MadSci Network: Chemistry

Re: What state of Matter is toothpaste?

Date: Fri Mar 9 02:47:21 2001
Posted By: Werner Sieber, Research Scientist, Colors Division, Ciba Specialty Chemicals Corp.
Area of science: Chemistry
ID: 983746913.Ch

Dear Mrs. Reno,

Toothpaste may look uniform to the unaided eye. But if you take a small 
sample of it, spread it in a thin layer, and look at it under a good 
microscope, you will see at least two components: roundish opaque 
PARTICLES distributed (DISPERSED) in transparent medium. Toothpaste is a 
special type of mixture called DISPERSION. The particles are solid, mostly 
calcium carbonate. The medium in between the particles is a COLLOIDAL 
solution of a POLYMER in water (like glue). This prevents the particles 
from settling out of the mixture, and gives the mixture its characteristic 
pasty consistence. 
In the case of such mixtures, you cannot strictly speak of "state of 
matter", since you have liquid and solid components side by side. 
COLLOIDAL refers to a type of distribution rather than a state of matter. 
Systems like toothpaste are not stable forever: If you left it undisturbed 
and well closed for centuries, the particles would grow to big chunks.

"PLASMA" has at least 3 scientific meanings (we shall not go into 
esoterics here)(source: ROEMPP Lexikon Chemie on CD, V.2): Blood plasma is 
the medium surrounding the blood corpuscles (leucocytes, erythrocytes 
etc). Cell plasma (cytoplasma) is what's inside the cells besides the 
nucleus. Both got their names well before their detailed nature was 
explored. The root of the word is the same as for "plastic". In physics, 
PLASMA was also assigned to something not very well known: the highly 
energetic state of matter where atoms are ionized and electrons are 
flitting about restlessly... Plasmas are created starting from gases e.g. 
in the process of arc welding.
Best Regards
Werner Sieber

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