Introduction to Chemical Sciences PDF

UNIT 1 INTRODUCTION TO CHEMICAL SCIENCES SESSION 1 SESSION 1: GENERAL INTRODUCTION You are warmly welcome to the first Session of this Unit. This session will look at general introduction to th...

UNIT 1 INTRODUCTION TO CHEMICAL SCIENCES SESSION 1 SESSION 1: GENERAL INTRODUCTION You are warmly welcome to the first Session of this Unit. This session will look at general introduction to the course man and his environment and brings out the relevance introduction of chemical science to our day-to-day activities. Objectives By the end of this session, you should be able to: (a) state the importance of chemistry; and (b) prepared for the reading ahead. Now read on… 1.1 General Introduction The course Man and His Environment seeks to provide some level of science to students with or without any science background. The focus even though is on science, emphasis would be put on the chemical science. The studying of chemistry has been declared as an essential part of most curriculums. This is because; so many subjects share an essential tie to chemistry. Subjects such as; Agriculture, Medicine, Engineering, Geology, Biology or one of the many other related areas of the study share the knowledge of chemistry. Chemistry by its varying nature is a central science. In any area of human activity that deals with some aspect of the material world, concern invariably arises about the fundamental nature of the materials involved: their composition and endurance, how they interact with other materials and with their environment, and how they undergo change. Chemicals have become part of the various activities of human kind today. Thousands of chemical products make up the food we eat, the cars we drive, and the medicine we use. We have become increasingly aware that the widespread use of some chemicals has had a profound effect on our environment. To be a responsible citizen you will need to be informed on many complex issues of chemistry and the use of chemicals. You can fully appreciate and analyze the complex issues put before you if you keep the relevant chemical principles in mind as you read and study current events. CoDEUCC/ Post-Diploma Programme 3  UNIT 1 GENERAL INTRODUCTION SESSION 1 Changes in materials occur all around us. For example, trees change colour in autumn, snow melts and iron rusts. Such changes have long fascinated people and have prompted them to look more closely at nature’s work in hopes of better understanding themselves and their environment. Chemistry is the science that is concerned primarily with matter and the changes it undergoes. The course will look at the basic chemistry and then how chemistry affects man and his environment. I hope this course would enable you understand some basic principles in chemistry. 1.2 To the Reader This book tries to answer some of these questions:  What is science and chemistry about?  Who are scientists or chemist?  How does science affect my life? In this book you will find some answers to these questions and enough to make you want to find out more about chemistry and science. Science has been carried out by all sorts of people all over the world for hundreds of years. Some scientists are interested in making new types of plants-they might be biologists, farmers or geneticists. Others may want to know how to make better parts (chip) for our computers – they might be physicists or chemists. Others are interested in the weather –meteorologists. Some scientists write and think and try out ideas about things using computers, such as theoretical physicists trying to explain how the solar system first came into existence. Other scientists can’t do experiments in the normal sense because their subject is a long way away, such as astronomers studying the stars. Many of us can behave like scientists when we try to solve a problem. We look for solutions and try out systematically those that seem reasonable – we test out our ideas; farmers, engineers and investors all use science in their work. Part of learning science is about knowing some of the scientific knowledge that has been discovered. This book can only tell you some of the enormous amount of information we have about the natural world. We hope it will make you want to know more. Science has something to say about how we ourselves work-our bodies. It can help us understand health and sickness, how new plants and animals are made. It can explain why a child has some features of its parents. Science has something to say about where human beings came form and tries to understand how the stars and planets came to be there. It has theories about these and other natural events in 4 CoDEUCC/Post-Diploma Programme  UNIT 1 INTRODUCTION TO CHEMICAL SCIENCES SESSION 1 the world which it has built up by measuring, collecting information and thinking about, what it all means. Science helps us understand how to use the resources of the world, to gain control over our environment and suggests ways to use knowledge sensibly. Science and technology have developed machines to make life easier, to use fuels to create a more comfortable life, make chemicals for medicines and control pests. Inventions such as the wheel, printing, telephones and computers have created new opportunities for us, but some have created problems too; plastic waste which will not rot, is an example. In many ways, science affects your life. You can choose to ignore it but you can’t avoid its effect. We hope this book will help you understand it better; and make you want to study science. Whatever you do with your life, you will wish to have an opinion about some current events which relate with science. Some knowledge of science will help you: but finding out about science will be even more helpful. This book contains some chemistry organized in a way that helps you link them to their life and the environment. Cross-referencing throughout the text will help you to see these links. It will give you a broad introduction to chemical science and enable you to study science at a higher level later, especially if you want to be a scientist. 1.3 Chemistry as an Experimental Science Chemistry is about everything in the human environment. This environment is made up of substances. Chemists study how the substances behave and try to understand why it is that the substances behave as they do. Chemists analyse substances in order to understand them. This means that the substances are taken apart in order to find out what they are made of and how they are put together. The substances are analysed through experiments. The experiments help to answer some questions about the substances. If a student decides to find out what a candle is made of, the student may carry out a number of experiments to obtain results that will help him or her to answer some questions about the candle. Questions that may be asked are: a) What would happen if a candle is allowed to burn in: (i) a plentiful supply of oxygen; (ii) an insufficient supply of oxygen? CoDEUCC/ Post-Diploma Programme 5  UNIT 1 GENERAL INTRODUCTION SESSION 1 b) What did happen when the candle burned? The products formed in a) (i) and a) (ii) can be analysed in order to answer this question. c) Why did it happen? Here the student tries to synthesize or combine the products of the experiment to produce the material of the candle. Other starting materials can also be used. Remaking the material of the candle will help the students to understand why the products were formed. The questions are the usual ones chemists ask when investigating the nature of a substance. Experiments are carried out to find answers to each question. Each question and its answer from experimental results lead to a better understanding of the nature of the substance. Self-Assessment Questions Exercise 1.1 1. Define chemistry. 