Once you get this book in your hand, a number of questions will be raised in your minds–What is chemistry? Why should we learn chemistry? How will we be benefited from chemistry? Does it have any relation to other branches of science?–We shall learn the answers to these questions in this chapter.
|By the end of the lesson, we will be able to:|
· explain the concepts of chemistry
· identify the scropes of chemistry
· explain the relation of chemistry to the other sciences
· explain the importance of learning chemistry
· describe the methods of investigation and research in chemistry
· plan types of investigative taskes, choose hypothesis and conduct experiments
· take necessary safety measure while experimenting practically
· explain the phenomenon of natural and physical world in terms of chemistry
- Introduction to chemistry
Natural science is one of the branches of science. Understanding aspects of nature by means of logic, observation or expreimentation, explaining them and producing hypothesis about them are the areas of natural science. Chemistry is one of the branches of natural science that discusses structure of matter, their nature and changes. For example, coal contains carbon. Chemistry discusses how the carbon atoms reside in coal and how these atoms react with oxygen in air when burnt and how they produce heat. All matters including animals and objects are its subject. Natural science has branches like physics, chemistry, botany, zoology, microbiology, astronomy, soil science etc. What is there in your food and how they are there is discused in chemistry. Again, think of the new cycle you bought. After some days, the iron parts of the cycle started to get rust on them. Chemistry discusses that too. Chemistry started with the creation of this world. But it is probably the moment when the first man built a fire striking two stones that man started to have their control on chemistry. From the prehistoric age, humans have used chemistry when they refined metals, made earthen utensils burning soil, prepared medicines and perfumes taking extracts and juices from trees and plants. So far, we know that the first metal human beings used is gold. Besides, they have also used metals like copper, tin, silver etc.
Human learned to melt copper and tin, mix them and cool the mixture into another hard alloy named bronze at around 3500 BC. Bronze was used to make quality weapons. These were used by the people to hunt animals, cultivate crops, cut fire wood etc. This alloy became an essential product of the then human race. Bronze cntributed a lot to the progress of human civilization.
The ancient philosophers used to think a lot about structure of matters. The Greek philosopher Democritus declared in 380 BC that, a small particle will be available at a stage when we synthesize any metall. This prticle is indivisible and he called it atom. Some Indian philosophers of the age also had similar views. But none of these ideas had a practical base. Aristotle opposed this idea.
He along with another school of philosophers believed all matters are made of soil, fire, water and wind. That is why humans did not accept the idea of atom for quite a long time.
In the mediaeval age, someArab Muslim philosophers tried to make gold out of cheaper materials like copper, tinand lead.They also tried to get an elixir which would lengthen the life of humans.Though they failed in their original attempts yet they wrote down their experiments. Basically, these were the earliest attempts of systematic study of chemistry or experimentation.These mediaeval Arab experimentation with chemistry was called Alchemy and the philosophers were known as Alchemists. The term Alchemy comes from the Arabic word Al-Chimia which again takes its origin from Chemi or Kimi. The word chemistry comes from this chemi. Alchemist Jabir AI Hiyan is the frrst scientist to hold chemical experiment in a laboratory.That is why he is sometimes called the father of chemistry. Jabir al Hiyan believed all matters are composed of four components- soil, fire, water and wind Therefore, although experimented, Jabir was not very clear about the mysteries of chemistry.Scientists including Antony Lavorsiere, Robert Boyle, Sir Francis Bacon and John Dalton are the first school to start experimenting with chemistry understanding the real spirit of this science. Antony Lavorsiere is called the father of modern chemistry.
Table 1.01: Explanation of different incidents in terms of chemistry.
|A green mango is sour while a ripened mango is sweet||There remain various organic acids like succinic acid, malloic acid etc. in a green mango which makes it sour. As it ripens, these acids transform into glucose and fructose in chemical reactions and turns the mango sweet.|
|Burning of kerosene, natural gas and wax||The main component of these elements is hydrocarbon which is a composite form of carbon and hydrogen. When we burn them, carbon and hydrogen react with oxygen of air and produce carbon-di-oxide, vapour and heat.|
|Taking antacid due to acidity in stomach||Acidity occurs in the stomach when excess hydrochloric|
acid is generated inside. Antacid contains aluminum hydroxide and magnesium hydroxide. These two compounds neutralize hydrochloric acid.
