Fun with M & M's

This would be a great activity to use with students for the 2014 National Chemistry Week theme of candy. I wondered what would happen if the candy pieces, after dissolving a portion of the coating, were transferred to another container and water added again to continue the dissolving process. If there is an outer wax coating that's causing it, perhaps after it's largely gone, the effects would change. Students could ask so many questions about this—a good system to investigate further. A great opportunity for experimental design.

Interesting idea with the isopropyl alcohol—nice that it's an easy consumer chemical.

The 2013 NCW theme is energy, which ties in really nicely with your "And the Oscar Goes to...a Chemist!" JCE Classroom Activity and the hot dog demo. ACS keeps the NCW themes updated at http://www.acs.org/content/acs/en/education/outreach/ncw.html. There's a link on the page for future "NCW Dates and Themes." 2015 is color chemistry.

This is really neat!  It brings a couple questions to mind:

1) Are the coloring additives truly being dissolved? Or, is the mixture of coloring molecules applied as an emulsion or a colloid of some sort and it is actually bits of that emulsion/colloid that are being "dissolved" by the water solvent? If this were the case, it could be possible that the larger particles would rather not mix and would "bounce off" each other rather than mix together. One additive that could have caused this effect to disappear could have been soap which might be a strong enough surfactant to make everything mix. Emulsions are a common annoyance in working up many reactions and can often be combatted by increasing the ionic strength via addition of a brine solution. It could be interesting to see what happens upon addition of brine.  I keep going back and forth in my head with the logic of whether brine should make them mix better or worse... 

2) What happens to the coloring when the pH of the solution is changed?  Some of the coloring molecules are very similar to pH indicators.  It would be neat to change the color by causing a reaction.

3) Also, what is the time frame for these colors to remain separated? Is it indefinitely?  That time-frame may give some clues as to the type of particles that are mixing.

Interested to hear your thoughts!

Ben

I've been noodling around with this experiment this week, preparing some NCW materials for the ChemClubs. I hope to put together a video (with my limited equipment) of some of the things I did and write a post about it. I noticed today that the Steve Spangler link now has its carnauba explanation deleted. Interesting.

Thanks for the post and the comments to get my brain thinking!

I've got a grade 10 introductory class that is just starting to discuss solutions. So we're going to try some inquiry tomorrow and see what happens. I'm sure we'll be taking some pictures and/or video, which I'll be sure to share. My hope is to have the students develop research questions, which we can then turn into experimental designs for further testing.

I'll keep you posted.

Lowell

Erica's  experiment triggered an idea. Williams idea may confirm.

Obviously there is a density gradient issue as the materials from the third candy imediately went to the bottom of the beaker. What would happen if the experiment was performed in a large centrifuge tube. Revove the hard candies once the dyes and obviously initial sugars are dissolved into the water. Now centrigufe the results.

Why? 

Water stratification occurs when water masses with different properties  form layers that act as barriers to water mixing . These layers are normally arranged according to density, with the least dense water masses sitting above the more dense layers.Would Differential centrifugation be able to seperate the different dyes? Is it Water stratification that creates the barrier.?

This experiment was presented in backyard science episode 53- starting at 5:50

http://www.youtube.com/watch?v=NAGdaefU6gk&index=41&list=PLqmvix-jZkhN6C...

No. the high density frontline expansion model can't explain the direct mixing without introducing supplementary hypotheses.

One is that for some reason the blue color diffuses more than the brown one, maybe because of its smaller size.

In this case an invisible sugar frontline precedes the color frontline in the approach of blue to brown and of brown to brown,

but not in approaching the two blues, if the blue color diffusion has had enough time (if the two blue M&Ms are enough far away from each other).

Therefore, in the adapted model, you should find the nonmixing effect by putting the two blue M&Ms closer from each other,

or you could as well observe direct mixing by putting the two brown M&Ms far off.

In general, I tried in the past experiments attempting diffusive motion of different size anions and cations that were supposed to meet in some place along the connecting line forming some precipitate or coloured reaction. The outcome was flawed by the density layer effect.  Only by using a liquid with the same density of the two salt solutions you could testify something that could be correlated to the different ion sizes. I learned from the experiments (unfinished) and from calculations that the diffusion proper is not measurable in normal lab class times, because you would need several hours to observe pure diffusive motion of some centimeters in iso-density conditions.

However I'm really more interested in such experiments that try to eliminate the excess of useless variables and driving phenomena, so that a single theoretical source of explanation can be isolated. 

Furthermore, in my view, a real submicroscopical motion, as the diffusive motion of invisible and neutral hydrated ion clusters of different sizes, in a perfectly still and homogeneous liquid, that gives a final macroscopic and visible result that fits some atomic concept, is more interesting than some multiphenomenal coloured candies that serves to capture the curiosity at the beginning, but drives  quicly your students in a mess of magic and fantasy uncheckable pseudo-explanations.

Adolescent students already have an excess of fantasy, but poverty of construction of coherent links between claims, warrants, and data, and this is NOT, or not only because of incomplete knowledge of theories or experience, but also for the limited capacity of elaboration of thought in cases of multiple information, and for limited mastery of attention and voluntary memory. One of the reasons to attend school classes is to help them modifying and developing their high order thinking skills. In this case, it is better if they have only a very few theoretical abstract models, or only one at once, and if the experiment complexity is reduced in advance, because what matters more is that they discover their very limited explanation mechanism engine working well. After that you can add some more variable and complexity.

By following the path of direct complexity and fantasy you give only the illuson that everything's allright and no evolution of thinking skill is demanded: everyone lives in a aethernal brainstorming in which every utterance is good as every other.