2. Why is chemistry an essential part of most cubiculum? 3. Give three examples of changes that occur in materials in man’s environment. 4. There are many chemical products that support human life. List any three. 5. State five subjects that share the knowledge of chemistry. 6 CoDEUCC/Post-Diploma Programme  UNIT 1 INTRODUCTION TO CHEMICAL SCIENCES SESSION 2 SESSION 2: BACKGROUND OF CHEMICAL SCIENCE Welcome to Session 2 of Unit 1. In this session, we shall look at the history of chemical science. We shall also discuss the importance of chemical science. Objectives By the end of this session, you be able to: (a) state what chemistry has done to mankind; (b) explain how chemistry developed through the period; and; (c) be prepared for the readings ahead. Now read on … 2.1 Background of Chemical Science Background of chemical science would give the reader an insight into how the chemistry began to be known as the chemistry we have today. It gives the historical background of the chemical science. For centuries the work of chemists has been of interest to people all over the world. The study of chemistry has changed the whole way of human life and, in many ways made it more comfortable. Through chemical research many useful products have been produced and continue to be produced. These products include cloths, drugs, artificial goods, plastics, fuels, fertilizers, insecticides and weed killers. Some of this products are life saving and life supporting. Chemists like many other scientists use the scientific methods. Some of the steps involved in the scientific method are observation, investigation, prediction and conclusion. Chemistry, as a scientific discipline, can be defined as the study of the composition and structure of matter and the various changes that matter undergoes when alone or when combined with substances under different conditions of temperature and pressure. Chemistry serves to teach chemical principles within the framework of real-world application. The understanding of chemistry is fundamental to the understanding of almost everything in nature. And as a matter of course, chemists are able to modify matter and apply the knowledge of natural matter to the synthesis of many new kinds of products from matter. CoDEUCC/ Post-Diploma Programme 7  UNIT 1 BACKGROUND OF CHEMICAL SCIENCE SESSION 2 Historically, the natural sciences have been associated with observations of nature particularly our physical and biological environment. With the gradual advancement of scientific disciplines, the relationship of chemistry to other sciences has become very close, and the boundaries of individual disciplines have become more blurred than ever. From a global outlook, some understanding of chemistry might be beneficial to the average person in his dealings with major social issues such as pollution, population explosion and provision of adequate energy and food, for the millions who will live in the 21st century. The world population is expanding at an ever-increasing rate, as the present total of 5.7 billion is expected to double in the next 40 to 50 years. The million-dollar question hinges significantly on how everyone will be housed, clothed and fed. How the present and future generations can prevent the contamination of planet earth. How can generations yet to be born reverse the damage being inflicted on planet earth, when the present generation seems to know nothing about consequences of their activities? How can the present generation prevent causing more harm and damage to our environment? None of the above questions can be fully addressed without the application of chemistry. Hence, chemistry plays a very significant role in the maintenance of clean and life- sustaining environment. Indeed, most pollution problems are blamed on industrial and synthetic chemicals. But ironically, most of the environmental problems of present and past generations, for example, the contamination of drinking water – were solved principally through the application of chemistry and related disciplines. The phenomenal rise in human life expectancy as well as the material quality of life in recent years is due in no small measure to the applications of chemistry and chemical technology. 2.2 The Importance of Chemistry to Man Indeed, human life is maintained as a result of biochemical processes that are continuously taking place within the human body. For example, the air we breathe into our lungs is a mixture of chemical compounds and elements in their gaseous forms; oxygen, nitrogen, carbon dioxide and water vapour. The oxygen is transported into the lungs across certain membranes before its reacts with the haemoglobin in the blood to form oxyhaemoglobin, without which vital processes in the cells and tissues would not take place. 8 CoDEUCC/ Post-Diploma Programme  UNIT 1 INTRODUCTION TO CHEMICAL SCIENCES SESSION 2 In the agricultural sector chemistry is applied in the growth of plants and the preservation of crops and grains in the form of herbicides and pesticides. The perfume and cosmetics industry thrives and makes life smell real good-thanks to the application of chemistry. The promotion of personal health and hygiene by the use of drugs, soaps and disinfectants, could not have been possible without the enormous input of chemical knowledge. The natural and synthetic fibers that are used to make clothes and other materials have all been processed or developed from chemicals and through the application of chemistry. The house we live in as well as the furniture and comfortable mattresses in our homes and bedrooms have been made available through the ingenious application of chemistry. Building materials like cement, iron rods and other chemicals such as paints, lacquers, varnishes, plastics, ceramic tiles etc are made by the application of chemical technology. Almost all items of entertainment and household equipment (radios, television sets, videos deck, microwaves, cooking utensils) are all developed or fabricated from specialized chemical products. Indispensable items like plastic bags, papers, dyes, solvents and writing liquids, petrol, lubricant and bitumen, are all made available to us through the magic of chemical process, development and synthetic ingenuity. The magic of chemistry is still alive and will keep providing us with the requisite tools to live meaningful lives with the advent of the 21st century and beyond. This book will look into the chemical view of the world, which is based on observations and facts. Chemistry is a physical science that is also based on facts and observations. A scientific fact results from repeated observations of events that produce the same result each time the event is carried out. (For example water boils at 100oC at sea level anytime – anywhere – that’s a scientific fact, obtain by observation). The knowledge of chemistry adds a new dimension to everyday life, which is based mainly on observations and facts, and this booklet delves into the chemical view of life in this world. Have you ever walked down a path through the forest in autumn and wondered why leaves change their colour? Perhaps you have marveled at the vivid colours? Of a fireworks display or sat around a campfire at night, captivated by the bright flames? These colourful phenomena are the results CoDEUCC/ Post-Diploma Programme 9  UNIT 1 BACKGROUND OF CHEMICAL SCIENCE SESSION 2 of chemical changes. Chemistry does not happen only in laboratories. It occurs all around us right before