Stalagmites and stalactites

Year 8s were investigating solutions and as a fun practical they all created their own ‘stalagmites’.

They were all introduced to new chemical terms and investigated that in a salt solution, water is the solvent and the salt is the solute. For each solute and solvent, there is a limit to the amount of solute that will dissolve in a particular volume of the solvent. When no more solute will dissolve, we say that the solution is a saturated solution. By heating the solution and adding more solute we can prepare a supersaturated solution.

When the students added a single grain of salt to their supersaturated solutions, rapid crystallisation occurred in a spectacular way. Others pored their solutions onto a single grain of salt and watched in amazement as a ‘stalagmite’ was formed.

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