These incidents are sufficient to tell you that our life is irrevocably related to chemistry. Therefore, chemistry is one of the important branches of science.
1.2 The Scopes of Chemistry
Wherever there is element, there is chemistry. Various gaseous elements are there in the air. There are continuous chemical changes occurring in the air. The same is there in the soil we are living on. It is happening now, it happened in the ancient days too. The earth was highly heated at the moment of its creation. There was no wind, nor any animal. It took millions of years of chemical reactions for the creation of atmosphere, water and thousands of other elements.
These altogether contributed to the habitability of the earth for animals. All
animals including human beings, microscopic lives like bacteria, amoeba, huge trees and animals have bodies which contain various kinds of chemicals. Each body is a kind of chemical factory where chemical reactions are taking place every moment. We live because of these chemical reactions. Again, with the advent of civilization, humans have produced various necessary items and products by means of chemical reactions and put them to their use. For example, the dresses you put on, the paste you brush your teeth with, the comb you fix your hair with, the cosmetics you use on your skin- all are chemical products. Besides, soap, toilet cleaner, life saving drugs, all are chemicals too. We use fertilizers and insecticides in our field crops, use petrol, diesel etc. in vehicles. These are industrial products made out of chemical reactions. In fact, the scope of Chemistry is so vast that it cannot be summarized easily. The table below tries to present some of the scopes in brief:
Table 1.02: Some scopes of chemistry.
|Substance||Element||Source and Chemical Change|
|Air||Mostly oxygen||When we inhale air, the oxygen in it reacts with the food substances inside our body and produces energy.|
Hydrogen, oxygen and mineral salts
Water plays a role in the chemical reactions that take place inside our body. It also works as solvent of various substances in the body. The poisonous substances in the body mix with water and come out in the form of urine and sweat. Mineral salts such as calcium, magnesium etc. play a vital role for our body.
|Fertilizer||Nitrogen, oxygen, carbon, phosphorous,calcium, magnesmm, potassium etc.||The elements are highly necessary for plants. Different fertilizers contain compounds of these substances. As a result, these fertilizers act asnutrients and help get a good crop.|
|Paper||Cellulose||Paper is one of the most significant inventions of human civilization. Bamboo, the outer skin of sugarcane etc. contain huge amounts of cellulose. The paper mills turn these sources into paper by means of chemical reaction.|
1.3 Relationship Between Chemistry and Other Branches of Science
There are various branches of science like chemistry, biology, physics, mathematics, environmental science, soil science etc. Each of these branches is related to the other branches. Very much like the other branches are related to chemistry, so is chemistry related to the other branches. Let us now check the relationship with some examples.
Relationship with Biology: All plants produce glucose on their green parts in the photosynthesis process. Photosynthesis is basically a chemical process. Plants take in carbon-di-oxide from air and water from the soil. Then it uses the chlorophyll of its green parts to produce glucose in the reaction between water and carbon dioxide. Animal bodies synthesize the proteins of animal’s intake and produce glucose, amino acid etc. All animal bodies are indeed stuffed with various chemicals. Biology discusses these chemicals and chemical reactions that take place inside the bodies of plants and animals. That is where the two sciences are interrelated
Relationship with Physics: Physics discusses magnet, electricity, different machines etc. Battery used for getting electricity is contribution of chemistry. Energy gleaned by burning oil, gas or coal is the source for vehicles and electricity. Chemistry is also dependent on physics. Physical chemistry is a branch of chemistry, the theories of which are essentially dependent on theories and formulas of physics.
Relationship with Mathematics: Mathematics has a close relationship with chemistry. Mathematical theories and formulas act as the base of all formulas and measurements of chemistry.
In the same way, chemistry is directly and indirectly related to the other branches of science too.
1.4 The Importance of Studying Chemistry
Imagine what happens on a typical day with you. You use toothpaste, once you get up from bed in the morning. Then you start reading your books. Your mother serves you biscuits and tea. After finishing that, you take your bath. When you enter the washroom, you find it a bit unclean. You use toilet cleaner to clean it and then have bath using scented soap and shampoo. You use lotions after bath. Then you take your breakfast and go to school. The teacher there uses chalk on the board to simplify your lessons. Now, do you see, all the things you are using, e.g. paste, biscuit, tea, toilet cleaner, soap, shampoo, chalk etc. are contributions of chemistry.
