Oasis School Science and Technology 10 New

Oasis School Science and Technology - 10 401 Manufacturing of Ammonia Gas Manufacturing of ammonia gas for commercial purposes is carried out by applying Haber's process. In this process, a mixture of a 3:1 ratio of hydrogen and nitrogen gases is heated strongly at about 500°C temperature and 200 to 500 atmospheric pressure. To speed up this reaction, we use an iron catalyst and a molybdenum promoter of the catalyst. N2 + 3H2 500 0 C/200 to 500 atm. Fe (catalyst) and Mo (promoter) 2NH3 Necessary conditions for Haber's process i. We should maintain 500°C temperature and 200 to 500 atmospheric pressure. ii. Powdered iron as a catalyst and molybdenum as a promoter of a catalyst should be used. iii. We should use a high concentration of nitrogen and hydrogen gases. Properties of Ammonia Gas Physical properties i. Ammonia is colourless and tasteless gas with a pungent smell. ii. It is basic, so it turns red litmus paper into blue. iii. It is lighter than air. Its atomic mass is 17 whereas the molecular mass of nitrogen gas which makes up 78% of the atmosphere is 28 amu and the molecular mass of oxygen which makes up 21% of the atmosphere is 32 amu. So it rises in the air. iv. It is highly soluble in water to give ammonium hydroxide (NH4 OH). v. It is non-combustible in nature. vi. Ammonia gas becomes liquid at -33.4°C and freezes at -78°C. Chemical properties 1. Reaction with water Ammonia is highly soluble in water to give ammonium hydroxide. The resultant solution of ammonium hydroxide is basic. NH3 + H2 O NH4 OH (Ammonium hydroxide) The solution of ammonium hydroxide, which is produced above shows the basic nature. Therefore, it reacts with an acid to give salt and water. For example; when the above solution reacts with hydrochloric acid, it gives ammonium chloride and water. NH4 OH + HCl NH4 Cl + H2 O 2. Reaction with acids Fact File Molybdenum used during laboratory preparation of ammonia gas is called promoter because it makes the catalyst more active.

402 Oasis School Science and Technology - 10 Ammonia gas is basic. So, when it is treated with acids, it gives salts. For example, ammonia gives ammonium chloride with hydrochloric acid. NH3 + HCl NH4 Cl Ammonia gives ammonium sulphate with sulphuric acid. 2NH3 + H2 SO4 (NH4 )2 SO4 3. Reaction with carbon dioxide (CO2 ) Ammonia reacts with carbon dioxide to give urea. This reaction is carried out at about 1500°C temperature and under certain pressure. Ammonia + Carbon dioxide 1500°C NH2 CONH2 + H2 O 2NH3 + CO2 1500°C NH2 CONH2 + H2 O 4. Combustibility Ammonia is a non-combustible gas. Besides, it does not support combustion, but it burns with oxygen to give nitrogen and water. 4NH3 + 3O2 2N2 + 6H2 O 5. When ammonia is heated with oxygen in the presence of the platinum catalyst, it produces nitrogen oxide. 4NH3 + 5O2 2NO + 6H2 O Uses of ammonia gas i. Ammonia is used in manufacturing nitrogenous fertilizers like urea, ammonium phosphate, ammonium sulphate, etc. ii. Liquid ammonia is used as a cooling agent in the refrigerator. iii. It is used in manufacturing different types of industrial chemicals nitric acid, plastics, fibres, colours, dyes, etc. iv. It is used as a cleaning agent to remove oil, grease, fat, etc. v. It is used to develop a blueprint of a map. vi. It is used as a laboratory reagent to make different types of chemical compounds. Reasonable Fact Phenolphthalein does not turn pink when it is mixed with the mixture of kerosene and ammonia. Kerosene does not form ammonium hydroxide with ammonia and does not give the pink colour within a round bottom flask.

Oasis School Science and Technology - 10 403 Activity 1 Objective To show that ammonia is highly soluble in water and basic in nature. Materials required Round bottom flask, water trough, stand, phenolphthalein, etc. Procedure We take a round bottom flask containing freshly prepared ammonia gas. It is fitted with a delivery tube. The lower end of the delivery tube should be inserted within the water of a water trough, which has some drops of a phenolphthalein indicator, and the upper end is within the round bottom flask. As a result, the delivery tube carries a jet inside the round Stand "bottom flask. As ammonia gas cools down inside the round bottom flask, it creates low pressure inside it. Due to the difference in the pressure of the round bottom flask and the water of the water trough, some drops of water rise in the flask and form ammonium hydroxide. The formation of ammonium hydroxide creates a vacuum inside a round bottom flask. We know that ammonium hydroxide is basic in nature so it changes the colour of phenolphthalein to pink. As the process continues, it creates more vacuum inside the round bottom flask. Hence, water rushes up with high pressure to fill the vacuum like a fountain. Now the whole flask also becomes pink in colour. Conclusion The above activity demonstrates that ammonia dissolves strongly in water to produce, a base, ammonium hydroxide. NH3 Round bottom flask Water Stand Greenhouse A natural or artificial set-up that can trap heat energy and regulate the temperature of a particular place keeping greenery of the plants is called a greenhouse. It could be the earth itself as a natural greenhouse or a manmade one. Greenhouse Effect Different types of gases like carbon dioxide, chlorofluorocarbon, methane, oxides of nitrogen, water vapour, etc. are present in the troposphere of the atmosphere. These gases cover the earth's surface making a dense canopy similar to the glass frame of an artificial greenhouse. The dense canopy of different gases allows solar radiation to enter the earth's surface but does not allow it to escape after reflection. As a result, these solar radiations are absorbed in the atmosphere, increasing the temperature of the earth. The phenomenon of increasing the temperature of the earth as in an artificial greenhouse is called the greenhouse effect. The gases which are responsible for the greenhouse effect are called greenhouse gases. Environmental scientists estimated that carbon dioxide had a 57% impact on the greenhouse effect, chlorofluorocarbon had 25%, methane had 12% and oxides of nitrogen were 6%. The temperature of the earth is increasing gradually

404 Oasis School Science and Technology - 10 due to the greenhouse effect. This process is called global warming. Global warming is causing melting of ice mass in the polar ice caps increasing the sea level. Increasing sea level results inundation of islands and flooding in coastal areas affecting lives of million peoples. Increased temperature also melts the mountain ice caps and glacier resulting glacial lake outburst flood impacting lives of downstream people. The high temperature also affects water cycle and biodiversity. It has numerous impacts in every sectors of human welfare. Reasonable Fact It is the atmosphere due to which we feel warm. It is the atmosphere due to which we feel warm because the atmosphere absorbs a large amount of heat from the sun and ground. Without the atmosphere, we would certainly die by being exposed to UV rays and below freezing temperature of the earth. The sources of greenhouse gases The greenhouse gases are released from different human activities as well as by some natural processes. Some of them are listed below: i. Carbon dioxide gas (CO2 ) is produced by the burning of fossil fuels like coal, oil, natural gases, etc. ii. Methane (CH4 ) is produced from the decomposition of domestic wastes and sewage. iii. Chlorofluorocarbon (CFC) is released from refrigerators, air conditioners, aerosol spray cans, etc. iv. Water vapour (H2 O) is released from the oxidation of organic compounds as well as the vaporization of water from water sources. Reasonable Fact Refrigerators, air conditions, deodorants etc. are not only bad for the ozone layer but also for greenhouse effect ? Refrigerators, air conditions, deodorants etc. are bad for the ozone layer as they release gases called Chlorofluorocarbons which deplete the ozone layer. But some of them contain ammonia and hydrofluorocarbons which do not deplete the ozone layer but contribute to increase the greenhouse effect. Earth: A Natural Greenhouse If we compare the earth and the moon, which are nearly at same distances from the sun, the earth has suitable temperature, but the moon is very cold and hot during the night and the day respectively. This is due to the reason that the moon doesn’t have an atmosphere. So it is not able to trap the solar rays inside it. But the earth is surrounded by several layers of gases called the atmosphere that traps the heat from the sun. But how? The answer is due to the greenhouse effect. Fig: Earth is a natural green house

Oasis School Science and Technology - 10 405 Reasonable Fact Earth acts as a natural greenhouse. Earth acts as a natural greenhouse because the atmosphere that covers the earth traps the solar heat inside. Artificial Greenhouse An artificial greenhouse is a structure with walls and roofs made chiefly of transparent materials such as glass or plastics in which plants requiring regulated climatic conditions are grown. A greenhouse is also called a glasshouse or a hothouse. The size of greenhouses ranges from small sheds to industrial-sized buildings. A miniature greenhouse is known as a cold frame. The interior of a greenhouse exposed to sunlight becomes significantly warmer than the external ambient temperature protecting its contents in cold weather. These houses allow the microwaves of sunlight to enter but do not allow them to escape after reflection. As a result, they convert solar energy into heat energy and the energy is stored inside the greenhouse. Ultimately, the temperature inside the greenhouse increases. The roof of the artificial greenhouse is slanted to allow more sunlight to enter. Reasonable Fact It is always warmer inside the greenhouse than the surrounding. It is always warmer inside the greenhouse than in the surroundings because the glass allows the short wave radiation from the sun enter through it while traps the reflected and re-emitted long wave radiations that produce heat. Greenhouses are used extensively by botanists, commercial plant growers, and gardeners. Particularly in cool climates, greenhouses are useful for growing and propagating plants because they both allow sunlight to enter and prevent heat from escaping. Reasonable Fact The roofs of the greenhouse can be of various shapes but mostly the slanted roof is preferred. The roofs of the greenhouse can be of various shapes but mostly the slanted roof is preferred because it allows maximum sun rays to enter even if the sun is too low on the horizon. Importance and Utilities of Artificial Greenhouse Greenhouses have more temperature than their surroundings. So, different plants like flowers, fruits, vegetables, etc. can be grown in the off-season. It helps to earn money. Plants that grow in hot places can be grown in cold places inside greenhouses. The importance and utilities of greenhouses are as follows. Fig. Artificial greenhouse Fact File A plastic tunnel in botanical gardens or agricultural fields is also an artificial greenhouse.

