The Effect of Temperature on Crystal Size

By Lalita Sundarrajan

Purpose

•The purpose of my experiment is to find out which brand of borax in which type of environment will produce the biggest, whitest, purest crystals.

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Hypothesis

•I hypothesize that the generic brand of Borax in the refrigerator environment will produce the best crystals.

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Research

•Crystallization is usually the last process chemists use to purify their ingredients when making a new product. This process can be done naturally or artificially. You can see crystallization in action whenever it is snowing outside because the water droplets in the clouds are changing into snow particles, which is a form of crystallization. When crystallization occurs, there are two main steps-nucleation and crystal growth. Nucleation is when the solute (solid) molecules dispersed in the solvent (liquid) start to cluster into groups, but only if they are clustering in ideal conditions. If not, then the clusters just re-dissolve.

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Research cont.

•Crystal growth occurs after the clusters have reached a certain size and cannot re-dissolve. Crystal growth is exactly what the name says, the process where the clusters grow bigger in size until they are big enough to be considered actual crystals. Crystals can be formed into different shapes and sizes, which is known as polymorphism.

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Materials

•1. Borax

•2. 3 jars (or other type of glass container)

•3. Aluminum foil

•4. Paper

•5. 3 Pencils

•6. Labels

•7. Balance

•8. Ice

•9. Water

•10. Heat source (preferably a stove)

•11. Thermometer

•12. String

•13. Scissors

•14. Clock or timer

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Procedures

•1. Put 30 g of Borax into each jar.

•2. Boil water and pour 35 mL of water into each jar.

•3. Stir water until Borax dissolves

•4. Wrap jars in aluminum foil

•5. Cut 3 pieces of string

•6. Attach each piece of string to a pencil.

•7. Place a pencil on top of each jar

•8. Put one jar in the fridge, one jar in an ice bath and one jar on a flat surface

•9. Wait 4 hours and observe the jars

•10. Record results.

Special Steps

•In order to avoid miscalculations, I made sure I used proper measuring techniques and used exact measurements. I also wrote down all the details that pertained to my experiment, even though they might have seemed minor or irrelevant.

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Independent Variables

• Type of Borax

• Temperature

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Dependent Variables

• Percentage of Yield

•Amount of Crystals

•Type of Crystals

•Weight of Crystals

•Size of Crystals

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Data Table

Data cont.

•Temperature of beaker environment

•Mass of Borax powder before crystallization

•Measurement of crystals after crystallization

•Trial 1 Borax was the Dial Boraxo Heavy-Duty brand

•Trial 2 Borax was the Dial 20 Mule Team brand

•Trial 3 Borax was the generic Wal-Mart brand

•Percentage Yield total overall for Beaker A is 19.73%

•Percentage Yield total overall for Beaker B is 18.34%

•Percentage Yield total overall for Beaker C is 20.28%

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Observations

•I observed the formation of my crystals by periodically looking at each beaker every one hour. I noticed that for the first hour, there was no change in any beaker of any kind. Then as I checked the second hour, I noticed that both Beaker B and Beaker C had started crystallizing. The solution in the beakers had developed this thin layer of what looked like ice and under that layer, you could still see the borax solution. During the third hour, all three beakers were undergoing crystallization and it appeared that Beaker B finished crystallizing first, because most of the solution was gone and in its place were these shiny, white, powdery looking crystals. By the time the fourth hour was up, all of the beakers had finished crystallizing.

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Observations cont.

•The crystals that had formed looked very white and they looked like they had little diamonds in them because they shone every time the light caught the crystals. In the beaker, you could see remnants of the solution because there were a few Borax powder grains. Also visible was the original “water level” of the solution because this white, chalky looking line was in the place of where the solution would have been. The crystals for the most part were also pretty sturdy and didn’t seem like they would break easily.

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Conclusion

•My experiment supported my original hypothesis that the generic brand of Borax in a cold temperature environment will yield the biggest and purest crystal as the highest percentage of yield came from the generic Borax and the crystals produced by the generic Borax in the cold temperature environment had the biggest crystals.

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Conclusion cont.

•I could probably improve my experiment by doing more trials, as I did only three. I could also use different types of Borax with different ingredients and from different stores since the Borax I used came from Wal-Mart and I only used three types of Borax for my experiment.

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Conclusion cont.

•Nothing unexpected occurred during my experiment. Everything went as planned and there were no unusual results or reactions while the experiment took place. It was a very precise, and controlled procedure.

•I think a follow up experiment could be to see what components make up a naturally formed crystal and compare artificial crystals to natural crystals. It would be interesting to see if the two share any common "ingredients" and find the similarities and differences of the two.

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Resources

•My mother

•Websites Used

http://www.novasep.com/technologies/Crystallization.asp

http://www.cheresources.com/content/articles/separation-technology/crystallization

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Aknowledgements

•I would like to thank my family for helping me find time to complete my project and being supportive of me and encouraging me to get a head start on it that way I wouldn't fall behind schedule. I would also like to especially thank my mother because she helped me understand some words I encountered while researching my project and clarified any doubts that I had, due to the fact that she teaches chemistry, and helped me find the materials needed for my project.

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Pictures