our eyes. Chemistry deals with all the multitude of materials and changes we see around us that make our world so diverse, beautiful and at times mysterious. It explains the rusting of iron nails, the melting of ice, the digestion of a candy bar, the colours of your vacation slides, the baking of bread and the aging of a person. People have used chemical reactions to make their lives easier for hundreds of thousand of years. Fire was almost certainly the first reaction to be used this way. The people who discovered fire were seeking light and warmth, of course, not knowledge of other reactions that have been known for thousands of years include copper smelting (heating copper compounds to make the metal), fermentation (combining fruits or grains with yeast to produce alcoholic beverages), saponification (heating fats and oils with a base, obtained from wood ashes, to make soap), and papermaking (converting plant fibers to paper). All of these processes are still in use today. Think about paper. The first paper making process was developed by the Chinese court official Ts’ai Lun in about 50 AD. Since then paper has been the primary medium for sharing, distributing and storing information; this book is an example. Communication became easier – the world shrank – as paper became more available. One goal of early scientists was to figure out what matter is. Such questions as “what is a rock?” and “How can I convert lead into gold?” were taken seriously. The essential tools of science, the methods of asking and answering questions took more than 2500 years to develop. Early attempts were deeply rooted in philosophy. In fact, natural philosopher was the term used for those interested in science right up to a century ago. Even today the highest degree you can earn in science is the Ph.D – Doctor of philosophy. 2.3 History of the Chemical Science What follows is a necessarily brief and oversimplified summary of the earliest chemical theory and practice. As you read through the rest of this section, note the shift in emphasis from the abstract to the concrete as people learned more and more about the world around them. The Babylonians carefully observed the sky and developed a complex mythology loosely based on what they saw. Some of those myths came down to us through the 10 CoDEUCC/ Post-Diploma Programme  UNIT 1 INTRODUCTION TO CHEMICAL SCIENCES SESSION 2 Greeks in the form we call astrology. Those myths had a greater scope in ancient times than they do now. The Greeks thought that the stars and planets controlled not only human lives but also substances. The sun controlled gold, and the moon, silver. Mars was associated with iron and Venus with copper. The Greek philosopher Thales (640-546 BC) traveled to Egypt. There he learned from both the intensely mystical Babylonian culture and the more practical culture of his North African hosts. Later he proposed that water was the basis of the universe. This seemed to be a perfectly reasonable conclusion, because water is found everywhere – in plants, in animals, and in the ground. Furthermore, water can be converted from its liquid form into either a solid or a gas. Since all matter on earth is in one of these three states, water makes a very sensible choice as the basic element. According to Babylonian myth, the universe was created from water. Other philosophers followed with competing ideas. Empedocles (about 492 – 432 BC) combined several of these proposals into one. He theorized that there were four basic elements: earth, air, water and fire. He viewed transformations of matter as being governed by such things as love and strife. Aristotle (384 – 322BC) adopted much of this system. He thought that the four elements postulated by Empedocles were not truly fundamental but arose from the combination of characteristics that were even more basic. Fire was hot and dry, air was hot and moist, water was cold and moist, and earth was cold and dry. Aristotle also maintained that gold was the most perfect metal. Alchemists used this kind of thinking for 2000 years after Aristotle. While trying to remove the imperfections from baser substances to make gold, they developed some useful recipes for making other things. As European civilization collapsed into the Dark Ages, the young and vigorous Arabic civilization took up alchemy. The Arabs borrowed ideas and methods from the Chinese (including papermaking) and made substantial contributions of their own. Europeans were recovering their own cast-aside heritage from the Arabs (with Arabic modifications and improvements) by about the thirteenth century. 2.4 Important Philosophical Trends in Chemistry In later ages in Europe natural philosophers and mathematicians modified, extended, and in many cases replaced the ideas of the earlier philosophers and alchemists to produce modern science. The details of this fascinating CoDEUCC/ Post-Diploma Programme 11  UNIT 1 BACKGROUND OF CHEMICAL SCIENCE SESSION 2 transformation are beyond the scope of this book, but one historian of chemistry, Edward Farber, has identified three important philosophical trends. First, substances had to be viewed as independent of the gods and planetary influences before modern chemistry could arise. This was difficult, because the same alchemical symbols were used for some of the planets and elements. Alchemy finally withered away not long before 1800. Second, words like love and strife had to be limited to human affairs and not applied to substances and their actions. Modern chemists view reactions as arising from impersonal forces. Physicists, in particular Sir Isaac Newton, established this viewpoint during the 1600’s by using such emotionless terms as gravity to describe natural forces. Finally, the chemical elements had to be viewed as specific, distinct substances in their own right, rather than as manifestations of universal principles. Natural philosophers had fully accepted this by the end of the 1600’s and dozens of elements were quickly discovered after that. Another essential change involved the distribution of knowledge. The early scientists, Al-chemists, often kept their methods and discoveries secret. They usually passed on their methods only within their families, and if they wrote them down, they deliberately made their texts hard to understand. Leonardo da Vinci did his work in a scientific spirit, but wrote his notes backwards – an effective code in an era when few people could read well. Furthermore, most of da Vinci’s work was not published until long after his death. Most modern chemists and other scientists see their obligations very differently. They see themselves as having a duty to publish their results, to make them as widely known as possible. This does not mean that chemists are taught this vocabulary, and though it may be difficult to master, it isn’t secret. As time went on, chemists refined their methods and made them more precise. Often this meant making more numerical measurements and making them more carefully. One of the earliest practitioners of careful measurement was the French chemist Antoine Lavoisier (1743 – 1794). Lavoisier was affiliated with the tax collection department and had access to the best available balances. More importantly, he understood the need for accurate weighing. 