Posted on 13th November 2007 by Judy Breck in history | sciences
beans, beer, chemistry, chocolate, cocoa, history, MIT
This tasty learn node includes reports of discoveries in the history of chocolate from the Los Angeles Times, New York Science Times and other open sources relaying to the public science news that is from a source is limited to its paid subscribers (in this case the Proceedings of the National Academy of Sciences).
The chocolate news from the LA Times report:
Humans began exploiting cacao beans for alcohol before they started using them to make chocolate, according to new findings that push the earliest known use of cacao back about 500 years.
Residue scraped from pottery vessels dating to 1400 B.C. to 1100 B.C. indicate that residents of Honduras’ remote Ulua Valley fermented the sweet pulp of the chocolate plant to make an alcoholic drink well before they began grinding the bitter seeds and mixing them with honey and chiles to produce the equivalent of modern cocoa. . . .
Open chocolate history, chemistry and food information are richly available online. To pick a few pieces out of the virtual chocolate knowledge box: This MIT Kitchen Chemistry page includes a topic-by-topic online chocolate topic tour. Chicago’s Field Museum has an online chocolate knowledge feast Chocolate: The Exhibition. And the US Food and Drug Administration has a page (from which the image of chocolates above is taken) on its standards for chocolate.
More learn nodes at: learnodes.com
Posted on 1st September 2007 by Judy Breck in chemistry | engineering | general science
chemistry, materials, mixture, science, solution
The sketch in this learn node is from a course taught at MIT. You can virtually sit in on the lectures from the course by clicking this link: Fundamental Concepts of Material Science. The above sketch is from page 7 of lecture L2 PDF that you can download from the list you will get when you click the link. The sketch teaches us:
Mixture: Inhomogeneous multi-phase system where the components are not mixed on a molecular level.
Solution: Homogeneous system, components are mixed on a molecular level.
The difference between a solution and a mixture is a basic idea that the illustration above gives us � so that we can go on in our own learning to other concepts linked to the subject. The PDF of the lecture is an excellent place to move on in this learning; it has 13 pages of basics. The elemental new power of learning in the network ecology online is a matter of grasping a node like this one about “mixture or solution” and linking to related nodes to build concepts and experience thinking.
MORE LEARN NODES about mixtures and solutions from Rice University: “The word mixture can be defined as a heterogeneous association of substances that cannot be represented by a single chemical formula. This definition does not limit mixtures to solids mixed with liquids, nor is every mixture considered to be a solution. . . .”
More learn nodes at: learnodes.com