406 Oasis School Science and Technology - 10 i. It extends the growing season creating favourable environment to grow crops all round the year even in off-season. ii. It protects plants from harsh weather conditions such as wind, rain and hail. iii. It increases the production of crops as the crops get favourable environment for higher yield. iv. It reduces the chance of infection of crops by pest and diseases from outer environment. v. It conserves water by reducing runoff and evaporation. Importance of the greenhouse effect If there were no greenhouse gases in the atmosphere, all the solar radiation entering the earth's surface would escape into space. As a result, heat would not be stored on the earth. Consequently, the temperature of the earth would be less by 39°C than today's temperature. Ice would cover the earth and there would not be any organisms on the earth. So, the greenhouse effect is very important for the existence of lives on earth. Adverse impacts of the greenhouse effect Due to various human activities, the concentration of greenhouse gases is increasing day by day. It increases the temperature of the earth. The adverse consequences of the greenhouse effect are given below: 1. Effects on animals i. It helps to spread different types of diseases like malaria, filariasis, cholera, diarrhoea, etc. ii. It helps to increase the number of pathogenic insects. 2. Effects on plants i. It affects the water cycle, soil moisture and soil composition. As a result, there is a change in the cultivation and harvesting periods of crops. ii. Due to the effect of global warming, tropical plants are seen in the temperate region. iii. It helps in the breeding, growth and development of disease-causing insects. 3. Effects on climate i. It increases the temperature of the earth. ii. It brings the melting of ice in the polar region, which increases the sea level. As a result, low land areas of the earth may submerge. iii. It changes the pattern of rainfall and weather conditions. Ways of controlling the greenhouse effect The greenhouse effect can be controlled by the following methods: i. It can be controlled by decreasing deforestation and increasing afforestation. ii. It can be controlled by reducing the use of fossil fuels like petrol, diesel, kerosene, coal, etc. iii. It can be controlled by banning the production and use of CFCs. iv. It can be controlled by using solar energy, wind energy, biogas, etc.

Oasis School Science and Technology - 10 407 Acid Rain The rain that contains a small volume of acids formed by chemical reactions between rain and industrial gases is called acid rain. Its pH value ranges from 3 to 5. Simply, acid rain is rain or any other form of precipitation that is acidic in nature. It produces harmful effects on the environment and affects natural resources. It was first discovered in 1960. Cause of acid rain Air pollution is the major cause of acid rain. It is the result of human activities. When industrial gases like carbon dioxide, sulphur dioxide, nitrous oxide, etc. are released into the atmosphere, they undergo several chemical reactions and combine with rainwater. Then, they fall upon the animals, plants, soil etc. and affect them. The acids that mix with rain are hydrochloric acid (HCl), sulphuric acid (H2 SO4 ), nitric acid (HNO3 ), etc. The chemical reactions below show the formation of these acids from industrial gases. H2 O + CO2 H2 CO3 (Carbonic acid) 2SO2 + O2 2SO3 SO3 + H2 O H2 SO4 (Sulphuric acid) Effects of acid rain i. Acid rain corrodes the skin of animals and human beings and causes skin diseases. ii. It affects the growth and development of plants by making the soil acidic. iii. It increases the acidity of water and affects aquatic plants and animals. iv. It corrodes historical and architectural monuments like buildings, statues, arts, etc. v. It increases the acidity of land, kills microorganisms and decreases the fertility of the soil. vi. It damages the crops and decreases productivity. Control measures for acid rain i. Reducing the use of fossil fuels and promoting alternative and clean sources of energy. ii. Adopting techniques of reuse of emitted gases from industries. ii. Development of technology that controls the production of SO2 and CO2 . Activity 1 Discuss the major environmental problems occurring in your neighbourhood including their causes, effects and control or preventive measures. Reasonable Thinking Skill Reasonable Thinking Skill R T S 1. We do not use dilute sulphuric acid in place of dilute hydrochloric acid during the preparation of carbon dioxide. When dilute sulphuric acid reacts with calcium carbonate to form carbon dioxide gas, calcium sulphate is also formed.

408 Oasis School Science and Technology - 10 Dil. H2 SO4 + CaCO3 → CaSO4 + CO2 + H2 O Thus, formed calcium sulphate is insoluble in water. It deposits over calcium carbonate and covers it. It prevents further reaction. And hence the production of carbon dioxide will be stopped. 2. Study the given figure and answer the following questions. i. Why is dilute hydrochloric acid poured from the thistle funnel? Dilute hydrochloric acid is poured from the thistle funnel because it makes the supply of acid at a particular place easy and convenient. ii. Write the name of the solid present in that container. The solid used in the container is limestone (calcium carbonate). iii. Which gas is collected in the gas jar? Carbon dioxide is collected in the gas jar. 3. Huge cities are more likely to suffer from acid rain. Acid rain is a rainfall whose pH value is less than 7. Acid rain is formed when industrial gases dissolve with rainwater and form respective acids. Industrial gases are released from industries, factories, LPG gas and vehicles. These structures are more available in huge cities. So, the city sky has a huge quantity of industrial gas which can mix with rainfall to form acid rain. 4. Tropical insects are widely spreading to temperate regions. What has the greenhouse effect to do with it? The spread of tropical insects to the temperate region is an outcome of increase in temperature of the tropics. The greenhouse effect is a process in which heat energy is trapped by greenhouse gases, which increases the temperature of the environment. Due to increased greenhouse effect, the temperate region is getting hotter. As a result insects, germs, plants etc. from the tropical region are spreading to temperate and colder regions to find favourable climate for living. 5. Many farmers are growing tomatoes under plastic tunnels in Nepal. They have a good harvest despite unfavourable weather. How have plastic tunnels helped farmers? Despite unfavourable weather, farmers were able to get a good harvest when they grew tomatoes under the plastic tunnels. The plastic tunnels are useful for farmers in multiple ways. For example: i. It works as a greenhouse. Keeps the plants warm even at night and in winter. ii. It protects seedlings and plants from frost and snow. iii. It protects buds, flowers and fruits from wind and hail. iv. Crops and vegetables many grow weeks before the actual season getting high value for their products. . 6. Let’s suppose you became the Mayor of your city, what would you do to prevent acid rain? Let’s suppose I became the mayor of my city. I would do the following things to prevent acid rain: dil.HCl Gas

Oasis School Science and Technology - 10 409 i. First of all, I would replace the LPG gas stove with an electric induction heater in my city. ii. I would request everyone to use electrical devices over coal-powered devices. iii. I would plant more plants in any available area, footpath and parks in my city. iv. I would prevent the use of old vehicles in my city. v. I would request every industry and factory to resettle far away from the city. vi. I would introduce electric buses, electric trains and other electrical means of transportation in the city. vii. I would manage solid waste from the city properly. 7. Compare a natural greenhouse with an artificial greenhouse. The comparison between a natural greenhouse and an artificial greenhouse are: SN Natural greenhouse SN Artificial greenhouse 1 Earth itself is a natural greenhouse where solar radiation is trapped by the atmosphere. 1 An artificial greenhouse is a plastic or glass house where the temperature is regulated artificially. 2 It helps to keep the earth warm, regulate weather etc. 2 It helps to grow off-season herbs, flowers and vegetables. 8. Why is the hard glass test tube slightly slanted during the laboratory preparation of ammonia? The hard glass test tube is slightly slanted during laboratory preparation of ammonia gas so that water drops would flow down to the lower parts far away from the hot parts and chemicals. Slanting also helps to reduce steam pressure and prevent cracking of the test tube. 9. What happens when ammonia is mixed in water? Write its use. When ammonia is mixed with water it reacts to produce ammonium hydroxide. It is also called liquor ammonia. NH3 + H2 O → NH4 OH Liquor ammonia is used as a cleaning agent and emulsifier. Exercises 1. Choose the best answer from the given alternatives. a. Why is carbon dioxide called acidic gas? i. it dissolves in water to produce acetic acid. ii. it reacts with water to make carbonic acid. iii. it is sour. iv. it can neutralize a base b. What is the white cloud made of, which is formed when a drop of hydrochloric acid is dropped in a gas jar full of ammonia gas? i. cloud of carbon monoxide ii. fumes of sulphuric acid iii. fumes of ammonium chloride iv. clouds of water vapour c. What is the molecular formula of liquor ammonia? i. NH3 ii. NH4 ⁺

