Cheryl L Litman on wed 17 dec 97
Question number 1: I was hoping one of the chemists on the list could
tell me the main differences between "solutions" and "colloids" -
application-wise that is. I'm teaching 7/8th grade science and the text
has a lab where we test for the "Tyndall effect". We're using things
like sugar, salt, alcohol, milk, tea, etc. in water for the lab.
According to the book if you see a beam of light in the test tube it's a
colloid (larger particles scattering the light) and if you don't see the
beam of light it's a true solution. A couple of kids are basically
asking "who the hell cares" and I'm somewhat at a loss to explain why
they should know this tidbit. I know that colloids can be coagulated with
changes in temperature, ph... but is there some relevant info/reason to
know that I could pass on to them?
Question number two: I'm working with a group called Science Alliance
which is an industry and education partnership. I want to develop a
series of activities on growing crystals, something for the K-6 age
range. I would like an industry tie-in rather than just fooling around
growing salt, sugar and Epsom salt crystals. I know crystals are used in
electronics, lasers, manufacture of drugs... Any idea which type of
person/industry (or a who specifically) I should contact to find an
industry partner? Any good info out there that I can tap for background?
TIA
Cheryl Litman
Somerset, NJ
email: cheryllitman@juno.com
Talbott on thu 18 dec 97
The difference between true solutions and colloidial suspensions has to do
with the particle size of the solute. The particle size of the solution
being the smaller of the two.. I can't remember the solute sizes... Most
solids do form crystals and very few solids are amorphic... Diamonds are
crystals for example as are other gem stones.. Consult a friendly
neighborhood jeweler and ask him or her to visit you class and give a
talk/demo on gem stones... Marshall
>----------------------------Original message----------------------------
>Question number 1: I was hoping one of the chemists on the list could
>tell me the main differences between "solutions" and "colloids" -
>application-wise that is. I'm teaching 7/8th grade science and the text
>has a lab where we test for the "Tyndall effect". We're using things
>like sugar, salt, alcohol, milk, tea, etc. in water for the lab.
>According to the book if you see a beam of light in the test tube it's a
>colloid (larger particles scattering the light) and if you don't see the
>beam of light it's a true solution. A couple of kids are basically
>asking "who the hell cares" and I'm somewhat at a loss to explain why
>they should know this tidbit. I know that colloids can be coagulated with
>changes in temperature, ph... but is there some relevant info/reason to
>know that I could pass on to them?
>
>Question number two: I'm working with a group called Science Alliance
>which is an industry and education partnership. I want to develop a
>series of activities on growing crystals, something for the K-6 age
>range. I would like an industry tie-in rather than just fooling around
>growing salt, sugar and Epsom salt crystals. I know crystals are used in
>electronics, lasers, manufacture of drugs... Any idea which type of
>person/industry (or a who specifically) I should contact to find an
>industry partner? Any good info out there that I can tap for background?
>
>TIA
>Cheryl Litman
>Somerset, NJ
>email: cheryllitman@juno.com
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Tim Stowell on thu 18 dec 97
When in college my freshman year I had a professor..Egon
Macteyivich(sp?)..he scared the hell out of us..anyway at that time he
was one of the worlds leading experts on colloids. One of the major uses
of colloidal solutions that I remember was the application of non-stick
surfaces onto metals - teflon pans. However I beleive they use a plasma
technology now. Controlled precipitation can be used to apply extremely
smooth coatings.
The most visible use of colloids by the public was a product that I
believe is no longer available in the US---Jell-O 1,2,3. Remember the
stuff that separated into three layers.
Terra Sigilato is a colloid.
Tim
Tim Stowell Gerard Stowell Pottery
Stacey Gerard 290 River Street
tstwll@juno.com Troy, NY 12180
(518)272-0983
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