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Would this work for Scientific method?

Postby mom_w_qs » Wed Dec 31, 2014 11:33 am

Hello, My son is in 5th grade. He has to do a science fair project using scientific method. He wants to grow crystals using Ionized salt, Epsom salt and Sea salt. We planned to boil water and then add salt till dissolved, then add white vinegar, let cool then pour onto sponge and let set for several days. He wanted to compare the differences in the three types of salt crystals.
I think my son's idea for his project is great except I am not sure he can do it. He has to have a Control, Independent Variable and Dependent Variable. I think we need to change his idea to using only one type of salt and maybe different temperatures. Using the different temperatures we may also need to change to Borax instead of Vinegar. Any helpful ideas will help thank you so much.

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Re: Would this work for Scientific method?

Postby tdaly » Fri Jan 02, 2015 10:39 am

Hi mom_w_qs,

I think your son can probably do his experiment as-is. Sometimes it can be tricky identifying the different variables in a project, but your son's idea actually has independent, dependent, and controlled variables.

In the experiment your son wants to do, the independent variable would be the type of salt: iodized salt vs. Epsom salt vs. sea salt. The dependent variable (the thing that you observe or measure) would be the difference in the three types of salt crystal (size, shape, etc.). The controlled variables might include the concentration of each salt in the starting solutions, the place where the crystallizing solutions are kept, the type of container used to hold the solutions, and how long you allow the crystals to grow.

As an aside, part of why this should work is that while sea salt and iodized salt are both primarily sodium chloride, Epsom salt is a completely different chemical compound (magnesium sulfate). So, even though all three of the substances your son wants to try are called "salt", he is actually testing two very different chemicals. He will probably see nice differences in the shape of the Epsom salt crystals compared to the other two salts.
All the best,

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Re: Would this work for Scientific method?

Postby connief » Sat Jan 03, 2015 6:29 pm

Hi there,

I completely agree with Terik Daly that your son should be able to do his experiment as is and the controlled, independent, and dependent variables are as Terik Daly stated. Other controlled variables also include the sponges on which you grow the crystals, the temperature at which you boil the salt/water, and the amount of vinegar you add. Here is a very useful page on the Science Buddies website that explains how to identify different variables in your experiments: ... evariables.

Let us know if you have anymore questions!


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