410 Oasis School Science and Technology - 10 iii. NH4 OH iv. NH4 CI d. Why is carbon dioxide found in deep wells and mines? i. it is lighter than the air ii. it is heavier than the air iii. it is insoluble in air iv. it is slightly soluble in air e. Which gas is mainly responsible for the greenhouse effect? i. carbon dioxide ii. oxygen iii. nitrogen iv. hydrogen 2. Define the following terms with required examples. a. Haber’s process b. Dry ice c. Fire extinguisher d. Greenhouse gases e. Greenhouse f. Greenhouse effect g. Artificial greenhouse h. Acid rain 3. Answer the following questions in very short. a. Write the name of two solids that reacts to produce ammonia in the laboratory. b. What is the objective of the lime tower during the preparation of ammonia in the laboratory? c. What are the required conditions for Haber’s process? d. What reacts to produce carbon dioxide in a fire extinguisher? e. What is the primary cause of the rise in sea level? f. What are the sources of carbon dioxide in the atmosphere? g. In which ratio ammonium chloride and calcium hydroxide are mixed during laboratory preparation of ammonia gas? h. What can be done to produce carbon dioxide in a larger quantity? i. What should be done to produce a large quantity of ammonia? 4. Give reasons. a. CO2 is collected by an upward displacement of air. b. A burning match stick extinguishes when CO2 , is passed over it. c. Lime water becomes milky white when CO2 is passed through it. d. Generally, CO2 is found in lower places like caves, mines, deep well, etc. e. A glass vessel is used to keep sulphuric acid inside a fire extinguisher. f. Ammonia gas is collected in an inverted gas jar. g. Moist red litmus paper is taken near the mouth of a gas jar to test carbon dioxide. h. Ammonia is a compound gas. i. Ammonia is called a basic gas but carbon dioxide is called acidic gas. j. Dry ice is used to store vegetables. k. We should reduce the use of fossil fuels. l. Carbon dioxide is called a greenhouse gas. m. Artificial greenhouse is used to farm off seasonal vegetables. n. It is warmer inside the greenhouse than in the surrounding. o. Over-greenhouse effect is a threat to the earth. p. The roof of the artificial greenhouse is slanted. q. Acid rain can corrode stone monuments.

Oasis School Science and Technology - 10 411 r. Anhydrous calcium chloride and phosphorus pentachloride are not used to remove moisture from ammonia. s. Cloudy days are warmer than the clear sky in winter. 5. Differentiate between the following. a. Carbon dioxide and ammonia b. Natural greenhouse and artificial greenhouse 6. Answer the following questions in short. a. Write the principle of laboratory preparation of carbon dioxide gas with a balanced chemical equation and draw a well-labelled diagram. b. Write the principle of laboratory preparation of ammonia gas. c. How can we test if the gas in the jar is ammonia? d. How can we test if the gas in the jar is carbon dioxide? e. Discuss the precautions for preparing ammonia gas in the lab. f. What are the precautions while preparing carbon dioxide gas in the lab? g. How does carbon dioxide react with the water? h. What happens when hydrochloric acid is introduced into ammonia gas? i. What can we do to minimize the over-greenhouse effect? j. Enlist the major effects of the greenhouse effect. k. How is acid rain formed? Explain with two reactions. l. Which gas is used in the refrigerator? Why? m. What is the importance of the earth as a natural greenhouse? n. What would happen if the earth stops working as a natural greenhouse? o. How is carbon dioxide collected during laboratory preparation? p. Enlist the effects of greenhouse effects. 7. Answer the following questions on the basis of the given figure. i. What is the primary objective of this structure? ii. Why is it warm inside this structure? iii. Why is the roof slanted in this structure? 8. Answer the following questions. a. Describe the laboratory preparation of ammonia gas. b. Describe the laboratory preparation of carbon dioxide gas. c. What are the conditions required for Haber’s process? Describe Haber’s process of industrial preparation of ammonia. d. How is urea produced from ammonia and carbon dioxide? Write with a chemical reaction. e. Write common uses of ammonia gas. f. How is carbon dioxide used in our daily life? g. What happens when? Give a balanced chemical equation. i. When ammonia reacts with carbon dioxide. ii. When ammonia reacts with water. iii. When ammonia reacts with sulphuric acid.

412 Oasis School Science and Technology - 10 iv. Ammonium sulphate is warmed with sodium hydroxide. v. A glass rod dipped in hydrochloric acid is introduced in a gas jar that contains ammonia. vi. When carbon dioxide reacts with sodium hydroxide vii. Carbon dioxide is passed through limewater for a short duration h. What are the physical properties of carbon dioxide and ammonia? i. What are the primary sources of greenhouse gases? j. What is the importance of greenhouses in our daily life? k. What are the causes of acid rain? Write any four. Also, mention its remedies. l. Answer the following questions after observing the given figure of laboratory preparation of ammonia. i. Write the principle of laboratory preparation of this gas. ii. Write the name of the solids present in the hard glass test tube. iii. How is the gas tested? iv. Why is the gas collected by the downward displacement of air? v. Which litmus paper is used to test this gas? m. Answer the following questions based on the given diagram. i. Which gas is being collected in the gas jar? ii. Write the equation for the reaction that occurs in Woulfe's bottle. iii. What happens when this gas is passed through lime water for a while? iv. Which litmus paper is used to test this gas? v. Why is this gas collected in an erect gas jar? n. Answer the following questions based on the given diagram. i. What is the name of chemicals A and B? ii. What happens when the seal is broken in the above device? Write the chemical equation. iii. What is the use of this device? dil.HCl Woulfe’s bottle Pieces of CaCO3 Delivery tube

Oasis School Science and Technology - 10 413 Key terms and terminologies 1. Metals : The electro-positive element which are good conductors of heat and electricity are called metals. 2. Minerals : Minerals are those naturally occurring chemical substances which contain metals more or less in amount. 3. Ores : Those minerals from which metals can be extracted conveniently and profitably are called ores. 4. Metallurgy : Metallurgy is the process by which we can get pure metals from their ores. 5. Mining : Mining is a process in which ores of various metals are taken out from the earth crust. 6. Calcination : The process in which carbonate and hydroxide ores are heated strongly with a limited supply of air is called calcination. 7. Roasting : The sulphide ores are heated strongly in excess supply of air is called roasting. 8. Ores of Iron : Haematite, Magnetite, Siderite , Limonite and Iron pyrite 9. Ores of Aluminium : Bauxite, Cryolite and Felspar 10. Ores of Copper : Copper pyrite or chalcopyrite, Cuprite, Chalcocite or Copper glance, Malachite and Azurite. 11. Ores of Silver : Argentite or silver glance, Horn silver, Silver copper glance and Ruby silver or pyrolite. UNIT 17 METALS Estimated teaching periods Theory 4 Practical 1 • Metals: concept of minerals and ores • Names of chief ores of iron, copper, silver and aluminium • Metallurgy: mining, grinding, concentration, smelting, roasting and electro refining (without chemical equations) The Sequence of Curriculum Issued by CDC Georgius Agricola is called the father of metallurgy or mineralogy because of his research and development of complex processes of mining metal ores, metal extraction and metallurgy of that time. He was born in the Roman empireon 13th June 1494 and died on 21st November 1555. He was a German Humanist scholar, mineralogist and metallurgist. He published over 40 complete scholarly works during his professional life on a wide range of subjects and disciplines, such as pedagogy, medicine, metrology, pharmacy, philosophy, etc. About the Scientist Georgius Agricola

414 Oasis School Science and Technology - 10 Introduction Do you know gold, silver, iron, copper, magnesium, calcium, etc.? What are they? They are the examples of metal. Most metals are found in nature either in a free form or in the form of different compounds. Most of the metals are highly reactive in nature, so are found in different types of compounds. Gold and platinum are less reactive metals; hence appear freely in nature. Metals are good conductors of heat and electricity that is why electric wires are made from copper, aluminium and other metals. Gold and silver are used to make different types of ornaments. Metals are very useful electro-positive elements which are used in every field of our life. More than 92 metals are present in the periodic table. Metals are very reactive elements, so except some metals (like gold, platinum, etc.) most of them are present in different types of compounds. These compounds are called mineral. From some minerals, we can take out metals by applying several extraction methods. The pure metals which are obtained by metallurgical process are used for different purpose. Gold and silver are used to make ornaments. Copper and aluminium are used to make electric wires. Iron, copper, aluminium and other metals are used by different constructional processes. Almost all metals are solid at the room temperature except mercury, gallium and cesium. Mercury is used in the thermometer as a thermometric substance and cesium is used in the solar panel. Metals Do you know gold, silver, copper, iron, aluminium, etc? What are they? They are some examples of metals. All these metals are electro-positive in nature; it means they lose electrons during the chemical combination. They are good conductor of heat and electricity. Hence, they are used to make electric wires. Thus, the electro-positive element which are good conductors of heat and electricity are called metals. Sodium, potassium, magnesium, aluminium, calcium, iron, cobalt, nickel, copper, gold, silver, zinc, barium, radium, beryllium, etc. are some examples of metals. General properties of metals Physical properties i. They are generally good conductor of heat and electricity as they have free electrons. ii. They are malleable in nature; it means that metals can be converted into very thin sheets after hammering. iii. They are ductile in nature; it means that metals can be drawn into thin and long wires after heating. iv. Freshly cut metals possess a brilliant metallic lustre. Fig: physical properties of metal

