Creating stalagmites
Objective: Create a stalagmite by exploiting the rapid crystallization of an oversaturated solution
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Laboratory materials
Watch glass
Glass rod
Beaker
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Reagents
Sodium acetate trihydrate (CH3CO2Na·H2O)
Water
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Safety
Don't forget the gloves, lab coat, and safety goggles!!!
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Questions
What can you observe when the solution is added onto the sodium acetate crystals?
Can you explain what an oversaturated solution is?
Procedure
- Weigh 12.5 g of sodium acetate trihydrate in a beaker and add 12.5 mL of water.
- Heat the mixture and stir until a clear solution is obtained. Cover with a watch glass and let cool to room temperature.
- In another watch glass, place some sodium acetate crystals and slowly pour the solution over them.
- Observe what happens.
Theoretical explanation
When the solution is added onto the sodium acetate crystals, the oversaturated solution immediately crystallizes, forming a stalagmite. Oversaturated solutions contain very little liquid and a large amount of dissolved solid. This makes them unstable, and the solid tends to precipitate out of the liquid. If there is no disturbance, the solution can remain in this state for a while, but upon contact with the sodium acetate crystal, immediate precipitation occurs. Additionally, the watch glass heats up because this is a process that releases heat. This is the principle used in hand warmers.
