| In fact all matter on Earth is made of | | | | and stained glass, which contains various |
| chemical substances and every material thing | | | | elements selected from the transition |
| is a chemical or a mixture of chemicals. Our | | | | elements from Ti to Cu, depending on the |
| home is a virtual chemistry laboratory of | | | | desired color. |
| fascinating products derived from raw | | | | |
| materials such as the water, soil, rock, etc | | | | Â |
| found in the biosphere of our planet. If we | | | | |
| just scratch the surface of all the hundreds | | | | Â Though nails aren't very high-tech |
| of chemical substances used in every home, it | | | | materials, we all know how necessary they are |
| will open our eyes to the importance of | | | | not only for successful constructions bur |
| chemical synthesis, engineering, | | | | also a number of purposes. Most nails are |
| manufacturing, and distribution of the | | | | made of steel, which is an alloy containing |
| substances used in our everyday life. Our | | | | mostly iron and carbon. Nails that are never |
| homes, apartments, schools, offices, parks, | | | | expected to be in contact with water are |
| rails, cars, buses, airplanes and subways all | | | | plain steel, but nails used in installing |
| these are our' home' at one time or another | | | | shingles or external panels must be made |
| as these are all just small parts of the home | | | | resistant to rust. To prevent their rusting, |
| that we all share of our one, real home, the | | | | steel nails are often galvanized. This means |
| "Spaceship Earth" and through our study of | | | | that they are coated with zinc, a good |
| chemistry, together we appreciate how that | | | | reducing agent so that rather than the iron |
| one precious home is truly a "World of | | | | being oxidized, the zinc will oxidize and the |
| Chemistry, a World of Choices". | | | | steel will not rust. Since zinc melts at a |
| | | | temperature (4190C) much below the melting |
| Wood is mostly cellulose with the smaller | | | | point of iron (15350C), steel nails can |
| amounts of hemicelluloses and lignin. All of | | | | simply be dipped into molten zinc, removed, |
| these compounds are synthesized to be the | | | | and cooled. |
| structural parts of trees and are made via | | | | |
| photosynthesis from carbon dioxide and water. | | | | Another option for rustles nails is to use |
| Cellulose is simply glucose molecules linked | | | | aluminum instead of steel. There is a crucial |
| together in the beta form to make long-chain | | | | difference between the products formed when |
| molecules. Hemi cellulose differs from | | | | iron and aluminum react with oxygen. While |
| cellulose in that the sugar molecules of | | | | iron forms the characteristic red rust, |
| which it is composed contain only five carbon | | | | Fe2O3, which flakes off and allows more iron |
| atoms rather than six, the missing carbon | | | | to contact the air, aluminum also forms its |
| atom being the one that is not part of the | | | | oxide, Al2O3, but this oxide adheres tightly |
| six membered rings. Lignin is very different; | | | | to the metal and prevents oxygen from |
| it is a polymer of several aromatic alcohols | | | | reaching the rest of the metal. Aluminum is |
| such as conifer alcohol and vanillin. | | | | not as strong as steel so is seldom used for |
| | | | structural purposes. However, besides being |
| Glass is an amorphous mixture of the oxides | | | | light weight, it is valuable for adding to |
| of Silicon (SiO2), Calcium oxide (CaO) and | | | | decoration. |
| sodium oxide (Na2O). We know that mixtures | | | | |
| are not compounds because the composition of | | | | Â |
| a mixture is not fixed, but rather can vary | | | | |
| over wide ranges. White sand is nearly pure | | | | People often speak of cement and concrete as |
| SiO2 and is used directly in glass | | | | if they were the same thing, but they are |
| manufacturing whereas sodium and calcium | | | | actually different substances. Concrete is |
| oxides are formed by heating sodium carbonate | | | | the substance we drive on and it is made from |
| and calcium carbonate, respectively | | | | cement, sand or gravel and water. The mixing |
| | | | of these three ingredients is done shortly |
| Na2CO3 Â Â Â Â Â Â | | | | before the wet concrete is put in place to |
| Â Â Â Â Â Â Â | | | | harden. Cement on the other hand, is made by |
| Â Â Â Â Â Â Â | | | | heating clay (typically Al2O3 .2SiO2. 2H2O) |
| Â Â Â Â Â Na2O + CO2 | | | | and limestone (CaCO3) until they begin to |
| | | | melt at about 12600C. This melt is called |
| CaCO3Â Â Â Â Â Â | | | | clinker and is then cooled and powdered to |
| Â Â Â Â Â Â Â | | | | form what is sold commercially as Portland |
| Â Â Â Â Â Â Â | | | | cement. Although cement is not a pure |
| Â Â Â Â Â Â Â | | | | compound, a typical clinker compound is |
| CaO + CO2 | | | | Ca3SiO5, which is more clearly written as |
| | | | 3CaO .SiO2. |
| These ingredients are heated together until | | | | |
| they all melt and dissolve together. The | | | | We may believe it or not, even though |
| mixture is then cooled slowly until the glass | | | | concrete and cement have been used for |
| stiffens, it does not crystallize, so it is | | | | millennia, there is still disagreement about |
| often spoken of as a super-cooled liquid | | | | what exactly happens when a mixture of sand, |
| rather than as a solid. In ordinary window | | | | water, and Portland cement is allowed to set |
| glass, the mole ratio of the oxides is about | | | | and harden. It is clear that the water reacts |
| 1.6 moles of Na2O to 1.0 moles of CaO to 6 | | | | with CaO and Al2O3 to make Ca(OH)2 and |
| moles of SiO2. Glass for other purposes | | | | Al(OH)3 which react with calcium silicates to |
| utilize different ratios and often include | | | | form calcium aluminosilicate crystals, which |
| other oxides. Well-known examples are Pyrex | | | | interlock with each other. Concrete sets in a |
| glass, which includes 12.5% boron-oxide; lead | | | | matter of hours and then continues to harden |
| crystal, which contains typically 16% PbO: | | | | for years. |