Oasis School Science and Technology - 10 415 v. Generally metals are hard in nature except lithium, sodium and potassium. vi. Metals are solid at the room temperature except mercury, cesium and gallium. vii. They have high density (or specific gravity). viii. They make a homogeneous mixture with other metals called alloy. ix. They dissolve only by a chemical reaction. x. They have a high melting and boiling point except mercury, sodium and potassium. xi. They are sonorous in nature. Chemical properties i. Most of the metal oxides are basic in nature. For example; Na2 O, CaO, MgO, etc. ii. They form unstable hydride compounds. For example: NaH, CaH2 , MgH2 etc. iii. Most metals when react with dilute acids give hydrogen gas. iv. Metals are good reducing agents. It means they easily combine with oxygen. Minerals In nature, there are so many chemical substances which contain metals in more or less amounts along with other substances. These naturally occurring earthen substances are called minerals. All minerals are unique. They have their own molecular formula. If minerals contain a large amount of metals, they are utilized to take out metals. So, minerals are naturally found earthy substances which contain metals more or less in amount. Mostly minerals are inorganic, solid, crystalline substances. Ores On the earth's crust there are large numbers of minerals which contain metals more or less in amount. All these minerals are not used to take out metals for commercial purposes. Those minerals which contain a large amount of metals are called ores. So, ores are those minerals which are used to extract metals for commercial purposes. Reasonable Fact All minerals are not ores but all ores are minerals. This is because all minerals contain metals more or less in amount but those minerals which contain metals more in amount and used to extract metals for commercial purpose are called ores. Metallurgy We know that most of the metals are found in different types of compounds. Those compounds which contain metals along with other impurities are called ores. These ores are used to extract metals. The complex and sequential process which is used to extract metals from their respective ores is called metallurgy. Activity 1 Surf internet to learn about metallurgical steps.

416 Oasis School Science and Technology - 10 Steps of metallurgy The metallurgical process employed for the extraction of metal depends upon its physical and chemical properties as well as the nature of impurities present in it. However, there are some common steps which are applicable for most of the metals. Some of these steps are briefly described below: 1. Mining Mining is a process in which ores of various metals are taken out from the earth crust. 2. Crushing and grinding It is a general physical step to extract metals from their respective ores. In this step, the big lumps or ores are crushed into small pieces with the help of a crusher. The pieces of ore are subjected to stamp mill to convert them into powder form. 3. Concentration In this step, unwanted earthy impurities associated with the ores, called gangue, are removed by applying different processes. Some important processes are briefly described below: a. Gravity separation / hydraulic separation This process is employed if the impurities are lighter (less denser) than ores. The lighter particles of impurities are washed away with the help of water current. Fig: gravity separation b. Forth floatation This process is employed if the impurities are hydrophilic or hydrophobic. It is applicable mostly for sulphide ores. Here, the powder are is mixed with water along with pine oil. The mixture is agitated by passing current of air. As a result, ores come to the surface and impurities remain at the bottom. Fig: froth floatation

Oasis School Science and Technology - 10 417 c. Magnetic separation This process is applicable only if the impurities or the ores are magnetic in nature. For this separation, powder ore is dropped on the moving belt of the magnetic roller. Finally, two heaps are formed, one for the magnetic substance and another for the nonmagnetic substance. d. Chemical separation (leaching) This process is applied when ores and impurities have different chemical properties. Usually powdered ores are dissolved in strong alkali solution where metal dissolves in solution and can be extracted later. 4. Oxidation of metals It this step metal oxide is obtained from its ore. The concentrated ore is heated in limited or excess air to convert it into oxide forms. There are two different steps to convert the ore into oxide forms; they are: a. Calcination This process is applicable for carbonate and hydroxide ores. These ores are heated strongly with a limited supply of air. As a result, metals are converted into metallic oxides. b. Roasting This process is applicable for sulphide ores only. These ores are heated strongly in excess supply of air. As a result of this, metals are converted into metallic oxides. c. Reduction of metal oxides In this process, free metals are obtained from the corresponding metal oxides. To convert metal oxides into free metals, different types of reducing agents like coke, hydrogen, carbon monoxide, etc. are used. If reduction process is carried out in the presence of coke, it is called smelting. Fig: Magnetic separation Fig: calcination Fig: smelting

418 Oasis School Science and Technology - 10 5. Refining It is the final step of metallurgical process through which pure metal is obtained by applying several refining processes. Distillation and electro-refining are few of them. a. Distillation It is the process to separate volatile impurities from the non-volatile metal or volatile metal from the non-volatile impurities by boiling. Volatile component will change into gas upon heating and separates from mixture. Zinc and mercury are some metals that are refined by distillation. b. Electro-refining Electro-refining is the most important process to get almost a pure form of metals. In this process impure metal is used as an anode and pure metal is used as a cathode. Salt of the same metal is used as electrolyte. After supplying electricity, salt ionizes into respective ions. Electro positive metal radical flows toward negatively charged electrode called cathode. Electronegative radical flows toward positively charged anode and takes metal from it. It ionizes again and repeats the process until all of the pure metal is eroded from anode and collected at cathode. The impurities (anode mud) are deposited at the bottom of the voltameter. Activity 2 Take an impure copper plate and connect it to the positive terminal (anode) of dry cell. Take a small piece of pure copper and connect it to the negative terminal (cathode) of dry cell. Dissolve copper sulphate in the water contained in the voltameter. Supply the electric current for some duration and observe the changes in the electrodes. Fig: distillation of ores Fig: electro refining of copper

Oasis School Science and Technology - 10 419 Some Useful Metals Iron Symbol Fe Atomic mass 56 Atomic number 26 Valency 2 and 3 Electronic Configuration 1s2 , 2s2 2p6 , 3s2 3p6 , 4s2 , 3d6 Shell K L M N No. of electrons 2 8 14 2 Position in periodic table: Period = 4, Group = VIII B (8) Block = d – Block Occurrence Iron is a reactive metal, so it does not remain freely in nature. It makes different types of compounds with other elements. A small quantity of iron is also present in blood inside the molecule of haemoglobin. Ores of Iron 1. Haematite – Fe2 O3 2. Magnetite – Fe3 O4 3. Limonite – Fe2 O3 . 3H2 O 4. Siderite – FeCO3 5. Iron pyrite – Fe2 S3 Properties of pure iron Physical properties i. Pure iron looks grey white with metallic shining. ii. It is good conductor of heat and electricity. iii. Pure iron is malleable and ductile in nature. iv. It becomes a strong magnet, as it is a magnetic substance. v. It has 7.8 specific gravity (relative density). vi. It melts at 1535°C and boils at 2450°C. Uses of iron i. It is used for making house-hold utensils, rods, wires, means of transport, buildings, bridges, weapons, tools, etc. ii. It is used as a catalyst in different types of chemical reactions. iii. Most of the construction activities depend upon iron. iv. It is used in the manufacturing of steel. Hence, it is also called the father of steel.

420 Oasis School Science and Technology - 10 v. It is the foundation of modern development and civilization. vi. It is present in the haemoglobin of the blood and helps to combine with oxygen during the process of respiration. Aluminium Symbol Al Atomic mass 27 Atomic number 13 Valency 3 Electronic configuration: 1s2 , 2s2 2p6 , 3s2 3p1 Shell K L M Electronic configuration 2 8 3 Position in the periodic table: Period-3, Group- IIIA, Block: p-Block Occurrence Aluminium is the most abundant element on the earth's crust. It is a reactive metal so it is not found freely on the nature but found in combined state. Bauxite, cryolite, feldspar, alum stone, etc. are its compounds. Ores of aluminium 1. Bauxite – Al2 O3 . 2H2 O 2. Cryolite – Na3 AlF6 3. Corundum or alumina – Al2 O3 4. Feldspar – K(AlSi3 O8 ) Properties of pure aluminium Physical properties i. It is a white coloured metal with bluish shining. ii. It is a light metal with specific gravity 2.7. iii. It is highly malleable and ductile in nature. iv. It is a good conductor of heat and electricity. v. Its melting point is 660°C and boiling point is 1800°C. Uses of aluminium i. Aluminium is used to make electric wires as it is a good conductor of heat and electricity. ii. It is used to make different types of house-hold utensils, picture frames, etc. iii. It is used for wrapping food, pharmaceutical products, biscuits, chocolate, cigarettes, etc. iv. Different parts of aircrafts, ships, cars, buses, etc. are made from aluminium. v. It is used to make alloys and coins. vi. It is used in metallurgical operations as a reducing agent.

