Growing sugar crystals

Ask questions about projects relating to: biology, biochemistry, genomics, microbiology, molecular biology, pharmacology/toxicology, zoology, human behavior, archeology, anthropology, political science, sociology, geology, environmental science, oceanography, seismology, weather, or atmosphere.

Moderators: MelissaB, kgudger, Ray Trent, Moderators

Growing sugar crystals

Postby sunfish123 » Sat Dec 27, 2008 8:04 pm

My son's experiment is studying the effect of evaporation on sugar crystal growth. The first attempt we clearly did not add enough sugar to the water, but the jar with the fan blowing on it clearly exhibited evaporation, as the water level was lower than the other jars. This time we saturated the water with sugar but now the jars have a crust forming on the top. Is that the crystals forming? Granted, the experiment has only been running for 30 hours, but there are no crystals growing on the string or rock candy tied to the end. There does appear to be some sugar sitting on the bottom of the jar. The crust on top of the water seems to be preventing any evaporation. Do we need to break up the crusty layer? It's on both the regular jar and the jar with the fan blowing on it. (His third jar is closed with the lid and I haven't opened it to see if a crusty layer has formed on that one or not.) Thanks for any suggestions.
sunfish123
 
Posts: 3
Joined: Sat Dec 27, 2008 7:46 pm
Occupation: Audiologist
Project Question: Does evaporation affect the rate of sugar crystal growth?
Project Due Date: 1/27/09
Project Status: I am conducting my experiment

Re: Growing sugar crystals

Postby adance » Sun Dec 28, 2008 9:07 am

I think it would be good to break up the crust, so your solution is exposed to air.
Amber Dance
Science Buddy
adance
Former Expert
 
Posts: 137
Joined: Tue Sep 18, 2007 5:06 pm
Occupation: science journalist
Project Question: n/a
Project Due Date: n/a
Project Status: Not applicable

Re: Growing sugar crystals

Postby donnahardy2 » Sun Dec 28, 2008 9:36 am

Hi Sunfish,

Crystals can form on specks of dust in the saturated solution, and once they start forming, they will continue to grow on any solid surface available. If there is sugar at the bottom on the container, it's possible that not all of the sugar dissolved before you started the experiment. The crust is composed of thousands of small crystals, and if it is solid, it will prevent further evaporation. If you break the crust, this will allow evaporation and formation of more crust, since this is the primary solid surface that is available for new crystal formation. Crystal growth on the rock candy and string will be very slow since the crust is available for new crystal formation.

I assume that the jar with the lid is your no-evaporation control jar. If the solution is saturated, the lid will prevent evaporation and no new sugar crystals should appear. If you heated the sugar solution before setting up the experiment, the sugar solution may be supersaturated and sugar will come out of solution rapidly if the container is disturbed.

Science fair projects are great because there are no "right" or "wrong" results. The experiment is underway, and your son has some results to present, even if the crystals did not form on the string or the rock candy. Your son just needs to understand the science and present the results as they happened.

However, since the project is not due until the end of January, you still have time to try again to grow a large crystal on the string, if your son is still interested in doing this. The key is to make a saturated solution that does not have any dust or other particles in solution. The only surface should be the string and piece of rock candy. The evaporation rate should be very slow and the container should be completely undisturbed. The best way to do this with kids is the set up the experiment, and put it away out of sight, and check it one time at the end of the experiment. It is very nice when you can get a large crystal formed.

I hope this helps.

Donna Hardy
donnahardy2
Expert
 
Posts: 2230
Joined: Mon Nov 14, 2005 12:45 pm

Re: Growing sugar crystals

Postby sunfish123 » Sun Dec 28, 2008 10:40 am

Thanks for your reply. How do we make a solution without any dust or any other particles in it? We did wash the jars and boil the water. The experiment is sitting in an undisturbed location. Obviously, dust can settle in the two jars that are open. I did open one of our closed jars and it does not have a crusty layer. How do we get crystals to form on the string and not on the surface? I feel like we have followed the directions to grow crystals very carefully. Should we break up the crusty layer each day? Thanks again.
sunfish123
 
Posts: 3
Joined: Sat Dec 27, 2008 7:46 pm
Occupation: Audiologist
Project Question: Does evaporation affect the rate of sugar crystal growth?
Project Due Date: 1/27/09
Project Status: I am conducting my experiment

Re: Growing sugar crystals

Postby donnahardy2 » Sun Dec 28, 2008 11:31 am

Hi Sunfish,

The particles that initiated the crystallization in your son's experiment were probably present in the sugar itself. I have not tried this, but you could try filtering the saturated sugar solution through a couple of layers of coffee filter to remove particles less than 5 microns that serve as nuclei for crystal formation. That would make the string and piece of rock candy the most available surface for the formation of new crystals. Buying pure sucrose from a scientific supply company would probably also work, but I don't recommend this option because it would be too expensive.

