Chemistry is all around us. Everyone can and should understand basic chemistry. The Story Apart from those wanting to become chemists, students Central wanting to become doctors, nurses, physicists, Science Cover nutritionists, geologists, and pharmacists all need to study chemistry. It is important to remember that the Chemistry importance of chemistry would not be diminished BIMAN BASU over time; rather it will continue to remain a That is not all. There would be no drugs a science. It was primarily directed at efforts promising career prospect. – painkillers, antacids, or antibiotics – no to turn all kinds of substances into the polyester fibre or nylon stockings, no precious metal gold by early chemists, who stainless steel, no sugar-free soft drinks, were known as alchemists. We have heard IGHT from the moment we get up in even no Diwali illumination and fireworks about the “philosopher’s stone” using which the morning till we go to bed at without chemistry. Without chemistry, we the alchemists sought to turn any metal night, we come intimately close to R would not have such items as computers, into gold. Of course it was a silly thought, chemistry and things related to it. The CDs, DVDs, iPods, fuel for vehicles, oil to because no one can really turn one toothpaste we use to clean our teeth, the cook, refrigeration units, radios, televisions, element into another by mere touch! Still, toilet soap, shampoo, and plastic buckets batteries, and so much more. So, then, the alchemists made important we use to take bath, the plastic comb we what is chemistry? contributions to chemistry; they developed use to comb our hair, the melamine cups many of the techniques used by modern and plates we use at breakfast, the cooking gas our mother uses in the kitchen, Chemistry Around Us chemists like distillation, filtration, etc., and the iodised salt she uses to cook food, the In brief, we can say, chemistry is all about were also the first to use symbols for some ink in the pen we write with, the inks this the nature of all matter around us – air, common elements like gold and mercury. magazine is printed with, the beautiful dyes water, metals, plastics, drugs, everything – The real importance of chemistry that brighten up our dresses, the about how they behave, how they react, stems from the fact that it serves as a polyurethane foam mattress that makes and how they change. It is about changing common interface between practically all our sleep at night comfortable, and a host one kind of material into another. of the other sciences – medicine, biology, of other items of daily use are all products In fact, the practice of chemistry engineering, geology, and manufacturing of chemistry. started thousands of years ago, but not as – as well as between many other areas of Chemistry serves as a common interface between practically all of the other sciences Even fireworks are possible only because of chemistry SCIENCE REPORTER, APRIL 2011 88 CoverCoverCover Story There would be no drugs, stainless steel, sugar-free soft drinks, CDs, DVDs and iPods, televisions and a host of other things without chemistry Apart from those wanting to first published in 1977, with a 12th edition published in 2011.) become chemists, students This is not an overstatement, because wanting to become doctors, a student with a solid background in nurses, physicists, nutritionists, chemistry would find it far easier to migrate into other fields as his/her interest develops. geologists, and pharmacists all But, unfortunately, many science students chemical elements – the simplest need to study chemistry. find chemistry boring, and some find it a substances into which ordinary matter may human endeavour such as art and culture very hard subject to understand. But that be divided – and the way they react with where paints, colours, dyes and fabrics – need not be so. each other. As early as 1660, Irish-born all products of chemistry – play a key role. Chemistry is primarily concerned with chemist Robert Boyle recognised that the For this reason, chemistry is often called Greek definition of element (earth, fire, air, the “central science”. (The phrase was and water) was not correct. Boyle popularised in a textbook by Theodore L. proposed a new definition of an element Brown and H. Eugene LeMay titled as a fundamental substance, and we now Chemistry: The Central Science, which was define elements as fundamental John Dalton’s atomic theory could explain the facts of substances that cannot be broken down chemical combination as they were then known (below), further by chemical means. But Boyle did Various atoms and molecules as depicted in John Dalton’s not elaborate on the nature of the A New System of Chemical Philosophy (1808) (right) elements or compounds. The 118 chemical elements known today constitute the “alphabet” of matter because everything else is made of some combination of these. (Of course, many of the transuranium elements do not occur in nature; they