Not only that, we use fertilizers to increase fertility of fields, use insecticides to keep away insects from our crops, preservatives to store the food for a longer time. This way, the whole process of food and cultivation is dependent on chemistry.
Today, cholera, typhoid, tuberculosis etc. are curable diseases but they were once killer diseases. Millions of people died of them in the ancient days. Humans have invented cures for them by means of their knowledge of chemistry. Nowadays, the field of medicine has developed so much that many people are cured of different cancers too.
Chemical wastes from industries, vehicles, consumer products etc. are doing harm to our environment. These contain carbon dioxide, carbon monoxide, sulphur dioxide, various acids, heavy metals like mercury, lead, arsenic, cobalt etc. When they come in contact with air, air is polluted, when they come in touch with water, water gets polluted. They enter human bodies and harm them. Again, use of excess chemicals is harmful for us. Insecticides help us save our crops but excess insecticide gets washed away to the water bodies, polluting the water.
Some of it gets vaporized and pollute the air. Chemistry tells you all these natural and life oriented facts.
By now you should have understood that chemistry plays a significant role in our advancement but excess of it is harmful for us and nature as well. Many diseases are still there which do not have cures. Our duty is to study chemistry and try inventing those drugs. Therefore, learning chemistry does not only benefit us by means of newer inventions, it also helps us realize how we are harming our nature. Your learning chemistry will take the world steps ahead. That is our expectation.
1.5 The Process of Research in Chemistry
The aim of science is the betterment of humanity. Scientists are constantly working with the same aim in their minds. The term scientist certainly rings the names of great scientists like Einstein, Newton, Archimedes, Lavoisier, Galileo etc. They are obviously great scientists. However, the meaning of the term scientist has the scope for you too to be called so. Indeed, science is that knowledge which is gleaned out of systematic experimentation. The process to glean knowledge by experimenting is known as research. One who carries out such research is a scientist.
Therefore, if you carry out research, you can also be a scientist. Experimenting through a perfect and systematic process in order to learn something is called research. It means, there is a certain procedure to carry out a research. Research in chemistry also follows some procedure. Now we shall learn the steps of this procedure.
In the first step of a research, you need to determine what you want to learn or what new thing you want to invent. Suppose, you want to learn whether heat will be produced or absorbed as ammonium chloride is dissolved in water. This is known as topic selection.
In the second step, you have to investigate the matter. At this stage, you will read some books or some papers from the internet and other sources in order to learn
how such kind of an experiment was carried out by someone else and what result it did yield. Suppose, you have learned that another chemical compound calcium oxide, when dissolved in water, produces heat. You will also be able to learn what kind of apparatus, chemicals and steps were followed in this experiment. That will give you an idea about what things you will require to conduct the test yourself. Besides, you will have an idea about the probable result-in this case, if you dissolve ammonium chloride in water, heat will be produced.
Again, you will be able to decide what kind of materials you are going to use and what will be the steps of the experiment. You came to know that you would need a beaker, water, ammonium chloride, thermometer, glass rod, balance etc. Firstyou will take water in the beaker. You will record the temperature of the water in the beaker with the thermometer. Then, you will weigh ammonium chloride using the balance and mix and dissolve that with the glass rod in the water, a number of times. Each time, you need to check the temperature of water. This is the procedure of your experiment. Now you can start your experiment.
|Quantity of dissolved ammonium chloride in water of beaker||Temperature of the solution|
|Og (nothing dissolved)||25°C|
|15 g||10° C|
Take 250 mL water in the beaker and check the temperature. Suppose, the present temperature is 25°C. Record it in your notebook. Now, with the help of the balance, weigh 5g ammonium chloride and mix it in the water. Use the glass rod to stir so that it gets dissolved. As soon as the chemical is dissolved, measure and record the temperature. Now the temperature is 20°C. Add, mix and dissolve another 5g of ammonium chloride in the beaker. See what the temperature is with 10g chemical in the water. Follow the same procedure again. Now the beakers water has 15g of dissolved ammonium chloride and let’s suppose the temperature is 10°C. Record the data in your notebook.