12 CoDEUCC/ Post-Diploma Programme  UNIT 1 INTRODUCTION TO CHEMICAL SCIENCES SESSION 2 He performed experiments and measurements to test the theory that when a substance, a fluid called phlogiston, is transferred from one place to another the mass does not change. Although the phlogiston theory was widely accepted in the eighteenth century and had much to recommend it, Lavoisier was disturbed about some of the properties of this proposed fluid. It apparently had a positive mass some of the time and a negative mass at other times. His experiments demonstrated either that phlogiston did not exist or that, if it did, it had no mass at all. Self-Assessment Questions Exercise 1.2 1. State two reasons why it is important to study chemical science 2. The Greek philosopher who traveled to Egypt is called? 3. List some of the steps involved in scientific methods. 4. People have used chemical reactions to make their lives easier. What was the first reaction to be used this way? 5. In the agricultural sector chemistry is applied in the growth of plants and preservation of crops and grains in the form of ………… and ……………. CoDEUCC/ Post-Diploma Programme 13  UNIT 1 BACKGROUND OF CHEMICAL SCIENCE SESSION 2 This is a blank sheet for your short notes on:  issues that are not clear  difficult topics if any. 14 CoDEUCC/ Post-Diploma Programme  UNIT 1 INTRODUCTION TO CHEMICAL SCIENCES SESSION 3 SESSION 3: INDIGENOUS SCIENTIFIC PRACTICES In the previous session, we discussed the history of chemical science and its importance. In this session we shall consider some indigenous application of chemical science. Objectives By the end of this session, you should be able to: (a) state five indigenous chemical practices of our people; (b) describe how chemistry developed through the period; and (c) be prepare for the readings ahead. Now read on… 3.1 Indigenous Scientific Practices Indigenous scientific practices would give the reader an insight into how chemistry can be used to explain traditional activities of the indigenes. This also explains that science has been practiced long before the white man came to Ghana. Science has been practiced over the years long before the advent of the white man to Ghana. However the name science was alien at the time until it finally explained the principles they were using at the time as scientific concept. We shall look at the production of soap and alcohol. Also we would consider the use of charcoal and wood ashes. Then also, we will consider simple indigenous acid-base reactions. 3.2 The Use of Charcoal Charcoal has been used over the years even long before gas; electricity and kerosene became sources of fuel for domestic and commercial purposes. Charcoal has ever since, till today, been on an enormous scale of consumption as fuel for cooking and boiling herbs as far as medicinal purposes are concerned. As a source of fuel, charcoal has been used for heating ‘box’ pressing irons, heating the home in cold weather as well as in cooking foods, in most homes and places where charcoal is known, it is preferred for use as fuel for cooking foods. That is boiling, frying, grilling, roasting as well as baking. According to our old folks, dropping a piece of charcoal into a pot of soup or stew that seems to have slightly gone bad will bring it back to normalcy and restore it CoDEUCC/ Post-Diploma Programme 15  UNIT 1 SESSION 3 INDIGENOUS SCIENTIFIC PRACTICES taste. Well, scientists have not proven this but it works like magic. For cleaning of kitchen utensils, charcoal is ground and mixed with ground eggshell and white clay, which gives a very good abrasive and cleans effectively. It can also be used with the tip edge of unriped plantain to clean the teeth. Charcoal is also used as the base for most traditional medicines whose curing power is unbeatable. Most concoctions in traditional homes are charcoal base. For instance ground charcoal can cure stomachache almost instantly. 3.3 Local Preparation of Soap Locally, peels of food stuff, the waste cocoa pods and edible oil are the main starting materials for the production of soap. This soap has been in use for over hundreds of years. Presently it has undergone some kind of phase lift; however, the method of preparation is the same as it used to be. The difference now is just the method of packaging the product, the content remain the same. 3.3.1 Procedure for the Production Materials collection; waste cocoa pods, or peels of some food stuff (plantain, cassava etc.) are collected and dried for sometime. The dried material is burnt in excess oxygen into ashes. The ashes are put into water for some time and then the suspension filtered. The filtrate is what is used in the soap making. The next thing is the extraction of palm oil from the palm fruits. The palm fruits are boiled for sometime and the juice squeezed out. It is then mixed with water and then boiled; because water and oil are unmixable, the oil settles on the surface of the water and is easily scooped off. The oil is then heated to further remove any impurities present in the course of its preparation. The refined oil is then mixed with the filtrate from the ashes and heated for sometime until the soap is formed. The heating continues until all the excess water is boiled off. The soap then remains as slurry, soft and black substance. The method of soap production as we know today follows the same principle. Except that the materials keeps changing. The filtrate is known today as potassium hydroxide which is similar to the caustic soda used in large scale soap productions today. The process is science known today as soponification. 3.4 Local Distillation of Alcohol From the palm wine it is stored for about three days to allow fermentation to take place. After three days, the fermented palm wine is heated in a large barrel which has been completely closed with only a tube connected from the upper end, where the steam vapour is passed through a pool of cold water. The pool of water serves 16 CoDEUCC/Post-Diploma Programme  UNIT 1 INTRODUCTION TO CHEMICAL SCIENCES SESSION 3 as the cooling agent to cool the tube. And the alcohol in the vapour state is converted to liquid state when the hot vapour comes into contact with the cooled tube. This tube leads to another container at another end into which the alcohol in the tube is discharged. However, as the content is heated and boiling takes place, the vapour generated comes out from the tube and converted back to the liquid form. The first distillate is about 80% alcohol. The percentages of alcohols are tested normally with flame. The colour of the flame determines the strength of alcohol. Blue flame depict strong alcohol whiles yellow a very weak alcohol. This process is highly scientific because, the process is what is now known as distillation. This means that, some of our indigenous activities were scientific except that we did not develop them. 3.5 Indigenous Acid-base Reaction (a) The reaction of “Kanwu” In the local scene, whenever one prepares tomato stew and the acidity of the sauce is too much, “kanwu” is added to neutralize that acid content. The phenomenon is in practice even today but it is only that the concept was not known as a scientific process. It is entirely an acid base reaction which result in the production of salt and water. This is referred to as neutralization reaction. The “Kanwu” has been determined to contain sodium carbonate and sodium hydrogen carbonate. (b) The Reaction of “hyire” (Kaolin Clay) Heart burns and stomach upset over the years have been treated with a substance know as “hyire” in most local communities in Ghana. Heart burns or indigestion is as a result of outpouring of acid which lowers the pH to a point at which one becomes uncomfortable in the stomach. This means that any remedy to that discomfort should contain a base to neutralize the acidic effect in the stomach. Once “hyire” is consumed the acidic effect in the stomach is neutralized. The hyire is basic and it is able to neutralize the acid. The “hyire” is known today as kaolin. CoDEUCC/ Post-Diploma Programme 17  UNIT 1 SESSION 3 INDIGENOUS SCIENTIFIC PRACTICES Self-Assessment Questions Exercise 1.3 1. List the main starting materials for the local preparation of soap. 2. The filtrate from the ashes is also known as………….. 