Tin dendrite

A metal tree grows before your very eyes!

Difficulty:
Danger:
Duration:
10 minutes
Tin dendrite

Reagents

Safety

  • Put on protective gloves and eyewear.
  • Conduct the experiment on the protective underlay.
  • Observe safety precautions when working with batteries.
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

I poured the solution into the Petri dish, but nothing happened.

Don’t worry! This is probably easy to fix.

First of all, make sure that the graphite plates are immersed in the solution and clamped by the crocodile clips to the walls of the Petri dish. Then, check that the batteries are inserted into the battery holder correctly – mind the polarity! If everything is OK, try using different batteries. If nothing helps, try repeating the experiment from the beginning.

The liquid isn’t covering the bottom of the Petri dish completely.

Gently shake the Petri dish, or tap its sides – this should help the solution distribute more evenly. Make sure the Petri dish is sitting on a horizontal surface.

I noticed a strange smell during the experiment – is this normal?

At the end of the experiment, chlorine forms on one of the electrodes. It is released in very small quantities, so don’t worry – it’s not dangerous at all!

The graphite plate swelled! Why?

This is normal. Ions from the solution penetrate between the layers of graphite, causing it to flake and swell.

The metal dendrite has grown – what should I do next?

Disconnect the “electrodes” and remove the batteries from the battery holder. After you take a photo of the dendrite, rinse the Petri dish with an excess of water and dispose of the dendrite with ordinary waste.

A white precipitate materialized after mixing the NaHSO4 and SnCl2. What should I do?

If the solution just became a bit cloudy, don’t worry – just continue your experiment. But if the solution is significantly altered, try restarting the experiment from the beginning.

Step-by-step instructions

Be sure to use fresh AA batteries and wear protective gloves.

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Prepare a tin chloride SnCl2 solution. NaHSO4 helps SnCl2 to dissolve in water.

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Secure the electrodes to your Petri dish.

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Pour the solution into your Petri dish. Insert the batteries into the battery holder.

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Watch a metal tree grow from the solution!

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Disposal

Dispose of the reagents and solid waste together with household garbage. Pour solutions down the sink and wash with an excess of water. The safety underlay packaging recycling code is #5 PP. Dispose of accordingly.

Scientific description

Batteries are basically electron pumps: they suck electrons in with their "+"  and pump them out from their “–” . When such a pump is connected to a solution via "electric hoses" (i. e. wires), a variety of chemical reactions take place: some particles gladly give their electrons to the "+" electrode , and some particles capture the electrons pouring out of the "–" electrode .

In our experiment, chlorine ions Cl-  (chlorine atoms with one extra electron) gladly share their electrons at the "+" electrode . Meanwhile, tin ions Sn2+  (tin atoms with two electrons missing) at the "–" electrode crave more electrons, and line up for them as soon as they appear on the “–” electrode. When accepting these electrons, tin turns from its ionic Sn2+ form to metallic Sn , forming the beautiful dendrite you see!