Oasis School Science and Technology - 10 421 Copper Symbol Cu Atomic mass 63.5 Atomic number 29 Valency 1 and 2 Electronic configuration: 1s2 , 2s2 2p6 , 3s2 3p6 , 4s1 , 3d10 Shell K L M N Electronic configuration 2 8 18 1 Position in periodic table Period- 4, Group - IB, Block: d - Block Occurrence Copper is an example of coinage metal. It exists in different types of compounds like copper pyrite, copper glance, malachite, etc. These compound ores are collected from the mine and agitated with different chemical reactions to get pure copper. Ores of copper 1. Cuprite – Cu2 O 2. Copper pyrite (Chalcopyrite) – CuFeS2 3. Chalcocite (Copper glance) – Cu2 S 4. Malachite – Cu(OH)2 .CuCO3 Properties of pure copper Physical properties i. Copper is reddish brown in colour. ii. It is a good conductor of heat and electricity. iii. It is highly malleable and ductile in nature. iv. It specific gravity is 8.95, melting point is 1083°C and boiling point is 2350°C. Fact File While extracting pure copper from its ore, copper is found in molten state. It releases different gases making blisters on the surface. It is 99.4% pure. That copper is called blister copper.

422 Oasis School Science and Technology - 10 Uses of copper i. It is used for making electric cables and other electrical appliances as it is a good conductor of heat and electricity. ii. It is used to make coins, utensils, containers, etc. iii. Copper salts are used as germicides and insecticides. iv. It is used for making alloys like brass, bronze, etc. v. It is used for making different types of decorative objects. vi. Copper salt is used as an electrolyte in the process of electroplating and electro refining. Silver Symbol Ag Atomic mass 107.88 Atomic number 47 Valency 1 Electronic configuration: 1s2 , 2s2 2p6 , 3s2 3p6 , 4s2 3d10, 4p6 , 5s1 , 4d10 Shell K L M N O No. of electron 2 8 18 18 1 Position in periodic table: Period - 5, Group - IB, Block: d- Block Occurrence Silver is a white coloured shining metal which is found in a free as well as combined state in nature. In a combined state, it is present in argentite, horn silver, silver copper glance, ruby silver, etc. Ores of silver 1. Argentite/ Silver glance – Ag2 S 2. Silver copper glance – (Ag.Cu)2 S 3. Ruby Silver (pyrolite) – 3 Ag2 S . Sb2 S3 4. Horn silver – AgCl Properties of pure silver Physical properties i. It is a white coloured shining metal. ii. It is a good conductor of heat and electricity. iii. It is highly malleable and ductile in nature. iv. Its specific gravity is 10.52, melting point is 956°C and boiling point is 1955°C. Uses of silver i. Silver is used for making different types of ornaments, jewellery and coins. ii. It is used for silver plating. Fig: argentite

Oasis School Science and Technology - 10 423 iii. It is used for filling teeth. iv. Its salts are used for making silver mirrors, laboratory reagents, medicines and in photography. Gold Symbol Au Atomic mass 197 Atomic number 79 Valency 1 and 3 Electronic configuration : 1s2 , 2s2 2p6 , 3s2 3p6 , 4s2 , 3d10, 4p6 , 5s2 , 4d10, 5p6 , 6s1 , 4f14, 5d10 Shell K L M N O P No. of electron 2 8 18 32 18 1 Position in periodic table: Period - 6, Group - IB, Block: d-Block. Occurrence and ores Chemically gold is an inert metal. So, it is found in free state either mixed with quartz or alluvial soil. Very less amount of gold is also present in a combined state by making sulphide compounds. Sometimes it is also present inside the rocks. Alluvial soil or alluvial sand or quartz veins and calverite are some sources of gold. Extraction of gold Gold is mainly extracted from the alluvial soil which is rich in gold. The alluvial soil is put over the surface of zinc or iron pan and current of water is passed over it. As a result of this, unwanted earthy particles of sand and gravel are removed along with water. Other lighter particles are also washed away by leaving gold particles in the cavity of iron or zinc pan. Reasonable Fact Gold is found in a pure state in nature but not iron. Gold is a noble metal. It does not react with air, water, acids and other chemicals in normal temperature and pressure. So gold is found in a pure state. But iron combines with air, acids and other chemicals in ordinary condition to form various types of compounds. So, iron is not found in a pure state in nature. Gold is called noble metal or neutral metal. Gold does not react with air, water, acids and other chemicals in normal temperature and pressure. So, gold is called a noble metal or neutral metal. Fig: calverite rock that contains gold Fact File Gold is a less reactive metal, so it does not react with common chemical reagents like air, water, acids, etc. However, it gets dissolved in aquaregia. A mixture of 3:1 ratio of concentrated hydrochloric acid and concentrated nitric acid is known as aquaregia. It is also called kingly water because it dissolves gold to give gold chloride (AuCl3 ).

424 Oasis School Science and Technology - 10 Properties of Pure gold Physical Properties i. It is yellow coloured heavy and shining metal. ii. It is a good conductor of heat and electricity. iii. It is highly malleable and ductile in nature. iv. Its specific gravity is 19.3, melting point is 1063°C and boiling point is 2530°C v. It is the least reactive metal. Uses of gold i. Gold is used mainly for making coins, jewellery and other valuable ornaments. ii. It is used for manufacturing gold leaf electroscope. iii. It is used for gold plating over other metals. iv. Its compounds are used in photography, medicines and for filling teeth. Reasonable Fact Silver, gold, copper are called coinage metals. Silver, gold, copper are called coinage metals as they are used to make coins. Metal Valency Relative density Melting Point Ores Iron 2 and 3 7.8 1535°C Haematite (Fe2 O3 ) Magnetite (Fe3 O4 ) Limonite (Fe2 O3 .3H2 O) Siderite (FeCO3 ) Aluminium 3 2.7 660°C Bauxite (Al2 O3 . 2H2 O) Cryolite (Na3 AlF6 ) Feldspar K(AlSi3 O8 ) Copper 1 and 2 8.95 1083°C Copper pyrite or chalcopyrite (CuFeS2 ) Chalcocite or copper glance (Cu2 O) Malachite [Cu(OH)2 CuCO3 ] Silver 1 10.52 956°C Argentite (Ag2 S) Horn silver (AgCl) Gold 1 and 3 19.3 1063°C Alluvial soil or Alluvial sand or Quartz veins and Reef gold

Oasis School Science and Technology - 10 425 Reasonable Thinking Skill Reasonable Thinking Skill R T S 1. Roasted ores are heated with hydrogen or carbon monoxide. Roasted ores are heated with hydrogen or carbon dioxide to reduce metals from their oxides. 2. All minerals cannot be used to extract metals industrially. All minerals cannot be used to extract metals industrially because they contain a low concentration of metals. It would not be profitable to extract metals from them. 3. We do not need to remove gold rings while bathing, washing dishes and making pickles. We do not need to remove gold rings while bathing, washing dishes and making pickles because gold is chemically inactive. It does not react with moisture, air, water or acids. So, we can wear it without any worries. It won’t be chemically damaged. 4. Aluminium is a metal. What physical properties of aluminium make it suitable to form the body of an aeroplane? Aluminium metal is chosen to form the body of aeroplane because of the following properties: i. It forms a layer of aluminium oxide naturally and prevents rusting. ii. It is bluish-white, which is attractive. iii. It is lighter than the same volume of iron or copper. 5. Gold mines are found in Nepal at the Mahakali river, Lungri Khola, Gandaki river, Sunkoshi river and many other places. How is gold mined there? Gold is found in elemental form. It is found as a mixture in sand or alluvial soil around the Mahakali river, Lungri Khola, Sunkoshi river etc. Locals collect sand or alluvial soil in an iron pan. Then the current of water is passed through it. Since gold is heavier it is left at the bottom of the pan while mud is carried away. Thus, collected gold is melted. Electro-refining is used to make them pure. 6. Discuss the electrochemical process of refining metals. In this method, the solution of a salt of the metal to be purified is kept in a voltameter. Impure metal is used as an anode and pure metal is used as a cathode. Then the electricity is supplied. Ionization of the salt occurs. Metal radicals and non-metallic radicals will be formed. Metal radicals will start to flow from the solution and be deposited over the cathode. Negative radicals will go to the anode and erode metals. Eroded metal radicals will again travel to the cathode and deposit on it. After certain duration pure metal will be obtained from the cathode. Impurities (anode mud) will deposit under the anode. Hence metal can be purified by electrorefining. 7. Compare between calcination and roasting.

