Science Buddies: "Ask an Expert"

Hello,

I am doing the following experiment with my 5th grade daughter https://www.sciencebuddies.org/science- ... ml#summary

We have tried a couple time and can't seem to get any results so don't know where we are going wrong?

A couple of questions in general are: 1) Should the crystals be visible with the naked eye and if not will a 2x magnifying glass be enough to see them?
2) The maple syrup we found is dark amber grade a 100% pure. Is the dark color preventing us from observing crystal growth?
3) How big does the dollop have to be for best results (we used one that flattened out to about the size of a quarter)?
4) Expected the crystal growth to happen rather quickly (few seconds versus minutes) Is this assumption accurate usually?

Would appreciate a some thoughts or a push in the right direction. We have a couple weeks before this is due but don't want to be doing it last minute.

Thank you for your help and knowledge

Hi timd,

I'm sorry to hear you're having trouble with this project; crystal growing projects can be finicky. They often take a few tries before you get nice results because there are a lot of variables that can affect crystal growth.

Based on the underlying chemistry, the syrup will probably need to be reduced quite a bit. Be sure to keep stirring the syrup after it starts to boil, until the reduced syrup is very thick. How thick was the syrup you used after boiling it? (e.g., like honey? molasses? peanut butter?) If you boil the syrup for too long, you may get crystals forming even before you drop the syrup onto the ice. You're aiming for cooking the syrup until crystals are just about to form. You could do a little test to see how long you have to boil the syrup until you get crystals in the pan. Then, boil the syrup for a little bit shorter than that time when you do the actual project. The timing of how long you should boil the syrup is a bit of a Goldilocks problem, and it will vary from syrup to syrup, since there is a fair amount of variability in syrup composition.

Regarding your specific questions:

1) Sugar crystals are usually large enough to be seen by the naked eye, but a magnifying glass would definitely help.
2) It's possible the dark color might make it harder to see the crystals, but I don't think it would block you from seeing them entirely. You could try using a lighter colored syrup and see if that helps.
3) It might help to use somewhat larger dollops, perhaps using ~1 tablespoon of syrup per dollop
4) The crystals will probably take minutes, not seconds to form. The syrup has to cool sufficiently before the crystals begin to grow, so I wouldn't consider the experiment "over" until the syrup reaches ~room temperature. That will happen more quickly for the dollop on ice.

Let us know if you still have problems, and we'll see what else we can come up with.