Page 37 - Curriculum Visions Dynamic Book

 Polytetrafluoroethene coatings are found on many household pans to give them their nonstick finish.
The only problem with the material is that it is soft and so can be scratched with metal implements. For this reason wooden or plastic implements need to be used with nonstick pans.
corrosive: a substance, either an acid or an alkali, that rapidly attacks a wide range of other substances.
flux: a material used to make it easier for a liquid to flow. A flux dissolves metal oxides and so prevents a metal from oxidising while being heated.
polymer: a compound that is made of long chains by combining molecules (called monomers) as repeating units. (“Poly” means many, “mer” means part).
resin: natural or synthetic polymers that can be moulded into solid objects or spun into thread.
Fluoride and teeth
One of the most remarkable uses of a chemical has been the widespread use of compounds of fluorine in drinking water and toothpaste.
Teeth have a natural coating called enamel, made of calcium phosphate. This is quite a durable substance; however, tooth decay from eating too much sugar has become a serious problem in many countries.
Fluorides occur naturally in many water supplies, and scientists in the United States were able to show that in areas where there was more fluoride in the natural drinking water, there was a lower incidence of tooth decay. This is because fluoride strengthens the tooth enamel, creating a complex of calcium, fluoride and phosphate ions.
Fluoride is now added to many water supplies. However, too high a level of fluoride in the water may cause teeth to become very hard and brittle and to develop a dark brown colour. As a result it is important to control the level to about one part per million.
 Chains of units like the one shown above form solid polytetrafluoroethene. The fluorine atoms shield the carbon atoms that make the chain (polymer). Thus the carbon atoms form a polymer that is shielded from reaction by the fluorine: the secret of the material’s nonstick success.
Also...
Fluorine is corrosive enough to be one of
the few chemicals to react with diamond. In fact, fluorine is so reactive that it can actually extract oxygen from water. If fluorine gas is bubbled through water, the fluorine takes the hydrogen atoms from the water molecules to make hydrogen fluoride, or hydrofluoric acid, the world’s most corrosive and dangerous gas. At the same time it releases oxygen as a gas.
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