire and a galvanometer. This setup is shown on the right.

The needle on the galvanometer is deflected when the wires are connected indicating that electrons are flowing from the iron nail to the copper.

What is happening?
In a lemon battery, both oxidation and reduction reactions occur. Oxidation is a reaction that produces electrons while reduction is a reaction that uses up electrons.

The electrode where oxidation takes place is negative and is called the anode. It is the site of electron production.

The electrode where reduction takes place is positive and is called the cathode. It is the site where electrons are used.

At the anode, metallic zinc is oxidized, and enters the acidic solution as Zn²⁺ ions:

Zn → Zn²⁺ + 2e-.

At the copper cathode, hydrogen ions are reduced to form molecular hydrogen:

2H⁺+ 2e- → H₂.

1) Electrons travel around an in the lemon external circuit internal circuit acid solution in the lemon

2) Electrons are given away by the copper metal acid in the lemon zinc metal

3) Electrons are taken by the lemon juice zinc metal hydrogen ions in the lemon

4) What is formed at the anode hydrogen gas copper ions zinc ions

5) What is formed at the cathode hydrogen gas copper ions zinc ions

6) An oxidation reaction involves the giving of electrons the taking of electrons the taking of hydrogen ions the giving of hydrogen ions

7) Oxidation always occurs at the lemon surface positive terminal negative terminal

8) Reduction occurs at the lemon surface positive terminal negative terminal

9) The negative terminal is called the anode cathode electrolyte

10) The positive terminal is called the anode cathode electrolyte

11) The lemon battery will continue to produce a current of electrons until the wire heats up the zinc electrode has been used up the electrolyte dries up

12) Why would a more reactive metal produce a greater current?