3. Why is palm wine stored for about three days? 4. State one important use of Kaolin? 5. The colour of flame determine the strength of alcohol. What colour depicts strong alcohol and which depicts weak alcohol? 18 CoDEUCC/Post-Diploma Programme INTRODUCTION TO CHEMICAL SCIENCES UNIT 1 SESSION 4 SESSION 4: DISCOVERIES IN SCIENCE In this session we shall discuss the discoveries of some scientific principles and their importance. Objectives By the end of this session, you should be able to: (a) explain what science is; (b) state at least three importance of studying science; and (c) list at least three important scientific discoveries. Now read on… 4.1 Discoveries in Science Many great scientists made their discoveries using the scientific method. In 1926, the British bacteriologist, Alexander Fleming, worked in a London hospital looking at the bacteria, staphylococcus. He was examining plate cultures of staphylococcus when one day he noticed an unexpected mass of fluffy mould growing in the cultures. After some time these masses became dark green in colour and were later identified as Penicillium notatum, similar to the mould that grows on orange peels. Five days after he noticed this unexpected growth of mould, Fleming discovered that it secreted (produced) a substance, which was able to permeate (travel through) the culture medium. Around the regions where the mould grew, a clear zone was observed. As the mould grew, so did the clear zone where no Staphylococci could exist also grew. At the time Fleming concluded that the mould, which he named Penicillium, could have produced a substance, which could fight bacterial growth. This theory was not accepted; even through he conducted many more experiments with careful controls in an attempt to prove this scientifically. At the beginning of the Second World War, Howard Florey was trying to find substances that might be capable of fighting the infections that developed in wounds. He read Fleming’s report on his discovery and conducted further experiments. His research later led to the acceptance and development of penicillin as an antibiotic. CoDEUCC/ Post-Diploma Programme 19  UNIT 1 DISCOVERIES IN SCIENCE SESSION 4 In 1996, Becquerel was investigating the action of bright sunlight on uranium salts on a photographic plate. These plates were securely wrapped, but when placed near the uranium compounds the plates became fogged, despite the fact that they were covered. Something must have gotten through the covering, and it was suggested that the uranium spontaneously omitted some rays, then known as Becquerel rays. The theory was modified, through further experiments of Rontgen and the Curies to explain the cause of the forging. It was found that uranium gives off particles quiet naturally (spontaneously) – a process known as radioactivity. It was these radioactive particles (rays) that penetrated the covers of the plates. One experiment may lead to a very unexpected conclusion, as you have seen above. The importance of research and repeated testing in science is clear. These are not typical of scientific method but more of an accident, which can be interpreted by the scientifically trained mind. In order to test and verify their observations, both Fleming and Becquerel needed to use the scientific method. They tested their hypotheses by further experiment, checking and rechecking their results, until finally they could say that their original observations were correct. 4.2 The Discovery of Vaccination Edward Jenner, an English physician, was the originator of vaccination. He suffered from smallpox as a child and from the time he became a pupil of the great John Hunter he was interested in the disease. There was a popular belief in the countryside that persons who contracted cowpox were then immune from smallpox. This popular belief became a conviction in his mind and he set out to prove it. He tried to show that inoculation of the cowpox virus by the arm-to-arm method from person to person would eventually provide an available source of cowpox lymph. Secondly, he predicated that after transmission through many individuals, the virus might lose its immunizing power. In 1798, he set out to investigate the above two hypotheses. After numerous experiments, he published his results. He took the view that vaccination carried out with lymph taken from the right stage of the pock would give complete and permanent protection throughout life against smallpox. Unfortunately, he was not correct although his patients that did contract smallpox only suffered a minor attack. Thus his many experiments were not complete and he needed to go on further.. 20 CoDEUCC/ Post-Diploma Programme INTRODUCTION TO CHEMICAL SCIENCES UNIT 1 SESSION 4 Nevertheless, although no one else attempted to extend work on this problem, vaccination spread throughout England. In 1880, Pasteur continued the experimental work of Jenner with his inoculation of fowls against fowl cholera. 4.3 The Discovery of Oxygen The history of the discovery of oxygen shows a dogged pursuit of experimentation and the scientific method. In the first part of the eighteenth century, a number of men were studying gases. Stephen Hales, Joseph Black and Joseph Priestley had all experimented to isolate and examine the gases we now call carbon dioxide and oxygen. By 1775, the position was becoming complicated and chaotic. So much confusion existed, that chemistry was building up strange myths about various substances. At that time, there emerged a man who was able to look at the whole scene and its confused pieces and see a way of turning them into a pattern. His name was Lavoisier; he was twenty-eight years of age when he embarked on a monumental body of directed experiments to bring the confusion into unity. Two years later he made a more detailed historical survey of what had been done and added experiments and arguments of his own. He came to feel that it was not the whole air but a particular gas in the air, which entered into the process of combustion. Finally, he decided that all acids are formed by the combination of non-metallic substances with eminently respireable air, so he described this as the acidifying principle, or the Principe oxygine – hence oxygen acquired the name that it now possesses. Lavoisier was extremely ingenious in experimentation, but at the same time he took the work of his contemporaries and used it to some purpose. 