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