are artificially produced.) The elements can combine by reacting together to form a multitude of compounds that make up everything in this universe, including us. Everything around us is formed by a combination of two or more of these elements. So, in order to understand chemistry one has to know about the chemical elements, about their properties, about how they react, and about why they react the way they do. But doing that is not as difficult a task as it may sound. It is possible 9 SCIENCE REPORTER, APRIL 2011 CoverCoverCover Story Friedrich Wohler overturned the vitalism theory by converting the inorganic salt ammonium cyanate into urea, which is an organic compound (right); Friedrich August Kekulé brought in a revolution in structural chemistry by suggesting a ring structure for benzene (extreme right) Dmitri Mendeleev was able to bring of chemical combination as they were that a chemical compound always a system of classifying the elements then known. The idea of atoms had been contains same elements combined that made their study easier proposed much earlier. The ancient Greek together in the same proportion by mass. philosophers had talked about atoms, but These were great achievements in to learn about the elements even without Dalton’s theory was different in that it was understanding how the chemical elements memorising complex equations and supported by careful chemical combine. All the three scientists formulated formulae. Of course, getting familiar with measurements. It was not just a their laws after careful and extensive the chemical symbols can be of great help philosophical statement. experimentation – an essential prerequisite in understanding the subject better, as Dalton’s atomic theory specifically of chemistry. would a little understanding of how stated that elements consisted of tiny chemical formulae and equations are particles called atoms. It further said that Periodic Properties of written. the reason an element is pure is because Elements all atoms of an element were identical Laws of Chemistry Before the Russian chemist Dmitri and that in particular they had the same Mendeleev came up with the periodic The real joy of learning chemistry comes mass. It also said that the reason elements table of elements in 1869, understanding from understanding its basic laws. If we look differed from one another was that atoms and remembering the properties of all the at the history of science we will come of each element were different from one 63 chemical elements known at that time across numerous instances where a another; in particular, they had different was a stupendous task. Mendeleev was sudden spark lit up a dark tunnel leading masses. Dalton’s theory also said that able to bring a system of classifying the to the solution of a long-sought problem. compounds consisted of atoms of elements which made the job easier. Chemistry also evolved in small steps, different elements combined together. He Although Mendeleev arranged the each marked by a unique discovery. used his own symbols to visually represent elements in order of increasing atomic One of the first big breakthroughs in the atomic structure of compounds. mass, which was incorrect, his periodic our understanding of chemistry came in There are millions of chemical table brought some order in an apparently 1803 when English physicist, meteorologist compounds formed by elements in random collection of elements. and chemist John Dalton proposed a different combinations; yet all of them are Mendeleev also did a few things that rational atomic theory to explain the facts guided by three simple laws of chemical made his table useful. He realised that the combination, which were propounded physical and chemical properties of Carrying between 1785 and 1806. elements were related to their atomic mass matters further, The law of conservation of mass was in a ‘periodic’ way, and arranged them so the French discovered by French chemist Antoine that the elements with similar properties chemist Pierre Laurent Lavoisier about 1785. It states that fell into vertical columns, or ‘groups’, in his Eugene during any physical or chemical change, table. Marcelin the total mass of the products remains Berthelot went equal to the total mass of the reactants. A major about John Dalton formulated the law of multiple synthesising proportions in 1803. According to this law, turning point organic if two elements form multiple compounds, in chemistry compounds the ratios of the masses of the second was the systematically, element combining with a fixed mass of refutation of turning them the first element will be in ratios of small the long held out in scores whole numbers. Three years later, the during the French chemist Joseph Proust stated the ‘vital force’ Robert Bunsen Gustav Kirchhoff 1850s. law of constant proportion, which states theory SCIENCE REPORTER, APRIL 2011 10 Cover Story The work of William Lawrence Bragg created a new science of X-ray crystallography.