Experiment Mineral Precipitation
Download printable Experiment Sheet here.
Water has many special properties. Due to its polar nature, water readily reacts with some minerals to pull them apart, and dissolve them into the water as a solution. Salt or halite. for example, is sodium chloride, and in water both elements are dissociated into the water and remain in solution - but can't be seen.
When we add a gas like hydrogen sulfide or carbon dioxide, we make the water's ability to dissolve even stronger by changing its acidity. Acidic water commonly forms from rainwater falling through the atmosphere which dissolves some CO2. This mixture is capable of dissolving limestones and calcite to make caverns. But those rocks form again as new stone, in the form of stalactites, stalagmites and flowstones.
In this experiment we see that minerals that have been dissolved can also reform through mineral precipitation. Here we use sugar to represent minerals which crystallize out of water as we make rock candy.
Sugar is not a mineral, but behaves similarly. You can use salt if you like for less sweet results.
Sugar (or salt if preferred)
- Stir sugar into warm water (to dissolve the sugar and create a solution) and bring to boil.
- Attach clothes pins to sticks and place on top of jars (so that the stick is inside the jar but the clothes pin is not)
- Pour the solution into the jars and wait.
- Observe (and taste) the results
Questions to consider:
- How is this process representative of what happens in nature?
- Where do you think this happens in nature?
- Have you every seen an instance in nature where it looked like this happened?