From: Marc Kossover (zeke_kossover@yahoo.com)
Date: Mon May 09 2005 - 07:23:11 PDT
Message-ID: <20050509142311.34082.qmail@web53401.mail.yahoo.com> Date: Mon, 9 May 2005 07:23:11 -0700 (PDT) From: Marc Kossover <zeke_kossover@yahoo.com> Subject: Re: fun chem labs
From: Marc Crown <mcrown@gatewayhigh.org>
Subject: fun chem labs
Date: Sun, 8 May 2005 14:20:39 -0700
> something that will send em off with a desire to
take
> more chemistry.
Do you have hot plates and some clean labwear or pots
and pans of your own? If so, the chemistry of cooking
can be a blast. I've taught this off and on to adults
and children for years.
The way to make this scientific, though, is to give
different recipes to the different groups in class and
have them compare the results after they are done.
That way they can see what's happening.
You might want to start with simple candies. You can,
for example, add water to granulated sugar (sucrose)
to make syrup and then evaporate the water back out
again to make sugar (sucrose) crystals. If you add a
10 mL of corn syrup (nearly pure fructose) to a 250 mL
of sucrose, it will never re-crystallize; however, and
brown into carmel. Why? The fructose is not the same
shape as sucrose and interfers with crystal formation.
That means that the water keeps evaporating until the
solution gets so hot that the sucrose starts to brown.
Serve over ice cream, which as another person has
pointed out has several bits of useful chemistry
involved. Not just freezing point depression necessary
to freeze the water, but kneading and aerating the
mixture to keep the crystals small the product less
dense.
Making fudge falls into the same crystallization
problem. Fudge is primarily sugar and fat with a bit
of chocolate (or other) flavoring. You want many small
sugar crystals to make the candy soft and creamy
feeling. Once everything is melted and combined, you
want to cool it gentle at first so that many crystals
are formed, then you want to beat it hard to keep the
crystals from growing. Fudge made with marshmallow
cream works because it includes fructose in the
marshmallow cream and stabilizers (like gelatin) to
hold the fudge together even without good crystals.
If you'd like more ideas, even ones that aren't candy,
just drop me a line.
Resources:
Cookwise: The Hows and Whys of Successful Cooking by
Shirley O. Corriher
On Food and Cooking: The Science and Lore of the
Kitchen by Harold McGee
<http://www.exploratorium.edu/cooking/index.html>
Marc "Zeke" Kossover
The Jewish Community High School of the Bay
San Francisco, CA 94121
<http://tochnit.jchsofthebay.org/~zkossover>
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