Grow your own stalactite - yes, honestly it can be done, and it looks like an icicle, handy as a decoration for the coming festivities.
You will need:
- Salt
- Two small jars
- Large paper clips
- Wool or string
- A small saucer.
What to do:
- Stir plenty of salt into a large glass of very hot water. Keep stirring. If all the salt dissolves, add more. Allow to cool, then pour half into each jar.
- Attach a paper clip to each end of a piece of wool - about 40 cm long.
- Put one end of the wool in one of the bottles, and the other end of the wool in the other bottle. Make sure the ends of the wool are in the solution.
- Now make sure that the bottom of the loop of wool between the bottles is hanging below the level of the salt solution in the bottles.
- Place a saucer under the bottom of the loop of wool. Leave for a week.
What’s going on?
The salt solution travels along the wool by capillary action. This is a physical effect by which water can travel upwards as if to defy gravity! It is due to the interactions between the water molecules and the wool which contains tiny tubes and spaces for the solution to fill. Plants take advantage of capillary action to pull water from the soil into themselves.
As the salt solution travels along the wool it starts to drip off the lowest point of the loop of wool. The water evaporates and salt crystals are left behind. In time more and more salt solution drips down and the crystals of salt grow larger. Eventually it forms a stalactite.
Stalactites and stalagmites, collectively known as speleothems, form due to water seeping through rock. As the water moves through the rock, it dissolves small amounts of limestone or calcium carbonate. When the water drips from a cave ceiling, small amounts of this limestone are left behind, eventually leaving an icicle shaped stalactite. Limestone that reaches the cave floor "piles up" and forms stalagmites.
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