Better Things for Better Living (part-1)

By: Dr.Badruddin Khan

In fact all matter on Earth is made of chemical substances and every material thing is a chemical or a mixture of chemicals. Our home is a virtual chemistry laboratory of fascinating products derived from raw materials such as the water, soil, rock, etc found in the biosphere of our planet. If we just scratch the surface of all the hundreds of chemical substances used in every home, it will open our eyes to the importance of chemical synthesis, engineering, manufacturing, and distribution of the substances used in our everyday life. Our homes, apartments, schools, offices, parks, rails, cars, buses, airplanes and subways all these are our' home' at one time or another as these are all just small parts of the home that we all share of our one, real home, the "Spaceship Earth" and through our study of chemistry, together we appreciate how that one precious home is truly a "World of Chemistry, a World of Choices".

Wood is mostly cellulose with the smaller amounts of hemicelluloses and lignin. All of these compounds are synthesized to be the structural parts of trees and are made via photosynthesis from carbon dioxide and water. Cellulose is simply glucose molecules linked together in the beta form to make long-chain molecules. Hemi cellulose differs from cellulose in that the sugar molecules of which it is composed contain only five carbon atoms rather than six, the missing carbon atom being the one that is not part of the six membered rings. Lignin is very different; it is a polymer of several aromatic alcohols such as conifer alcohol and vanillin.

Glass is an amorphous mixture of the oxides of Silicon (SiO2), Calcium oxide (CaO) and sodium oxide (Na2O). We know that mixtures are not compounds because the composition of a mixture is not fixed, but rather can vary over wide ranges. White sand is nearly pure SiO2 and is used directly in glass manufacturing whereas sodium and calcium oxides are formed by heating sodium carbonate and calcium carbonate, respectively

Na2CO3 ????????????????????????? Na2O + CO2

CaCO3??????????????????????????? CaO + CO2

These ingredients are heated together until they all melt and dissolve together. The mixture is then cooled slowly until the glass stiffens, it does not crystallize, so it is often spoken of as a super-cooled liquid rather than as a solid. In ordinary window glass, the mole ratio of the oxides is about 1.6 moles of Na2O to 1.0 moles of CaO to 6 moles of SiO2. Glass for other purposes utilize different ratios and often include other oxides. Well-known examples are Pyrex glass, which includes 12.5% boron-oxide; lead crystal, which contains typically 16% PbO: and stained glass, which contains various elements selected from the transition elements from Ti to Cu, depending on the desired color.

?Though nails aren't very high-tech materials, we all know how necessary they are not only for successful constructions bur also a number of purposes. Most nails are made of steel, which is an alloy containing mostly iron and carbon. Nails that are never expected to be in contact with water are plain steel, but nails used in installing shingles or external panels must be made resistant to rust. To prevent their rusting, steel nails are often galvanized. This means that they are coated with zinc, a good reducing agent so that rather than the iron being oxidized, the zinc will oxidize and the steel will not rust. Since zinc melts at a temperature (4190C) much below the melting point of iron (15350C), steel nails can simply be dipped into molten zinc, removed, and cooled.

Another option for rustles nails is to use aluminum instead of steel. There is a crucial difference between the products formed when iron and aluminum react with oxygen. While iron forms the characteristic red rust, Fe2O3, which flakes off and allows more iron to contact the air, aluminum also forms its oxide, Al2O3, but this oxide adheres tightly to the metal and prevents oxygen from reaching the rest of the metal. Aluminum is not as strong as steel so is seldom used for structural purposes. However, besides being light weight, it is valuable for adding to decoration.

People often speak of cement and concrete as if they were the same thing, but they are actually different substances. Concrete is the substance we drive on and it is made from cement, sand or gravel and water. The mixing of these three ingredients is done shortly before the wet concrete is put in place to harden. Cement on the other hand, is made by heating clay (typically Al2O3 .2SiO2. 2H2O) and limestone (CaCO3) until they begin to melt at about 12600C. This melt is called clinker and is then cooled and powdered to form what is sold commercially as Portland cement. Although cement is not a pure compound, a typical clinker compound is Ca3SiO5, which is more clearly written as 3CaO .SiO2.

We may believe it or not, even though concrete and cement have been used for millennia, there is still disagreement about what exactly happens when a mixture of sand, water, and Portland cement is allowed to set and harden. It is clear that the water reacts with CaO and Al2O3 to make Ca(OH)2 and Al(OH)3 which react with calcium silicates to form calcium aluminosilicate crystals, which interlock with each other. Concrete sets in a matter of hours and then continues to harden for years.

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