Science Buddies: "Ask an Expert"

My daughter is growing rock candy for her science experiment and her question is whether seeding the string affects the growth rate of rock candy sugar crystals. We started the experiment 5 days ago and to this point the seeded strings have seen significant crystal growth but the non-seeded strings have seen none. Is this OK? IT proves our hypothesis that seeding does increase the growth rate, but I know some crystals should have grown on the non seeded strings. Should we let the crystals keep growing for an additional week; should we just conclude the experiment as is; or should we repeat the experiment as we may not have saturated the sugar solutions enough? Please help!

Hi Amy,

You have proven your hypothesis, so this project is complete. However, I would recommend growing the crystals for another week to give the non-seeded strings a chance to start growing and to grow the seeded crystals to a larger size that you can display at the science fair.

Science-wise, it's always better to repeat an experiment to verify that results are valid. However, for a very young student you would not need to do this. If the project is going to be entered into a science fair for judging, a project where the experiment has been repeated will score higher than an equivalent project with only one experiment.

Donna Hardy

Hello Amy,

I agree with Donna. I feel that if you persue what she has said your project will be great.
Best of Luck!

Thanks for your responses. We did do the experiment 3 times (all beginning on the same day) and no crystals grew on any of the strings that were not seeded. I think we will just let them grow for a few more days and then if there is no growth we may do some research and note some possible reasons (soluntion not saturated enough, string was too smooth, temperature, etc.) in the analysis and conclusion.

Hi Amy,

You did your experiment in triplicate, and obtained identical results with each trial. Fantastic! Great project.

If the you used the same sugar solution for both types of strings, then the solution is saturated. As the water evaporates, the non-seeded string containers will develop crystals. However, it may occur on the bottom of the container, not on the string.

Donna Hardy