However, please don't be concerned about the results. I have done this and similar experiment with kids in the past, and the crystals that form are usually not on the string. The crust is the result of the formation of lots of individual crystals. If you break the crust every day, more crust will be able to form, but you won't ever get a large crystal formation on the string as long as the crust is present.


Donna Hardy
donnahardy2
Expert
 
Posts: 2230
Joined: Mon Nov 14, 2005 12:45 pm

Re: Growing sugar crystals

Postby dancingonli93 » Sun Dec 28, 2008 2:29 pm

Here's a method of growing crystals where you tie a string to a pencil or butter knife and the crystals form on the string:
http://chemistry.about.com/od/growingcr ... rystal.htm
dancingonli93
Former Expert
 
Posts: 8
Joined: Mon Nov 24, 2008 1:10 pm
Occupation: Student
Project Question: n/a
Project Due Date: n/a
Project Status: Not applicable

Re: Growing sugar crystals

Postby lrp » Tue Feb 15, 2011 11:01 am

My son is doing the rock candy experiment, we have not seen anything form on the string. there is a small crust that has formed on the top layer of the solution, that we have broken up everyday. the solution has not evaporated at all, is it possible that we made it too syrupy? It has been 4 days.
lrp
 
Posts: 2
Joined: Tue Feb 15, 2011 9:34 am
Occupation: homemaker
Project Question: my 9 year old son did the rock candy experiment, problem is there has been no activity. I believe we may have put to much sugar in the water, because it is like syrup....HELP!
Project Due Date: today is 02/15/2011 his project is due 02/18/2011
Project Status: I am conducting my experiment

Re: Growing sugar crystals

Postby donnahardy2 » Tue Feb 15, 2011 12:00 pm

Hi,

How did you make the saturated sugar solution? Crystals will not form if it is possible for more sugar to dissolve in the water. If you do have a saturated solution, then you need to wait until some of the water evaporates from the sample. Another possibility is that there is something else in the sample that interferes with crystallization, such as some lipid (fat or fingerprints).

Let us know if you don't see crystals in the near future.

Donna Hardy
donnahardy2
Expert
 
Posts: 2230
Joined: Mon Nov 14, 2005 12:45 pm

Re: Growing sugar crystals

Postby lrp » Wed Feb 16, 2011 10:13 am

We added 4 cups of sugar to 2 cups of boiling water, and then added four more tablespoons (one at a time) until the sugar would not dissolve anymore. We are using a 14 oz. jar, that we covered after we set up the experiment.
Thanks for your input!
lrp
 
Posts: 2
Joined: Tue Feb 15, 2011 9:34 am
Occupation: homemaker
Project Question: my 9 year old son did the rock candy experiment, problem is there has been no activity. I believe we may have put to much sugar in the water, because it is like syrup....HELP!
Project Due Date: today is 02/15/2011 his project is due 02/18/2011
Project Status: I am conducting my experiment

Re: Growing sugar crystals

Postby donnahardy2 » Wed Feb 16, 2011 5:15 pm

Hi,

It sounds like you made a saturated solution. Has the temperature changed since you made the solution? I recommend that you take the cover off and maybe add a fan in the background or some sort of gentle air circulation to encourage evaporation. The crystals will start to form as soon as some of the water evaporates.

Donna Hardy
donnahardy2
Expert
 
Posts: 2230
Joined: Mon Nov 14, 2005 12:45 pm

Re: Growing sugar crystals

Postby Mnmeyers » Thu Jan 19, 2012 12:48 am

Hi,

Is it possible to make the solution too syrupy? We had to create an extra amount of solution since our jars were bigger but we maintained the 1 water to 2 cup sugar ratio by doing 4 cups water 8 cups sugar. We followed the steps on boiling but the solution is thick like syrup. We haven't seen any crystals form on any string 2 days in just hardening on the top. Will the thickness of the solution allow the experiment to work?
Mnmeyers
 
Posts: 1
Joined: Thu Jan 19, 2012 12:41 am
Occupation: 5th grade student
Project Question: Rock candy crystals
Project Due Date: January 26th
Project Status: I am conducting my experiment

Re: Growing sugar crystals

Postby donnahardy2 » Sun Jan 22, 2012 9:05 am

Hi,

This is a great project. If the surface has hardened, then the sugar solution is probably concentrated enough, however, something is inhibiting the crystal formation.

Were you following the experiment described in the science buddies website?

http://www.sciencebuddies.org/science-f ... p005.shtml

The procedure includes some important details that are essential for the success of the experiment, including seeding the string with sugar crystals to provide a surface to form the crystals, checking to make sure all of the sugar is dissolved in the saturated solution, leaving the jars undisturbed during the experiment, avoiding large temperature fluctuations, loosely covering the containers to avoid dust and other particles. It’s also possible that you accidentally added oil or another contaminant that would interfere with crystallization during the preparation of the sugar solution.

