This activity can be found in the January 2011 issue of the Journal of Chemical Education — “The science of chocolate: Interactive activities on phase transitions, emulsification, and nucleation” (pages 29-33). The article describes a presentation for children ages 6 and up, with specific activities categorized into grades K-4, 5-8 and 9-12. The five-page JCE article explains the science of the chocolate taste experiments and how to engage students in a discussion of some underlying chemistry concepts.
The following summarises the taste experiments into “question, test, answer and concept”.
- Question: Why does chocolate usually melt in your mouth, not in your hand? Which chocolate melts first in your mouth?
Test: Dark chocolate versus milk chocolate chips
Answer: Melting temperature depends on the material composition and the shape of the fat molecules.
Concept: Phase of matter; lipids composition
- Question: Why does chocolate feel smooth?
Test: European-style chocolate versus Mexican-style chocolate
Answer: Texture depends on particle size. Emulsifiers also help chocolate feel smooth.
- Question: Why does chocolate snap when you break it, and have sheen?
Test: Tempered (controlled crystallization) versus untempered chocolate (improperly stored)
Answer: Cocoa butter molecules need to pack in the right way or the chocolate becomes crumbly and spotty.
Concept: Phase transition; crystallization.
This worthwhile activity covers concepts such as phases of matter, phase transitions, lipid composition, particle size, amphiphilic molecules, emulsifiers, hydrophobic, hydrophilic, crystallization and nucleation. And it sounds like tremendous fun with materials readily available on Valentine’s Day.
For the complete article go to cambridgechocolate (PDF) or the JCE website, January 2011 issue (for access to the JCE posting, you will need to be a JCE subscriber)