What Factors Affect the Growth of
Crystals?
The story so far:
In science class we have been designing and conducting experiments to see what factors affect the growth of crystals. For our first experiment we all set up the same test conditions:
Solute: 2 Tbsp of salt.
Solvent: 6 oz. tap water, around 15-20 degrees Celsius
Wick: 30 cm of 1/4" cotton clothesline, wet.
We poured the saltwater into two 3oz. cups. We put each end of the clothsline into the cups and bent the clothesline in the middle. We set the experiment on a plastic plate and waited for about one week. This is more or less what we all saw:
Yair made these crystals.
These crystals are beautiful, Yair. Thank you for sending us this photo. Sure would like to know how you made these. Will you tell us?
David has done a follow-up crystal-growing experiment. He braided 3 strings together for his wick, and he sent in a report showing his results. After recording his observations, David concluded that "the more salt I put in the solute, the better the crystals grow." Do you agree with David's conclusion? Read his report and then let us know what you think. (I also think David's observation that "the largest crystals are at endings of the string" is interesting. Has anyone else discovered this?)
Jonah did a follow-up experiment at home. He didn't have any clothesline at home, so he used kitchen twine instead. And he used baking soda instead of salt for the solute. Here are his results:
Here is a close-up of the crystals that formed so far:
Those are really beautiful crystals, Jonah. Nice work. Comments, anyone? Anyone notice any differences from the crystals you grew in class?
Elliot sent in a photo of his home experiment.
Looks like he's got some nice crystals started.
I guess nowadays most people don't have clothesline at home. (We do, but my wife is from Indiana. That probably explains why.) I am interested in learning what people are using instead of clothesline.
Let me know about any substitutes for clothesline that you have tried.
You can also take 3 or 4 pieces of string and twist them together. Has anyone tired that?
A parent asked for an explanation of why the crystals form. Here is a brief explanation.
Here is an interesting video that explains why different crystals have different shapes.
Is anyone else doing a follow-up experiment at home? If you are, be sure to send photos of your results to gsimonelli@leffellschool.org and I will post them on our Homemade Crystals photo gallery!
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