Zinc–carbon battery

Make your own battery!

Difficulty:
Danger:
Duration:
20 minutes
Zinc–carbon battery

Reagents

Safety

  • Put on protective gloves and eyewear.
  • Conduct the experiment on the plastic tray.
General safety rules
  • Do not allow chemicals to come into contact with the eyes or mouth.
  • Keep young children, animals and those not wearing eye protection away from the experimental area.
  • Store this experimental set out of reach of children under 12 years of age.
  • Clean all equipment after use.
  • Make sure that all containers are fully closed and properly stored after use.
  • Ensure that all empty containers are disposed of properly.
  • Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
  • Do not replace foodstuffs in original container. Dispose of immediately.
General first aid information
  • In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
  • If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
  • In case of inhalation: Remove person to fresh air.
  • In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
  • In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
  • In case of injury always seek medical advice.
Advice for supervising adults
  • The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
  • This experimental set is for use only by children over 12 years.
  • Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
  • The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
  • The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
  • Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.

FAQ and troubleshooting

Why isn’t the LED glowing?

If you have assembled the two batteries and connected them to the LED via the connector, but the LED isn’t glowing – don’t worry! This is probably easy to fix.

First of all, try switching the wires. Electric current can run through a LED only in one direction. Make sure the crocodile clips are clamped to the metal, not the insulation.

Next, check all the connections. Are the parts of the circuit connected securely? The bolt must be touching the springs in the connector, and the graphite rods on the opposite ends of the batteries must be touching the metal parts of the connector housing. Finally, make sure that all the wires are fixed securely to the LED and to the connector.

If none of these steps help, try using a different LEDor try assembling a new battery.

I can’t insert the rod into the hole in the lid.

See if using a hard surface such as a table can help. Begin by inserting the graphite rod as far as you can into the hole in the plug. Then, set the dull end of the graphite rod on the table or other hard surface and use both hands to press the plug down towards the table. Use the wooden disk to help measure that 2 mm distance. Of course, you can ask your parents or another adult for help.

Is it OK to use regular batteries instead of batteries from the kit?

We do not recommend connecting regular batteries to the LEDs from the kit. This could potentially result in the LEDs overheating and/or malfunctioning.

Step-by-step instructions

For a battery to work, it has to draw electrons in with its “+” pole and pump electrons out with its “−” pole when the poles are connected via a wire. Manganese dioxide MnO2’s ability to attract electrons makes it a good material for the “+” pole. And graphite will help carry the electrons to the MnO2 particles.

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Use graphite rods to connect the MnO2-graphite mixture to the circuit.

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Now, assemble the “+” pole.

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Zinc Zn is rather good at giving electrons away, which makes it perfect for the “-” pole. The bolts are covered with a thin layer of zinc. Next, an electrolyte must go between the “+” and “-” poles. NH4Cl will allow charged particles (ions), but not electrons, to move from pole to pole.

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You’ll need two batteries to power your LED.

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Electrons travel through the wire from Zn to MnO2 to make your LED glow.

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Expected result

The battery you just made provides the LED with electrical energy. The LED lights up!

Disposal

Dispose of solid waste together with household garbage.

Scientific description

How do zinc–manganese batteries work?

A manganese battery (zinc-manganese battery, zinc-carbon battery) is a chemical source of electric current that relies on an oxidation-reduction (redox) reaction between manganese dioxide (MnO2) and zinc powder (Zn). A redox reaction involves the transfer of electrons from one element (the reducer) to another element (the oxidizer).

Our battery is divided into two sections, separated by wadding: one section holds the oxidizer MnO2 and the other contains the reductant Zn. When the battery is not connected to anything, these isolated substances cannot react with each other. But when the crocodile clips are connected to a diode, the circuit is closed and the reaction can begin: electrons start migrating from the zinc section to the manganese section. They move through the foil, then through one terminal and the black wire to the diode (which starts glowing!), then continue on through the red wire, and finally through the graphite rod to the manganese dioxide (MnO2) section.

Why do we need the graphite powder?

The battery will work only if the electric current can flow “unobstructed,” so the agents inside the battery must be able to conduct electricity very well.

Unlike graphite, manganese dioxide MnO2 is not a good conductor, but a mixture of MnO2 and graphite powder is a fine conductor for such a battery.

Why do we need the NH4Cl solution?

As electrons move from the zinc section to the manganese dioxide section, they create an electron excess in the latter. Meanwhile, an electron shortage arises in the zinc section as electrons move away from it. These must be balanced for the battery to work long and reliably.

Ammonium chloride NH4Cl is primarily intended to be a source of protons H+ that can balance out the electron excess in the manganese dioxide MnO2 section.

At the same time, chloride anions Cl- balance out the electron shortage in the zinc section.

Also, on the zinc side, the reaction creates Zn2+, which readily forms insoluble compounds in these conditions. If these compounds accumulate, the electric current will eventually just stop. Once again, ammonium chloride comes to the rescue: the ammonia NH3 obtained during the reaction forms a compound with Zn2+ that is easily soluble in water.