If you analyze the data shown above, you will see, the more ammonium chloride is dissolved in water, the less the temperature of water becomes. You will decide, since dissolving ammonium chloride in water decreases the temperature of water, ammonium chloride absorbs heat from water in order to get dissolved. The result is dissolving ammonium chloride in water results in absorption of temperature. The steps followed by you in the above experiment can be shown in the following flowchart:
Whenever you are dealing with some research in chemistry, you are required to follow the same steps.
1.6 Safety Measures in Chemistry Laboratory and in use of Chemicals.
The place where scientific experiments are held is called the laboratory. Similarly, the place where experiments of chemistry are held is called Chemistry laboratory. It is understood, there will be various chemicals in a chemistry laboratory. Almost all chemicals are harmful to some extent for us as well as our environment. Some chemicals are prone to explosion, some are flammable, some harm our body directly and some are dangerous for nature. Most of the apparatus in a chemistry laboratory are made of glass. Therefore, we need to be cautious from the moment of entry into the laboratory to the moment we come out. Lack of caution may result in accidents, e.g. if acid falls on your body, you will get injured; if acid falls on your dress, the dress will be spoiled. Besides, there may be accidents including fire or explosion in a laboratory. Therefore,
you need to wear an apron. The apron will be knee-long and the sleeveswill be up to yam wrist. Its colour will be white.You will usc hand gloves and safety goggles on your eyes. Some of these safety measures are given inthe following picture.
We need to learn the nature of a chemical before we start to use it. We need to know whe1her that is tlannnable or Radio-active. These are made clear using some signs on the containers. To introduce a globally harmonized system about this, the United Nations Organized a conference named Environment and Development. This conference gave a set of harmonized signs for different risky substances and their level of risk. The table below contains some signs and their explamations identifying risk, extent of risk and precautions.
Table-1.04: Signs and their explanations identifying risk.
|Sign||Risk, Exteat of riak ud preeuation|
|Explosive substance||Weneed tobe very careful about these substances. We must keep in mind that friction and fire may cause serious explosion from these which will be harmful for our body as well as the laboratory. We need extreme caution in handling these. TNT, organic peroxide, nitroglycerine etc. are such kind of substances.|
|Flammable substance||Alcohol, ether etc. are flammable. These may catch fire quickly. Therefore, we need to keep them away from fire or heat.|
|Toxic substance||Substances with this sign are poisonous. If we come in touch with them or inhale them, they may cause harm to our body. Benzene, chlorobenzene, methanol. etc. are such substances.We must wear apron, hand gloves and safety goggles when handling them.|
|Irritant substance||Cement dust, light acids, base, nitrous oxide etc.cause irrition on skin. eyes and breathing system. We must wear aprons, hand gloves and safety goggles when handling them.|
|Hazardous substance||Direct contact on skin or inhalation of such substances may cause short or long term harm to our health. They may affect our breathing system or even cause diseases like cancer. Benzene, toluene, xylene are such substance. We must wear aprons, hand gloves and safety goggles when handling them.|
|Radioactive substuce||These substances emit hannfu1 rays which may cause diseases like cancer or disable somebody. We need to be extremely cautious in handling these. Uranium, radium etc. are of this kind.|
|Substances with this sign are dangerous for the environment, meaning, they harm both animals and plants. They require caution when in use. Again, they have to be gathered ina place after use. They have to be recycled as much as possible. That way, they cannot do much harm to the enviromnent.|
|Corrosive||These cause injury to body in contact. Inhalation of such substances may cause injury inside the body. Hydrochloric acid, sulfuric acid etc. arc examples of this kind.|
Multiple Choice Questions.
1. Which of the following substances is used for preserving processed food fur a long time?
a. preservative b. vinegar c. ethylene d. acetylene
a. explosive substance b. flammable substance c. radioactive substance d. flame of fire
3. Which of the following signs indicate a radioactive substance?
4. Which of the following metals is melted and mixed with copper to priduce bronze?
a. iron b. zinc c. tin d. lead
a. What is research?
b. Why does ripe mango taste sweet?
c. How is the figure-A relation to chemistry–explain.
d. Which of the activities of the stem, when done in excess, is harmful for th environment–answer with reasons.
a. What is chemitry?
b. Why do we take antacid for acidity in the stomach?
c. The substance containing sign-3 harmful for human beings–explain.
d. Chemical substance containing sign-1 and sign-2 are risky when in use-explain.