4.4 The Scientific Discovery of Teflon and Serendipity Louis Pasteur once remarked that: “In the science of observation and scientific research, success favours the prepared mind”. Yes, sometimes-useful discoveries are the result of what might be called “accidents” or “serendipity” (unexpected discovery by change). Of course, these “accidents” had to have happened to the right kind of individuals with prepared and receptive minds. The real secret is that when and unexpected experimental result turns up, those with prepared minds look up on it as an opportunity. They become curious and look out for all minute details. CoDEUCC/ Post-Diploma Programme 21  UNIT 1 DISCOVERIES IN SCIENCE SESSION 4 They want to know more about what has happened and why it happened. The discovery of Teflon is one such tale of serendipity. Teflon is a material famous for its use in nonstick cooking utensils. In 1938, Roy J. Plunkett discovered Teflon accidentally. At the time, Plunkett was making new kinds of chloro-fluorocarbons for possible use as refrigerants. To do this required the use of a starting material, terafluoroethylene, a gaseous chemical that was stored in tanks and withdrawn as and when it was needed. In Plunkett’s own words, one day the following incident happened: “Soon after the experiment started, my assistant called to my attention that the flow of tetrafluoroethylene had stopped. I checked the weight of the cylinder and found that it still contained a sizable quantity of the material, which I thought to be tetrafluoroethylene. I then removed the table to pour a white powder from the cylinder. It was obvious immediately to me that the tertrafluoroethylene had polymerized and the white powder was a polymer of terafluoroethylene”. Instead of putting aside the material as useless, Plunkett immediately set about to investigate its properties. The white powder turned out to be resistant to heat and to have such a low surface friction that nothing sticks to it. It was a great discovery by chance. Self-Assessment Questions Exercise 1.4 1. What is science? 2. What was Lavoisiers opinion about Oxygen. 3. Match the following discoveries to the scientist responsible. Scientist Discovery A. Roy J. Plunket A. Penicillin B. Edward Jenner B. Radioactivity C. Henry Becquerel C. Teflon D. Alexander Fleming D. Pasteurization E. Louis Pasteur E. Vaccination. 22 CoDEUCC/ Post-Diploma Programme  UNIT 1 INTRODUCTION TO CHEMICAL SCIENCES SESSION 5 SESSION 5: TIME NEEDED FOR TECHNOLOGY DEVELOPMENT In Session four we discussed the history of some scientific discoveries. In this session we shall discuss the applications of some scientific principles. Objectives By the end of this session, you should be able to: (a) list at least three important chemical technologies; and (b) state at least three innovation periods for some technologies. Now read on… 5.1 Time Needed For Technology Development Scientific knowledge/technology and understanding often take many years and many people to reach acceptable conclusions. Rarely is it achieved quickly, as the method itself demands repeated testing and experiments to ensure that the discovery was not an unusual happening, or a chance event. Fact has to be proven, and this may take many generations, with disappointment for scientists whose original idea was unused or rejected, only to be proved many years later through extended research. 5.1.1 Fridge Technology Most of us use refrigerators and air-condition in our homes and offices, and in cars, but we are not aware how and on what they operate, and the effect of refrigerants on our lives. The background of refrigeration and air-conditioning technology is rooted in some interesting history of chemistry. Refrigeration, as we know it today, has been in use since the late 19th century. The process of cooling requires a liquid that absorbs heat as it evaporates, or releases heat when it condenses (i.e. a volatile liquid). This liquid should be such that it can be continuously cycled through evaporation and condensation without breaking down. At the turn of the 20th century, the liquids used as refrigerants were mostly flammable or toxic. The story goes that one day, the director of research at General Motors, Charles Kettering, passed along a challenge to Thomas Midgley, a young, engineer: He wrote: “The refrigeration industry needs a new refrigerant if we ever expect to get CoDEUCC/ Post-Diploma Programme 23  UNIT 1 SESSION 5 TIME NEEDED FOR TECHNOLOGY DEVELOPMENT anywhere”. Midgley and a colleague did some thorough research in various chemistry laboratories. Midgley’s research report to the director contained one interesting and innovative paragraph. It read like this: Seemingly, no one previously had considered it possible that fluorine might be non- toxic in some of its compounds. The refrigeration engineers had certainly disregarded this possibility. If the problem were to be solved by the use of a single compound rather than a mixture, then that compound would certainly contain fluorine. The young engineer and his colleagues settled on an experiment with a new chemical, which they could make in the laboratory. One of the necessary ingredients was a fluorine chemical that was scarce, so they purchased the available supply in five small bottles at a go. One of the bottles was used to make the first sample of the new refrigerant, and a guinea pig did not die. In fact, it wasn’t even irritated. The experiment was a good one. A second sample made from the same chemical in a different bottle did, however, kill the guinea pig. A careful investigation revealed that only the first bottle contained pure material. It was therefore a contaminant that killed the guinea pig, not Midgley’s newly prepared chemical. Midgley wrote in his notebook: of the five bottles, one had really contained good material, and we choose that one by accident for our first trial. Had we chosen any one of the other four, the animal would have died in the first instance as was expected by everyone except ourselves. I believe we would have given up on the experiment”. And the moral of his last little story is simply this: You must be lucky as well as have good associates and assistants to succeed in the world of applied chemistry. The outcome of this experiment was the widespread presence of refrigerators in every home. With the advent of reliable refrigerators, food spoilage diminished, and the food processing industry expanded to the production of frozen food after the Second World War. This story is the beginning of the development of chlorofluorocarbons, often referred to as CFCs, which were then thought to be much less hazardous refrigerants. The use of CFCs rapidly expanded throughout the 1950s and 1960s as 24 CoDEUCC/Post-Diploma Programme  UNIT 1 INTRODUCTION TO CHEMICAL SCIENCES SESSION 5 all kinds of new consumer products were brought to the market. The properties of CFCs also made them ideal for propellants in aerosol cans and for blowing tiny holes into materials such as the polyurethane foam used in pillows and furniture cushions. No apparent demerits of CFCs were noted in the 1950s and 1960s. 5.1.2 The Problems with Fridges The problem being created by CFCs did not surface until the 1970s apparently because scientists were not aware of the fate of these very stable compounds when they were released into the environment. By the 1980s it had become quite clear that CFCs are carried unchanged into the stratosphere, where they interact with ozone and destroy it systematically. The result is the “ozone holes” which allows ultraviolet solar radiation to reach the Earth’s surface and this causes much damage to our skins. In 1987 industrialized nations that produce CFCs came together to draft a plan of action to reduce the industrial production of CFCs and set a target date of 1995, by which time all production of CFCs must cease. A new refrigerant R-134s, was proposed to replaced the old CFC based R-12. What this means in simple terms is that, a car that was designed to use R-12 for its, air-conditioning system (which includes almost all those made before 1992) cannot use the new R-134a unless the system is modified – which can be a costly venture to undertake. 