|MadSci Network: Chemistry|
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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