426 Oasis School Science and Technology - 10 The comparison between calcination and roasting are: SN Calcination SN Roasting 1 In calcination, the ore is heated with the least supply of air. 1 In roasting, the ore is heated with a maximum supply of air. 2 Its objective is to remove volatile impurities such as arsenic. 2 Its objective is to oxidise the impurities such as carbon and sulphur. 3 Usually, impurities are removed as carbon dioxide. 3 Usually, impurities are removed as sulphur dioxide. 8. Gold is found in elemental form. Gold is found in elemental form because its nuclear charge is too high that it cannot lose an electron. So, it cannot react with other elements to form compounds. Exercises 1. Choose the best answer from the given alternatives. a. Which metal is required for the formation of haemoglobin? i. haematite ii. iron iii. aluminium iv. copper b. Which one of the following does not rust? i. iron ii. copper iii. gold iv. aluminium c. What is metallurgy? i. study of metals ii. study of minerals iii. extraction of metals iv. utensils of metals d. Which ore is usually concentrated by the froth floatation process? i. oxide ore ii. crbonate ore iii. sulphide ore iv. alluvial soil e. Which technology is used for the refining of metals? i. amalgamation ii. electroplating iii. electrorefining iv. galvanization f. Which processes does smelting belong to? i. refining ii. grinding iii. oxidation iv. reduction 2. Define the following terms with required examples. a. Metals b. Calcination c. Minerals d. Ores e. Metallurgy f. Roasting 3. Answer the following questions in very short. a. What are the elements that lose electrons called? b. What are the sources of metals called? c. What does it mean by gravity separation? d. What does it mean by smelting?

Oasis School Science and Technology - 10 427 e. Which metal is obtained from magnetite? f. Which metal is found in elemental form? g. Which metallurgical step is the first one to purify ore? h. Which ores are roasted to oxidize? i. What is the objective of calcination? 4. Give reasons. a. All ores are minerals but all minerals cannot be ore. b. Gravity separation is used for the concentration of gold. c. Froth floatation is used for the concentration of silver sulphide. d. Haematite ore is concentrated by magnetic separation. e. Carbon monoxide is passed through the hot metal oxide. f. Iron is used for construction activities. g. Aluminium is used to make the body of vehicles. h. Copper is used to make electrical wires. i. Silver is used to make jewellery. j. Gold do not have ore. k. Gold is coated over other metals. l. Minerals cannot be used to extract metals industrially but ores can be. 5. Differentiate between the following. a. Ore and minerals b. Calcination and roasting c. Bauxite and argentite d. Oxidation and reduction 6. Answer the following questions in short. a. What are the uses of iron in our society? b. What are the uses of silver? c. How is gold used? d. Write down the uses of copper. e. Discuss the application of aluminium. f. Write a short note on the occurrence and ores of aluminium, iron, copper, silver and gold. g. What are coinage metals? In which group do they belong? h. Metallurgy is a stepwise process. Explain. 7. Answer the following questions. a. Write a short note on minerals. b. Describe general metallurgical process to extract metal. c. Write a short note on electro-refining. d. Write the ores and physical properties of iron, copper, aluminium, gold and silver. e. How is gold extracted? Describe in brief. f. How is pure copper obtained from electrorefining? Explain.

428 Oasis School Science and Technology - 10 Key terms and terminologies 1. Hydrocarbons : Compounds which are formed by the combination of carbon and hydrogen are called hydrocarbons. 2. Organic compounds : The compounds formed by reaction of carbon with elements like hydrogen, oxygen, nitrogen, etc. are called organic compounds. 3. Inorganic compounds : The compounds which are derived from minerals are called inorganic compounds. 4. Saturated hydrocarbons : The hydrocarbons in which carbon atoms are connected by a single covalent bond are called saturated hydrocarbons. 5. Unsaturated hydrocarbons: The hydrocarbons in which carbon atoms are connected by a multiple (either double or triple) covalent bond are called unsaturated hydrocarbons. 6. Alkanes : The saturated hydrocarbons in which any two carbon atoms are connected by a single covalent bond are called alkanes. UNIT 18 HYDROCARBONS AND ITS COMPOUNDS Estimated teaching periods Theory 5 Practical 1 • Introduction to hydrocarbons • Saturated and unsaturated hydrocarbon • IUPAC names and structural formula of the first four alkanes (methane, ethane, propane and n-butane) • Uses of methane, ethane, propane and n-butane • Introduction to alcohol • Functional group (hydroxide) • Types and examples of alcohol based on the number of hydroxide functional groups • Structural formula and uses of methanol, ethanol, glycol and glycerol. The Sequence of Curriculum Issued by CDC Friedrich Wohler is well known for obtaining beryllium in pure metallic form. He was born in the Roman empireon 31st July 1800 and died on 23rd September 1882. He was a German chemist and an expert on biochemistry and organic chemistry. He is also known for isomerism, Wohler synthesis and the Wohler process. He was the first to synthesise the organic compound urea. He was honoured with Copley Medal in 1872. About the Scientist Friedrich Wohler

Oasis School Science and Technology - 10 429 7. Alkenes : The unsaturated hydrocarbons in which any two carbon atoms are connected by a double covalent bond are called alkenes. 8. Alkynes : The unsaturated hydrocarbons in which any two carbon atoms are connected by a triple covalent bond are called alkynes. 9. IUPAC : The full form of IUPAC is International Union of Pure and Applied Chemistry. 10. Functional group : A functional group is an atom or group of atoms that determine the chemical properties of a hydrocarbon. 11. Homologous series : A homologous series is a group of organic compounds having similar structures. 12. Isomers : Isomers are organic compounds having the same molecular formula but different structures and properties. 13. Isomerism : Isomerism is the existence of two or more different organic compounds having the same molecular formula but different structures and properties. 14. Alcohol : Alcohol is an organic compound which contains hydroxyl group (OH). 15. Monohydric alcohol : Alcohol having only one hydroxyl group (-OH) is called monohydric alcohol. 16. Dihydric alcohol : Alcohol having two hydroxyl groups (–OH) in one compound is called dihydric alcohol. 17. Trihydric alcohol : Alcohol having three hydroxyl groups in one compound is called trihydric alcohol. 18. Glycol : Glycol is a colorless, odourless, flamable viscous dihydric alcohol having a sweet taste. 19. Glycerol : Glycerol is formed by the replacement of three hydrogen atoms from three carbons of propane by three hydroxyl groups. Glycerol is a colorless liquid having a sweet taste. Introduction Various types of chemical compounds are present in our surrounding. Most of these compounds are obtained from nature, whereas some of them are made in a laboratory or in industry. In all chemical compounds, two or more atoms of the same or different elements are present in a fixed ratio by their weight. If the compounds formed by the reaction of carbon with elements like hydrogen, oxygen, nitrogen, etc. are called organic compounds The compound which contains other elements except carbon then it is called inorganic compound. Organic and Inorganic Compounds In ancient time, scientists believed that organic compounds are produced within the body of living beings by the natural process. They also believed that formation of organic compounds takes place under the influence of vital force and they cannot be prepared in laboratory. But in 1828 AD, German chemist Friedrich Wohler synthesized urea in the laboratory by heating ammonium cyanate. Fact File There are certain compounds like CO₂ and CO that contain carbon but are traditionally called inorganic compounds. Compounds like CaCO₃, Na₂ CO₃ , etc. also contain carbon atom but they have electrovalent bond and they do not have hydrogen. So these compounds are called inorganic compounds.

430 Oasis School Science and Technology - 10 Ammonium cyanate + Heat Urea Ammonium cyanate is an inorganic compound whereas urea is an organic compound. This experiment displaced the vital force theory of organic compounds. Thereafter many organic compounds were synthesized artificially in the laboratory. The compounds formed by reaction of carbon with elements like hydrogen, oxygen, nitrogen, etc. are called organic compounds. Examples: Methane, ethane, propane, butane, alcohol, ether, glycerol, etc. The branch of chemistry in which we study about organic compounds is called organic chemistry. The compounds which are derived from minerals are called inorganic compounds. They contain other elements except hydrocarbon. For example, water, sodium chloride, calcium carbonate, hydrochloric acid, etc. The branch of chemistry in which we study about inorganic compounds is called inorganic chemistry. Hydrocarbons Those organic compounds which contain only carbon and hydrogen are called hydrocarbons. Some sources of hydrocarbons are plants, animals, fossils, petroleum etc. In hydrocarbons, the tetra co-valency of carbon is fulfilled by sharing electrons with hydrogen atoms or with other carbon atoms. Some examples of hydrocarbons with their molecular structures are given below. H C H H H Methane (CH4 ) H H C C H H H H Ethane (C2 H6 ) H H H C C H H H H C H Propane (C3 H8 ) H H C = C H H Ethene (C2 H4 ) or, Ethylene H – C ≡ C – H Ethene (C2 H4 ) or, Acetylene H C H H C Propyne (C3 H4 ) ≡ C – H Activity 1 Collect five plant materials or food and burn them one by one in a spoon. What do they leave behind? What does it suggest? Discuss. Classification of Hydrocarbons On the basis of the number of covalent bonds between carbon atoms, hydrocarbons are classified into two groups. They are: (a) Saturated hydrocarbons (b) Unsaturated hydrocarbons Fact File Most of the hydrocarbons are obtained from coal, natural gas and petroleum.