5.1.3 Distinctions among Basic Science, Applied Sciences and Technology It might be useful to recognize the distinctions among basic science, applied science, and technology when reading about refrigerants, plastics, DNA fingerprinting etc. Basic science is the pursuit of knowledge about the universe with no short-term practical objectives for application of significant findings; for example, the biochemists who struggled for years to understand exactly how DNA functions within cells were engaged in basic science research. Applied Science, on the other hand, had well-defined, short-term goals for solving a specific problem. The search for a better refrigerant by Midgley and his colleagues is an excellent example of applied science: they had a clear cut, practical goal, and to reach that goal, they utilized recorded observations of earlier studies and analyzed them in order to make a predication. They then performed experiments to test their prediction. CoDEUCC/ Post-Diploma Programme 25  UNIT 1 SESSION 5 TIME NEEDED FOR TECHNOLOGY DEVELOPMENT Technology, which is also an application of scientific knowledge, is a bit more difficult to define. In a sense, it is the sum of the way we apply science to improve the context of our society, out economic system and the mode of industrial production. The first refrigerators and air-conditions designed to use CFCs were the products of a new technology. The rapidly expanding number of ways that DNA is manipulated to make new medicines or other marketable products is referred to as biotechnology. Table 1. Time Needed to Develop Technology for some Ingenious Ideas Number Innovation Time of Time of Innovation Conception Realization Period (Years) 1 Antibiotics 1910 1940 32 2 Cellophane 1900 1912 12 3 Hearth Pacemaker 1928 1960 32 4 Instant Camera 1945 1947 2 5 Instant Coffee 1954 1956 2 6 Nuclear Bomb 1919 1945 26 7 Nylon 1927 1939 12 8 Photocopying 1935 1950 15 9 Radar 1907 1939 32 10 Roll-on 1948 1955 7 11 Deodorant 1923 1939 16 12 Automatic Watch 1950 1956 6 13 Videotape Dec. 1895 Jan. 1996 0.08 Recorder X-rays in Medicine Regardless of the type of scientific discovery, there is a delay between the discovery and its technological application. The incubation intervals for number of practical applications of various types are given in Table1. The important point is that technology like science is essentially a human activity. Men and women make decisions about the uses of technology and priorities for technological developments. It is therefore essential that those who make technological decisions are well informed enough to critically evaluate the societal issues related to the technology. 26 CoDEUCC/Post-Diploma Programme  UNIT 1 INTRODUCTION TO CHEMICAL SCIENCES SESSION 5 As the story of CFCs illustrates, science and technology are constantly evolving, just like social conditions. When CFCs were introduced as refrigerants in the 1930s, hey were great advances, from the socio-economic point of view, since they replaced hazardous materials. In those early days, people were in the habit and assuming that natural processes would keep the environment clean and friendly. Today, we have seen that only controlled human activity would keep our environment clean and less hazardous. It is only by staying informed and sensitive to environmental pollution that we of this generation can adjust to changing times, and safeguard our environment for succeeding generations. Self-Assessment Questions Exercise 1.5 1. Why do technological developments often take much time? 2. What are CFC’s. 3. Why didn’t scientists realize the fate of CFC’s in the atmosphere that early? 4. What is technology? CoDEUCC/ Post-Diploma Programme 27  UNIT 1 SESSION 5 TIME NEEDED FOR TECHNOLOGY DEVELOPMENT This is a blank sheet for your short notes on:  issues that are not clear; and  difficult topics, if any. 28 CoDEUCC/Post-Diploma Programme  UNIT 1 INTRODUCTION TO CHEMICAL SCIENCES SESSION 6 SESSION 6: UNDERSTANDING OUR ENVIRONMENT This session will look at how our environment has change with time. It will discuss the use of environmental science in solving environmental problems. Objectives By the end of this session, you should be able to: (a) define the term environment and identify at least three important environmental concerns that we face today; (b) explain the scientific method and why it refutes or supports theories but never proves them beyond any doubt; and (c) apply the scientific method to problem solving. Now read on.... 6.1 What’s happening to the Frogs? In 1995, school children on a summer field trip to a Minnesota marsh discovered dozens of frogs with malformed, missing, or extra legs. The students’ questions about these deformities attracted public attention to frogs and what they might be telling us about our own environment. As the news spread, people became aware that, around the world, from Australia to Zimbabwe, scientists were finding amphibians in trouble. In some places, up to 60 percent of the frogs or salamanders had aberrant limbs, digits, eyes, or internal organs. Other species, like Costa Rica’s golden toads, that once were locally abundant, had apparently vanished in just a few years. What might be causing these problems? Many hypotheses have been advanced for the deformities and disappearances. Pesticides and herbicides that accumulate in marshes and ponds might be part of the causes of the problem. Since amphibians spend most of their lives in water, they easily absorb toxins through their thin skin. A number of synthetic chemicals are known to mimic hormones that regulate growth and development in animals. Toxic metals such as arsenic, mercury, selenium, and cadmium from industrial pollution or agricultural runoff also might play a role. Ultraviolet (UV) radiation from the sun is increasing in many areas because of damage to the stratospheric ozone shield, and frog eggs and young are known to be sensitive to UV radiation. In addition, parasites such as trematodes (flukes) are known to infect tadpoles and interfere with normal limb growth and development. Suggestion about sudden die-offs range from global climate change to acid rain, viruses, toxins, and habitat loss. CoDEUCC/ Post-Diploma Programme 29  UNIT 1 TIME NEEDED FOR TECHNOLOGY SESSION 6 DEVELOPMENT How can we choose among these opposing ideas? There are two main approaches to studying environmental problems such as these. One approach is observational: Look for associations between presence of a suspected agent and high percentages of deformed or dying animals. Are there more abnormal frogs in ponds near agricultural areas, for instance, compared to relatively “pesticide-free” areas? Of course, a simple correlation doesn’t establish causality, but it can suggest direction for further research. The other approach is experimental: Test various factors under carefully controlled conditions. Animals grown in laboratory conditions have been exposed to parasites, toxic chemicals, or UV light at precisely measured doses. Do more deaths and deformities occur in these experimental populations than in controls grown under exactly the same conditions except for the factor being tested? While this approach gives us much more precise information about the effects of the agent being studied, it can’t reproduce the complex interactions that occur in nature. So, what do we know about what’s happening to the frogs? Unfortunately, we are still not sure. After millions of dollars spent on years of research, the results are confusing and contradictory. Although some scientists claim to have definitive answers, no single agent or factor produces all the different kinds of deformities and mortality patterns observed in the field. The truth is, there may be no simple cause for all the diverse problems observed at different places and times. Varying combinations of some or all of these factors may be at work. What should we make of these problems besetting amphibians? Some people see this situation as an ominous warning that human activities are disrupting nature in ways that threaten not only other species but us as well. They see frogs as early- warming indicator species, much like canaries in a coal mine. Others warn that just because the deformed frogs look pathetic, we shouldn’t assume they are evidence of environmental disaster. Don’t rust to judgment, they caution, without more facts. This case study introduces several important themes in environmental science. What we are doing to other species and to our environment? How can science help us to understand these complex problems? When will we know enough to make a reasoned judgment? How can we know what to do or whom to believe when experts give contradictory testimony? We hope you’ll find information and inspiration in this book to help you understand the science involve in these questions and to become an informed environmental citizen. Welcome to a fascinating, and we hope, enjoyable voyage of discovery. 