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Disposal of agar with silver nitrate

Submitted by sat on 28 March 2019

Answer reviewed 27 February 2023

A more reactive metal will displace a less reactive metal from its compound. The less reactive metal will coat the surface of the more reactive metal.1 This activity is used to demonstrate a metal displacement reaction between zinc metal and silver ions with the formation of silver crystals. The silver nitrate solution is mixed into molten agar prior to setting in a Petri dish. Zinc metal is placed into the agar, where the zinc displaces the silver out of the agar. Solid silver crystals form around the zinc metal and a small portion of the solid zinc dissolves into the agar to form zinc ions. This means that you may have both silver and zinc ions in the agar.


Science ASSIST recommends the use of microscale techniques, where possible. This has the advantages of reducing the risks involved in certain activities and reducing the production of chemical waste.

A microscale reaction for copper displacing silver from a silver nitrate solution can be conducted as follows, as seen in the video ‘Silver nitrate reacting with copper wire’2:

References and further reading

1 BBC Bitesize, Introduction to displacement reactions, KS3 Chemistry, BBC Bitesize website, (Accessed February 2023)

2 Bob Worley’s YouTube, Video: Silver nitrate reacting with copper wir’, Bob Worley - YouTube (August 2018)

Royal Society of Chemistry, 2023, Displacement reactions between metals and their salts, Royal Society of Chemistry Education website,

Royal Society of Chemistry, 2023, Microscale chemistry, Education in chemistry website, (March 2007)

Royal Society of Chemistry, 2023, ‘Microscale chemistry revisited’, Education in chemistry website, (May 2012)