Growing crystals (rock candy)

[Pbowens57]

Hoping someone can answer this question. I'm helping my grandson with his 5th grade science project which is growing crystals (Rock candy). He decided to see if the crystals would grow better on salt seeded or sugar seeded strings. We keep hearing how easy this project is, but honestly it has been a challenge. The first trial didn't grow much at all except on the jar. We increased the saturation of his solution and then the crystals grew like crazy, all over the sides and top and bottom of of the jar. We are going to move on to trials 3 and 4 now but I find myself wondering if it is even a possibility that the sugar crystals will grow on a salt seeded string. I was an accounting major in college so please excuse my scientific ignorance. But It would be nice to know if we're on the right track.
Also wondering if we're correct that the only independent variables are salt seeded or sugar seeded.
Thanks.

[donnahardy2]

Hi Pbowens57,

Welcome to Science Buddies! I think you are doing this excellent project:

https://www.sciencebuddies.org/science- ... p005.shtml

It sounds like there were some particles on the sides of the container that allowed the crystals to start growing on the container rather than on the string. And on the second trial, you may not have completely dissolved all of the sugar in the water.

For the next trial, make sure you start with perfectly clean containers and avoid getting fingerprints inside the jars. The saturated solution should be perfectly clear; if it is cloudy then continue heating or add a small amount of water back to dissolve all of the sugar. The sugar molecules can start forming crystals on particles of dust, so don't dry the containers with a paper towel or a cloth that should add particles; just dry by air.

Sugar and salt crystals have a different shape, so there might be a difference in the way the crystals start to form on the string. . Have your grandson look for any differences in the size of the crystals or in the time that it takes for crystals to start forming on the next experiment. Here are links that show the difference in the shape of sugar and salt crystals.

https://www.google.com/search?q=structu ... AdIQsAQIGw

https://www.google.com/search?q=structu ... AQwQsAQIIQ

Please let us know if you have any other questions.


Donna Hardy

[Pbowens57]

Thank you. I think you're probably correct that there could have been fingerprints or lint in the jar. I'm pretty sure the solution was "super saturated" but it was clear, so I think we're okay on that one.
We'll try again making sure we follow your suggestions.
And thanks so much for the diagrams and tips on the actual formation. We did notice the salt seeded had some really irregular forms. Something we really didn't think about.
Again thank you so much.

[donnahardy2]

Thanks for your reply. I hope my suggestions were helpful.

If the crystals don't form as expected in your next experiment, try a different brand of sugar. Sometimes sugar has microscopic particles that can form nuclei for crystals to start forming everywhere except on the string.

Also, please explain to your grandson that the science experiment was successful even if the results did not turn out as expected. One nice thing about science experiments is that there's no requirement for perfect results. The student does the carefully controlled experiment and records the results. If the results are unexpected, they should be explained in the discussion section. So your grandson might have a more interesting discussion section in his project, but he definitely has results to report.

Good luck!

Donna

[Pbowens57]

Donna, I wanted to thank you for your help and tell you that my grandson good third place for his science fair project.
We both appreciate your advice!
Thanks again for helping to make this an enjoyable experience for him!

[donnahardy2]

Hi,

Congratulations to your grandson for the science fair award! I hope that the overall experience was positive so he will be looking forward to doing another project next year.

Thanks so much for letting me know about the science fair judging. You should also get an award for your perseverance and support in helping him get the project done.


Donna