That's interesting!

Who invented the manganese battery?

Many prominent minds of the early 19th century were dedicated to the problem of a chemical power cell. One of the first steps towards a chemical manganese battery was the creation of the voltaic pile by Alessandro Volta, an Italian physicist, chemist and physiologist, in 1800. It was the first chemical source of direct current. It consisted of zinc, copper, and a cloth, saturated with sulfuric acid. This system, understandably, could not really be used in practice though.

In 1836, John Daniel, a British physicist and chemist, invented the first chemical power cell that could be used in a practical application – the Daniel cell. It consisted of two connected pots: one containing a zinc Zn plate plunged in zinc sulfate (ZnSO4) solution; another one containing a copper Cu plate plunged in copper sulfate (CuSO4) solution. Zinc was the reductant and copper was the oxidant. Electricity ran through the wires that were connecting the plates.

The first “salt” battery was invented by Georges Leclanché, a French chemist and inventor, who lived and acted in the middle of the 19th century. At the same time, it was the first dry cell ever. Though it has some chloride ammonium solution inside, it’s very little and is absorbed by the other reagents. That was a real breakthrough – no pots with fluid solutions were needed for battery operation, thus, batteries became compact and portable. Leclanché’s own battery, which was named after himself, was invented and assembled first in 1865. Leclanché’s chemical cell was virtually identical to the battery we have assembled in this experiment.

What is the difference between zinc-carbon and alkaline batteries?

The principal difference between zinc-carbon and alkaline batteries is the type of electrolyte used to assemble the battery. As we already know, in the case of a zinc-carbon (or “salt”) battery it’s ammonium chloride NH4Cl. This agent is a salt – which is where the name “salt battery” sometimes comes from. In alkaline batteries alkali solution is used – alkali metals hydroxide (Li, Na, K). Usually, potassium hydroxide KOH is used, less frequently are NaOH and LiOH. Battery structure is also diverse. Alkaline batteries generally work longer than “salt” batteries.

How to tell a “salt” battery from an alkaline battery in a shop?

“Salt” and alkaline batteries have different markings. Battery marking (a few letters or numbers on the housing that let us distinguish various battery types) usually consists of one or two letters and numbers. Numbers designate battery type in terms of the shape and size. Everyone has heard of “Mignon” or “triple-A” battery types. They are marked with numbers 03 and 6 respectively. The numbers are preceded by the letters; R for “salt” batteries and LR for alkaline batteries. For instance, an alkaline battery will have the marking LR03. Lithium batteries are designated by the letters CR. If you have a battery with the two first letters SR or PR – you are lucky! This means you hold a rare silver or zinc-air battery.

What devices can be powered by zinc-carbon batteries?

Generally speaking, any device that needs electric power can run on zinc-carbon batteries. However, a small battery would not be enough to power say a fridge or a washing machine. The scope of zinc-carbon batteries is small gadgets, such as flashlights, motors in toy cars, clocks or watches.

The zinc-carbon battery that we have assembled can power a LED, a watch or a small calculator. For the stable work of such gadgets we need just a small amount of electricity.

Can our battery be recharged?

Zinc-carbon batteries as well as alkaline batteries cannot be recharged and our little battery is no exception here. Chemical power cells that can be recharged with electric current are called accumulators. The main difference between the accumulators and non-rechargeable batteries is that the chemical processes in accumulators have the ability to be reversed which happens under the influence of electric current.

Never confuse rechargeable and non-rechargeable batteries. They look similar and have the same shape, since they are intended for use in the same devices. Be careful with this “non” prefix; it determines if the battery can or cannot be recharged!

More details

Why can we not recharge a zinc-carbon battery? To recharge an energy cell, it’s necessary to run electric current through it. If we try to do it with a regular battery, the first thing to happen would be the decomposition reaction of water H2O to oxygen O2 and hydrogen H2:

2H2O + 2e- → H2 + 2OH-

2H2O – 4e- → O2 + 4H+

Or entirely:

2H2O → 2H2 + O2

The gases that come out would simply rip the battery to pieces. Do not try to recharge a zinc-carbon battery! It’s not only pointless, it’s dangerous as well!

How long can a battery work?

Usually, a battery similar to the one we have assembled in our kit provides sufficient energy to make the LED glow intensively for 2-3 hours. If you make an effort and assemble it very accurately, such a battery could work for up to 10 -12 hours!

What is the difference between our battery and a battery from a shop?

In terms of chemistry, our battery is exactly the same! The main difference is in construction of the battery. In a manufactured zinc-carbon battery oxidant (MnO2) layers and reductant layers (Zn) are much thinner, but they are wide and the surface of the membrane (which in our case is wadding) is much bigger. Such a battery can produce higher current than ours which is why it’s suitable for various devices (powerful flashlights, remote controls for TV, kids toys, computer mice). Furthermore, such a battery is airtight and that’s why the electrolyte (ammonium chloride solution NH4Cl) inside does not evaporate. In our case, electrolyte solution evaporation is the main cause for our battery running down quickly.