Salt Crystal Experiment


What to do on a cold, rainy day? Science experiments!

My little lady LOVES crystals, and anything to do with magic and fairies. So when I asked her if she’d like to grow some crystals she became very excited and went to get her brother for support!

Materials:

Two small cups
String (we used embroidery floss – about six inches)
Salt
Water
Screws (or nails – something to weigh down the ends of the string in the water)
Something to mix with
TOWELS, for life’s unexpected happenings.
One or two willing scientists!

This experiment is great for the younger crowd because accurate measurements aren’t necessary.

Before you get started it might be fun to taste the water and the salt and talk about how the water tastes before the salt is mixed in (well it doesn’t taste salty!), what it looks like (i.e. clear, you can see through it), and maybe do a practice stir in the plain water and talk about how easy it is to move the spoon or whisk through the water at this point. You can also take a close look at the string – is it soft or hard? Does it taste like anything? Etc.

It is time to begin the experiment. First pour the salt into the cups:

You don’t need TOO much salt – I tried to reign in my eager scientists when the salt reached about a half inch in depth.

Next, pour the water:

Again, try to stop the water from filling the cup. About half full is good.

Mix the salt and water to make a SOLUTION.

Query: What is a SOLUTION? A solution is
a.
the process by which a gas, liquid, or solid is dispersed homogeneously in a gas, liquid, or solid without chemical change.
b.
such a substance, as dissolved sugar or salt in solution.
c.
a homogeneous, molecular mixture of two or more substances.

Its easier for kids to understand that the salt disappears in the water but doesn’t go away. This is a good time to revisit the earlier observations of the water and salt before they were combined and discuss what’s changed. (Ex: the water is no longer clear, but cloudy, it tastes salty, its possibly more difficult to stir, it might smell bad, etc.)

NEXT: tie each end of the string (oh, and you only need about six inches of string – I had way too much) around your chosen weight (in my case it was screws) and drop one end into each cup so they’re connected.

Now that you have two cups of salt water connected by a string bridge it’s interesting to ponder what might happen. Also known as forming the hypothesis.

Young scientists might have trouble forming a hypothesis at the beginning of an experiment, or understanding what hypothesis means. Sometimes the picture becomes more clear once everything is set up and the concept of hypothesis is easier to explain after its happened.
Some possibilities to guide your scientists to consider are, do they think the string will absorb the water? What about the salt? What does evaporation mean? Will salt evaporate or just the water? And so on. Also take a minute to sit and watch the string. Is anything happening? No? Hmmm… Maybe tomorrow, then. Find an out of the way spot to put your experiment and check back 12-24hrs later.

And here’s what you can expect to happen after about 24 hours – salt crystals are beginning to form along the string where it laps over the edge of the cup. Given enough time and water and salt, there might begin to form in the center of the string salt stalagmites and stalactites. We did not pursue those formations in this experiment. Instead we were satisfied to see the salt was carried up the string by the water and then left behind when the water evaporated. Other things to notice at this point, the string is now stiff and crunchy, not soft and bendy as in the beginning. If kids are curious as to what the crystals are, suggest they give them a little lick. It will become obvious quickly that it is indeed salt!

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