Now, here is good news for you. I see your project is due this week and there’s not enough time to repeat the experiment before the deadline. I would not recommend setting up the experiment again, however, you should focus on preparing your project board, and final report if it is required. Getting the results that you expected is not essential for a successful science fair project, however, you will need to write up your results and demonstrate that you understand the scientific method and how to do a controlled science project. Here is the information from the Science Buddies website on preparing your project board:

http://www.sciencebuddies.org/science-f ... oard.shtml

You should make sure that you write up each section. State your purpose and hypothesis and include a detailed materials and procedure section. In your background section, include the science behind crystal formation. For your results, you will have to report that you did not observe crystal formation. A photograph of your results might be helpful since you don’t have anything to measure. Your conclusion will be very interesting, however, because you can go through the method from the Science Buddies experiment and discuss what might have gone wrong. Your analysis of the problem and statement of what you would do differently next time (if you had time) will help complete the project. Be sure to go back and read the written assignment from your teacher and make sure you include all required information.

You should not expect to win at the science fair, but you can still get an “A” on the assignment by demonstrating how much you know about science. Let me know if you have any questions. Good luck!


Donna Hardy
donnahardy2
Expert
 
Posts: 2230
Joined: Mon Nov 14, 2005 12:45 pm

Re: Growing sugar crystals

Postby bethm » Mon Jan 23, 2012 1:15 pm

Help. We tried the growing rock candy crystals for my daughter's science fair project and it didn't work. After 8 days crystals are only forming on the surface of the liquid and not on either string. We followed the project exactly. We're going to start over but need to complete the project by Feb. 15. Should the sugar solution be cooled longer than 5 min. before putting the strings in the solution? We cooled it 5 min. like the directions said but the sugar on the seeded string dissolved because the solution was so hot. Any suggestions would be helpful.
bethm
 
Posts: 2
Joined: Mon Jan 23, 2012 1:00 pm
Occupation: parent
Project Question: help with "When Science is Sweet: Growing Rock Candy Crystals"
Project Due Date: 2/15/12
Project Status: I am finished with my experiment and analyzing the data

Re: Growing sugar crystals

Postby donnahardy2 » Mon Jan 23, 2012 2:28 pm

Hi,

If the project is due February 15, then you have time to set it up again. If you think the solution was hot enough to dissolve the seed crystals after 5 minutes of cooling, then definitely let it cool a little longer. The sugar will crystallize on any solid surface, so there might have been some dust or impurities in the sugar solution itself that allowed crystallization to occur in the solution first rather than on the seeded string. Once crystallization starts, it continues at the same place.

However, I want to reassure you that your results are acceptable for a science fair project and you cannot say that your daughter’s project did not work. You have done your experiment and obtained crystallization on the surface of the saturated solution rather on the string. A scientist would say that your results are empirical, or what you actually observed. This means that you might not have confirmed your hypothesis, but the results are not wrong, just unexpected. For the science project, if you understand the science behind saturated solutions and crystallization and can explain why the crystals appeared on the surface rather than the string, then your project will be successful.

http://en.wikipedia.org/wiki/Empirical

Please do reread my post from yesterday and focus most of your time and energy into the presentation of the results. Since you do have time, I do recommend trying the experiment again, making sure the sugar solution is saturated and extending the initial cooling time to 10 minutes, and loosely covering the container so that surface is not disturbed, but if you get the same results again, please do not worry about it.

Let me know if you have other questions.

Donna Hardy
donnahardy2
Expert
 
Posts: 2230
Joined: Mon Nov 14, 2005 12:45 pm

Re: Growing sugar crystals

Postby bethm » Mon Jan 23, 2012 2:54 pm

Thank you. I should have mentioned that the sugar should have been saturated. Our jars were over 14 oz. so 2 c. of water and 4 c. of sugar. We added an additional 5 Tbsp. of sugar until the liquid was saturated. We also preheated the jars prior to adding the liquid so that may have caused them to be too hot as well. Should the sugar solution be room temperature before adding the strings? We did cover the jar with a paper towel to prevent dust from falling in the solution.
bethm
 
Posts: 2
Joined: Mon Jan 23, 2012 1:00 pm
Occupation: parent
Project Question: help with "When Science is Sweet: Growing Rock Candy Crystals"
Project Due Date: 2/15/12
Project Status: I am finished with my experiment and analyzing the data

Next

Return to Grades K-5: Life, Earth, and Social Sciences

Who is online

Users browsing this forum: Bing [Bot] and 3 guests