Fruit Batteries and fuel cell construction

Useful information
Kit List: 

Fruit
Something to power e.g. LED, small clock
Zinc rods/nails
Copper rods/nails/coins
Wires
Electrical tape

Packing Away: 

Has a mini box

Frequency of use: 
1
Explanation
Explanation: 

1. Connect the red wire on the LCD to a copper and the black wire to a zinc. Secure wires in place with electrical tape.
2. Get another copper and zinc and connect them with the connection wire using adhesive tape.
3. Insert the copper and zinc plates into the fruit to get power

How does it work?
The copper acts like the positive electrodes of a battery, as it is less reactive than zinc. When the copper and zinc plates are inserted into the lemon, a chemical reaction takes place. Electrons (extremely small particles with negative charge) move from the zinc plates to the copper to form a current, thus activating the LCD. You can replace the lemon with a potato, a grapefruit or use soft drinks or vinegar and see what effect this has.

Extra points to get across... talk about circuits a bit, why does it all have to be connecting in a circuit, how does the electricity travel through the fruit!

More advanced info - for older kids
In a battery there is a negative electrode, where electrons are produced, and a positive electrode where they are used up. The zinc is the negative electrode (anode). Zinc is more reactive than copper so gets oxidised and dissolves into the fruit juice:
Zn --> Zn2+ + 2e-

The electrons produced flow through the wires (and the LED/LCD) to the copper, which is the positive electrode (cathode). Hydrogen ions are reduced at the cathode:
2H+ + 2e- --> H2

As the hydrogen ions move through the fruit to the copper they create a current through through the fruit, completing the circuit - there are no electrons flowing through the fruit! For this to work there need to be hydrogen ions in the fruit, so it needs to be acidic. This is why lemons work well, they have lots of citric acid in. You could relate this to lemons tasting sour, which is due to their acidity. Potatoes also work as they have some phosphoric acid in, but they are less acidic than lemons so have a lower voltage (produce less electricity) - you should be able to show this using a multimeter.

Fun Facts
The development of the battery started in 1775 when a scientist called Alessandro Volta invented a machine that produced and stored static electricity by rubbing cat fur across a metal plate. A few years later, a doctor called Luigi Galvani noticed that dissected frogs' legs twitched when they were in contact with two different metals. Volta realised that the electricity came from the metals and began doing experiments with different types of metal. In 1800, he made the first ever battery which consisted of copper and zinc strips separated by a piece of paper soaked in salt water and dipped in diluted acid.

Risk Assessment
Date risk assesment last checked: 
Tue, 14/01/2020
Risk assesment checked by: 
Holly Smith
Date risk assesment double checked: 
Fri, 17/01/2020
Risk assesment double-checked by: 
Polly Hooton
Risk Assessment: 

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Hazard Risk Affected Person(s) Likelihood Severity Overall Mitigation Likelihood Severity Overall
Sharp plates/nails/forks Could hurt people/cause cuts All 3 3 9 Monitor kids when they are using metals, and make sure metals are not too sharp 2 2 4
Fruit juice Irritation if it gets in eyes. All 3 3 9 Encourage metal rods to be put carefully into fruit to prevent squirting of fruit juice.
Call a first aider if fruit juice gets in eyes, who may perform an eyewash if trained and confident to do so.
2 2 4
Fruit juice Juice is acidic and can cause damage if in contact with cuts. All 3 1 3 Clean rods between use so not covered in juice when children handling them.
Check that children don’t have uncovered cuts before starting demonstration.
Demonstrators should wear plasters over any cuts they have.
In case of accident, wash the affected area with clean water.
2 1 2
0
0
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