Oasis School Science and Technology - 10 431 (a) Saturated hydrocarbons Saturated hydrocarbons are the simplest organic compounds present in nature. They are also called alkanes. They contain only carbon and hydrogen atoms. Therefore, in saturated hydrocarbons there are only two types of covalent bonds; they are carbon-hydrogen bond (C – H) and carbon-carbon single bond (C – C). In these compounds, there is no double and triple covalent bond between two carbon atoms. The hydrocarbons in which carbon atoms are bonded together by a single covalent bond only are called saturated hydrocarbons. They are also called paraffins. They are comparatively stable and less reactive than unsaturated hydrocarbons. Alkanes are saturated hydrocarbons. The saturated hydrocarbons in which carbon atoms are bonded together by single covalent bonds are called alkane. Methane (CH4 ), ethane (C2 H6 ), propane (C3 H8 ), etc. are some examples of saturated hydrocarbons. The general formula to represent these saturated hydrocarbons is CnH2n+2 where n is the number of carbon atoms. To write the IUPAC name of alkanes, we add suffix "ane" at the end of total numbers of carbon atoms. The first ten members of alkane with their molecular formula, structural formula and IUPAC names are given below. S.N. No. of carbon atoms Molecular formula Structural formula IUPAC name 1. 1 (Meth) CH4 H H C H H Methane 2. 2 (Eth) C2 H6 H H C C H H H H Ethane 3. 3 (Prop) C3 H8 H H C C H H C H H H H Propane 4. 4 (But) C4 H10 H H C C H H C H H C H H H H Butane 5. 5 (Pent) C5 H12 H H C C H H C H H C H H C H H H H Pentane Fact File i. The full form of IUPAC is International Union of Pure Applied Chemistry. ii. Methane (CH₄) is single member of saturated hydrocarbons which does not contain carbon-carbon single bond. iii. Alkanes are also called paraffins as the are chemically less reactive.

432 Oasis School Science and Technology - 10 6. 6 (Hex) C6 H14 H H C C H H C H H C H H C H H C H H H H Hexane 7. 7(Hept) C7 H16 H H C C H H C H H C H H C H H C H H C H H H H Heptane 8. 8 (Oct) C8 H18 H H C C H H C H H C H H C H H C H H C H H C H H H H Octane 9. 9 (Non) C9 H20 H H C C H H C H H C H H C H H C H H C H H C H H C H H H H Nonane 10. 10 (Dec) C10H22 H H C C H H C H H C H H C H H C H H C H H C H H C H H C H H H H Decane (b) Unsaturated hydrocarbons Unsaturated hydrocarbons contain multiple covalent bonds (either double or triple) between two carbon atoms. The nature of carbon-hydrogen bond is the same for all saturated and unsaturated hydrocarbons. The hydrocarbons in which carbon atoms are bonded together by multiple (double or triple) covalent bonds are called unsaturated hydrocarbons. They are also called olefins. They are more reactive than saturated hydrocarbons. They usually take hydrogen or other foreign elements and change into saturated hydrocarbon. Ethylene (C₂H₄), acetylene (C₂H₂), propene (C₃H₆), propyne (C₃H₄), etc. are some examples of unsaturated hydrocarbons. Depending upon the number of carboncarbon covalent bonds, unsaturated hydrocarbons are of two types. They are: (i) Alkene (ii) Alkyne (i) Alkene The unsaturated hydrocarbons in which carbon atoms are bonded together by double covalent bonds are called alkene. Ethene (C2 H4 ), propene (C3 H6 ), butene (C4 H8 ), etc. are some examples of alkene. The general formula to represent alkene is CnH2n where n is the number of carbon atoms. To write the IUPAC name of alkene, we add suffix "ene" at the end of Fact File i. We cannot write methene because for the carbon-carbon double bond, at least two carbon atoms are needed. So, the first member of alkene is ethene. ii. The general formula of alkene (i.e. Cn H2n) is only applicable when there is only one double bond between carbon atoms.

Oasis School Science and Technology - 10 433 total numbers of carbon atoms. The first nine members of alkene with their molecular formula, structural formula and IUPAC names are given below. S.N. No. of carbon atoms Molecular formula Structural formula IUPAC name 1. 2 (Eth) C2 H4 H C = C H H H Ethene 2. 3 (Prop) C3 H6 = C H H H H C C H H Propene 3. 4 (But) C4 H8 H H H C C H H = C H H C H Butene 4. 5 (Pent) C5 H10 H H C H H C H H C H = C H H C H Pentene 5. 6 (Hex) C6 H12 H H C H H C H H C H H C H = C H H C H Hexene 6. 7(Hept) C7 H14 H H C H H C H H C H H C H H C H = C H H C H Heptene 7. 8 (Oct) C8 H16 H H C H H C H H C H H C H H C H H C H = C H H C H Octene 8. 9 (Non) C9 H18 H H C H H C H H C H H C H H C H H C H H C H = C H H C H Nonene 9. 10 (Dec) C10H20 H H C H H C H H C H H C H H C H H C H H C H H C H = C H H C H Decene

434 Oasis School Science and Technology - 10 ii. Alkyne The unsaturated hydrocarbons in which carbon atoms are bonded together by triple covalent bonds are called alkyne. Ethyne (C₂H₂), propyne (C₃H₄), butyne (C₄H₆), etc. are some examples of alkyne. The general formula to represent alkyne is CnH2n–2 where n is the number of carbon atoms. To write the IUPAC name of alkyne, we add suffix 'yne" at the end of total numbers of carbon atoms. The first nine members of alkyne with their molecular formula, structural formula and IUPAC names are given below. S.N. No. of carbon atoms Molecular formula Structural formula IUPAC name 1. 2 (Eth) C2 H2 H – C ≡ C – H Ethyne 2. 3 (Prop) C3 H4 H H C C H ≡ C – H Propyne 3. 4 (But) C4 H6 H C H C H H C H ≡ C – H Butyne 4. 5 (Pent) C5 H8 H H C H H C H H C H C≡ C – H Pentyne 5. 6 (Hex) C6 H10 H H C H H C H H C H H C H C≡ C – H Hexyne 6. 7(Hept) C7 H12 H H C H H C H H C H H C H H C H C≡ C – H Heptyne 7. 8 (Oct) C8 H14 H H C H H C H H C H H C H H C H H C H C≡ C – H Octyne 8. 9 (Non) C9 H16 H H C H H C H H C H H C H H C H H C H H C H C≡ C – H Nonyne 9. 10 (Dec) C10H18 H H C H H C H H C H H C H H C H H C H H C H H C H C≡ C – H Decyne

Oasis School Science and Technology - 10 435 Hydrogenation The process by which vanaspati oil is converted into vanaspati ghee by adding sufficient hydrogen atoms is called hydrogenation. C₂H₄ + H₂ C₂H₆ Fact File i. The first member of alkyne is ethyne. Methyne does not exist as there is only one carbon atom so triple covalent bond between carbons cannot be made. ii. The general formula of alkyne i.e. Cn H2n–2 is applicable only when there is a single triple covalent bond between carbon atoms. Differences between saturated and unsaturated hydrocarbons Saturated hydrocarbons Unsaturated hydrocarbons 1. In these hydrocarbons carbon atoms are bonded with single covalent bond. 1. In this hydrocarbons carbon atoms are bonded with multiple covalent bonds. 2. Saturated hydrocarbon has only one group which is alkane. 3. It is less reactive. For example; methane, ethane, propane, etc. 2. Unsaturated hydrocarbons have two groups, which are alkene and alkyne 3 It is more reactive. For example; ethene, ethyne, propene, propyne, etc. Differences between alkene and alkyne Alkene Alkyne 1. In alkene carbon atoms are bonded with double covalent bonds. 1. In alkyne carbon atoms are bounded with triple covalent bonds. 2. The general formula of alkene is CnH2n For example; ethene, propene, etc. 2. The general formula of alkyne is CnH2n–2 For example; ethyne, propyne, etc. Remember Group No. of bonds General formula Suffix Alkane C – C CnH2n+2 ane Alkene C = C CnH2n ene Alkyne C ≡ C CnH2n–2 yne Functional Group There are so many organic compounds with different number of carbon atoms. But there are some atoms or group of atoms which determine the actual chemical behaviour of these compounds. These atoms or a group of atoms are called functional groups. Atoms or a group of atoms which determine the chemical behaviour of organic compounds are called functional groups.