30 CoDEUCC/ Post-Diploma Programme  UNIT 1 INTRODUCTION TO CHEMICAL SCIENCES SESSION 6 6.2 Understanding our Environment The problems besetting frogs illustrate some of the complexity and importance of contemporary environmental issues. Humans actions are having widespread impacts on our world and the other organisms with which we share it. Science and technology have become pervasive forces, both to explain how things work and to reveal how we can make our environment safer, more comfortable, and more enduring. The knowledge being gained by scientists is fundamental to our ability to manage the earth’s resources in a sustainable manner and to improve the quality of our lives and those of our children. Environmental scientists work on many problems that critically affect our well-being in many ways. Because of the significance of its findings, an understating of environmental science is becoming increasingly necessary for any educated person. As you study environmental science you will learn about many serious problems. But environmental science can also be exciting, and highly gratifying. Environmental scientists explore coral reefs, live with great apes, collect ice samples from deep in glaciers, study exotic plant species and listen to whales as they study the world around us. They also examine the social institutions and built environment that we create for ourselves using science, technology, and political organization. There is room for many different kinds of interests and abilities within this broad discipline. Whether you are a professional scientist or a concerned citizen you can apply your knowledge of environmental science in enjoying the useful ways. 6.3 A Marvelous Planet Before proceeding in our discussion of current dilemmas and how scientists are trying to understand them, we should pause for a moment to consider the extraordinary natural world that we inherited and what we hope to pass on to future generations in as good – or perhaps even better – conditions than we found it. Imagine that you are an astronaut returning to the earth after a long trip to the moon or Mars. What a relief it would be, after experiencing the hostile environment of outer space, to come back to this beautiful, bountiful planet. Although there are dangers and difficulties here, we live in a remarkably prolific and hospitable world that is, as far as we know, unique in the universe. Compared to the conditions on other planets in our solar system, temperatures on the earth are mild and relatively constant. Plentiful supplies of clean air, fresh water, and fertile soil are regenerated endlessly and spontaneously by biogeochemical cycle. CoDEUCC/ Post-Diploma Programme 31  UNIT 1 TIME NEEDED FOR TECHNOLOGY SESSION 6 DEVELOPMENT Perhaps the most amazing feature of our planet is its rich diversity of life. Millions of beautiful and intriguing species populate the earth and help sustain a habitable environment. This vast multitude of life creates complex interrelated communities where towering trees and huge animals, live together with and depend upon, such tiny life-forms as viruses, bacteria and fungi. Together, all these organisms make up delightfully diverse, self-sustaining communities, including dense, moist forests; vast, sunny savannas; and richly colorful coral reefs. From time to time, we should pause to remember that, in spite of the challenges and complications of life on Earth, we are incredibly lucky to be here. We should ask ourselves; what is our proper place in nature? What ought we to do and what can we do to protect the irreplaceable habitat that produced and supports us? These are some of the central questions of environmental science. 6.4 What Is Environmental Science? We inhabit two worlds. One is the natural world of plants, animals, soils, air, and water that preceded us by billions of years and of which we are a part. The other is the world of social institutions and artifacts that we create for ourselves using science, technology, and political organization. Both worlds are essential to our lives, but integrating them successfully causes enduring tensions. Environment (from the French environner: to encircle or surround) can be defined as (1) the circumstances and conditions that surround an organism or group of organisms, or (2) the social and cultural conditions that affect an individual or community. Since humans inhabit the natural world as well as the “built” or technological, social and cultural world, all constitute important parts of our environment. Environmental science is the systematic study of our environment and our place in it. A relatively new field, environmental science is highly interdisciplinary. It integrates information from biology, chemistry, geography, agriculture, and may other fields. To apply this information to improve the ways we treat our world, environmental scientists also incorporate knowledge of social organization, politics, and the humanities. In other words, an environmental science is inclusive and holistic. Environmental science is also mission-oriented; it implies that we all have a responsibility to get involved and try to do something about the problems we have created. 32 CoDEUCC/ Post-Diploma Programme  UNIT 1 INTRODUCTION TO CHEMICAL SCIENCES SESSION 6 As distinguished economist Barbara Ward pointed out, for an increasing number of environmental issues, the difficulty is not to identify remedies. Remedies are now well understood; the problems is to make them socially, economically, and politically acceptable. Foresters know how to plant trees. But not how to establish conditions under which villagers in developing countries can manage plantations for themselves. Engineers know how to control pollution, but not how to persuade factories to install the necessary equipment. City planners know how to build housing and design safe drinking water systems, but not how to make them affordable for the poorest members of society. The solutions to these problems increasingly involve human social systems as well as natural science. Criteria for environmental literacy have been suggested by the National Environmental Education Advancement Project in Wisconsin. These criteria include awareness and appreciation of the natural and built environment, knowledge of natural systems and ecological concepts, understanding of current environmental issues, and the ability to use analytical and problem-solving skills on environmental issues. These are good goals to keep in mind as you study this book. Self-Assessment Questions Exercise 1.6 1. Why do technological developments often take much time? 2. What are CFC’s. 3. Why didn’t scientists realize the fate of CFC’s in the atmosphere that early? 4. What is technology? CoDEUCC/ Post-Diploma Programme 33