436 Oasis School Science and Technology - 10 Some organic compounds with their functional groups are given in the table. S.N. Name of functional group Symbol Structure Organic compounds 1. Hydroxyl –OH – OH Alcohol 2. Carboxylic acid –COOH O II – C – OH Acid 3. Ether –O– –O– Ether 4. Aldehyde –CHO O II – C – H Aldehyde 5. Keto –CO– O II – C – Ketone 6. Amino –NH2 H I – N – H Amine Alkyl Radical The group of atoms formed by removing one hydrogen from an alkane is called alkyl radical. Its general formula is CnH2n+1. For example, methyl (CH3 + ) radical is formed by removing one hydrogen atom from methane (CH4 ). Similarly, ethyl (C2 H5 + ) radical is formed by removing one hydrogen atom from ethane (C2 H6 ), etc. How are organic compounds formed? Whenever a hydrocarbon lose hydrogen, an alkyl radical is formed. When alkyl radicals combine with functional groups, it gives an organic compound. For example, Alkyl radical Functional group Organic compound – CH3 – OH CH3 – OH (Methanol) – CH3 – COOH CH3 – COOH (Acetic acid) – CH3 – CHO CH3 – CHO (Ethanal) Homologous Series Arrange some continuous members of the same organic compounds. After arranging, observe the series. What similarities and differences do we observe? Fact File Hydrogen is small in size than carbon. If atoms are small, bond will be shorter. Shorter bond will be stronger. The bond between carbon and carbon is longer than the bond between carbon and hydrogen. So, the bond between two carbon atoms is weaker than the bond between carbon and hydrogen.

Oasis School Science and Technology - 10 437 Obviously, you will see the same general formula and successive members differing by CH2 group or by molecular weight 12. Now, the series of these organic compounds is called homologous series. The series of organic compounds which has the same functional group but two successive members differ by CH2 group is called homologous series. A homologous series of alcohol is given below. CH3 – OH Methanol CH3 – CH2 – OH Ethanol CH3 – CH2 – CH2 – OH Propanol Characteristics of homologous series i. All the members of the same series have the same functional groups. For example, alcohol –OH, acid – COOH, aldehyde –CHO, etc. ii. They have the same general formula. For example; alkane CnH2n+2 iii. Two successive members of a homologous series differ by CH2 group. iv. They can be prepared with the same general methods. v. They have the same chemical properties. Nomenclature of Hydrocarbon International Union of Pure and Applied Chemistry (IUPAC) has set a fixed rule to give names to hydrocarbon. i. Detect the longest chain and count the number of carbons in it. It helps us to write word root. For example: Number of carbons word root notation C Meth C₁ C-C Eth C₂ C-C-C Prop C₃ C-C-C-C But C₄ C-C-C-C-C Pent C₅ C-C-C-C-C-C Hex C₆ C-C-C-C-C-C-C Hept C₇ C-C-C-C-C-C-C-C Oct C₈ C-C-C-C-C-C-C-C-C Non C₉ C-C-C-C-C-C-C-C-C-C Dec C₁₀ ii. Then we can add suffix based on number of covalent bonds between two carbon atoms. Such as 'ane' is added for single bond. 'ene' is added for double bond and 'yne' is added for triple bond. Illustration H H C C H ≡ C – H

438 Oasis School Science and Technology - 10 The given hydrocarbon has 3 carbon atoms. So its word root is 'prop'. It has triple covalent bond between two carbon atoms so its suffix will be 'yne'. Then its name is Prop + yne = Propyne. Some Examples of Alkane with Their Uses Methane (CH4) Methane is the first and simplest saturated hydrocarbon. At the room temperature, it occurs in a gaseous state. It is obtained by the decomposition of organic matters in swamps or marshy places, so it is also known as marsh gas. It is also present in cool mines, gobar gas and biogas. CH4 Molecule of methane H H C H H Structure of methane Uses of methane i. Methane is an important gaseous fuel as it produces a large amount of heat on burning. ii. It is used in the form of LPG for domestic use. iii. It is used for manufacturing different types of industrial chemicals like methyl chloride (CH3 Cl), chloroform (CHCl3 ), methanol (CH3 OH), carbon tetrachloride (CCl4 ), etc. iv. It is used for manufacturing carbon black, printing ink, water gas, hydrogen gas, etc. Ethane (C2H6) Ethane is the second member of saturated hydrocarbon which has molecular formula C2 H6 . It is slightly heavier than methane as it has more molecular weight than methane. Ethane also occurs with methane in natural gas, petroleum, coal etc. C2 H6 Molecular formula of ethane CH3 – CH3 Condensed structure of ethane H H C C H H H H Structural formula of ethane Uses of ethane i. Ethane is an important gaseous fuel as it produces large amount of heat on burning along with methane. ii. It is used as a laboratory reagent to produce other different types of compounds. Fact File The molecular structure of methane is tetrahedral with bond angle 109°5' in HCH.

Oasis School Science and Technology - 10 439 Propane (C3H8) Propane is the third member of saturated hydrocarbons. Its molecular formula is C₃H₈. It occurs in natural gas, LPG, petroleum mine, etc. C3 H8 Molecular formula of propane CH3 – CH2 – CH3 Condensed structure of propane H H C C H H C H H H H Structural formula of propane Uses of propane i. It is used as a fuel. ii. It is used as a refrigerant. iii. It is used to make other different types of compounds. Butane (C4H10) Butane is the fourth member of saturated hydrocarbons with molecular formula C4 H10. It occurs in petroleum mines, natural gas, etc. C4 H10 Molecular formula of butane CH3 – CH2 – CH2 – CH3 Condensed structure of butane H H C C H H C H H C H H H H Structural formula of butane Uses of butane i. It is used as a fuel. ii. It is used for manufacturing synthetic rubber, gaseous fuel and other compounds. Fact File Butane is a member of saturated hydrocarbon which has four carbon atoms. When we draw the molecular structure of butane, we get two possible structures. These two structures which have the same molecular formula but different structure formula are called isomers and the phenomenon is called isomerism. Iso-butane is called 2 methyl propane. H H C C H H C H H C H H H H (n-Butane) C C H C C H H H H H H H H H (iso-Butane)

440 Oasis School Science and Technology - 10 Alcohol In all types of alcohols, we can see the functional group -OH. It remains attached with saturated hydrocarbon or hydrocarbon radical. Some alcohols have only one hydroxyl group (–OH) whereas some have more than one. Thus, the organic compounds which contain hydroxyl group (–OH) in their molecular structure are called alcohol. Methanol (CH3 OH), ethanol (C2 H5 OH), glycol {C2 H4 (OH)2 }, glycerol {C3 H5 (OH)3 }, etc. are some examples of alcohol. Classification of alcohol On the basis of number of hydroxyl groups present, there are three types of alcohol. They are: a. Monohydric acohol b. Dihydric alcohol c. Trihydric alcohol a. Monohydric alcohol Methanol (CH3 OH), ethanol (C2 H5 OH), propanol (C3 H7 OH), etc. are some examples of monohydric alcohol. They are prepared by replacing one hydrogen atom by one hydroxyl group. Its general formula is CnH2n+1OH. Those alcohols which contain one hydroxyl group (–OH) in their molecular structures are called monohydric alcohols First five members of monohydric alcohol with their molecular formula, structural formula and IUPAC names are given in the table. S.N. Molecular Formula Structural Formula IUPAC Name 1. CH3 – OH H H C OH H Methanol 2. C2 H5 – OH H OH H C H H C H Ethanol 3. C3 H7 – OH H OH H C H H C H H C H Propanol 4. C4 H9 – OH H OH H C H H C H H C H H C H Butanol 5. C5 H11 – OH H OH H C H H C H H C H H C H H C H Pentanol

Oasis School Science and Technology - 10 441 b. Dihydric alcohol Those alcohols which contain two hydroxyl groups (–OH) in their molecular structures are called dihydric alcohols. Dihydric alcohols are obtained by replacing two hydrogen atoms of alkane by two hydroxyl groups. Its general formula is CnH2n (OH)2 . For example; glycol. H H C C H H H H (Ethane) H H C C OH H H OH (Ethylene glycol/Glycol) – 2H +2OH c. Trihydric alcohol Those alcohols which contain three hydroxyl groups (–OH) in their molecular structures are called trihydric alcohols. Its general formula is CnH2n-1 (OH)3 . H H C C C OH H H H OH OH Trihydric alcohol or Glycerol – 3H +3OH H H C C H H C H H H H Reasonable Fact The methyl alcohol is called monohydric alcohol. Methyl alchol consists of only one hydroxyl group (-OH). So, it is called monohydric alcohol. The glycerol is called trihydric alcohol. Glycerol consists of three hydroxyl (OH) groups. So, it is called a trihydric alcohol. Some Important Alcohols a. Methyl alcohol or methanol (CH3 – OH) Methanol is the first member of monohydric alcohol which has molecular formula CH3 OH. It is obtained by replacing one hydrogen of methane by one hydroxyl group (–OH). H H C OH H (Methane) (Methanol) H H C H H – H +OH Uses of methanol i. It is used as a fuel because it produces a large amount of heat without smoke. ii. It is used as an organic solvent to dissolve fats, oils, paints, etc. iii. It is used to manufacture dyes, points, perfume, medicine, synthetic fabric, etc.

442 Oasis School Science and Technology - 10 iv. It is used as a laboratory reagent to make different types of compounds like methyl chloride (CH3 Cl), formaldehyde (HCHO), etc. v. It is used for dry cleaning. b. Ethyl alcohol or ethanol (C2 H5 – OH) Ethanol is the second member of monohydric alcohol which has molecular formula C2 H5 – OH. It is obtained by replacing one hydrogen of ethane by one hydroxyl group (–OH). H H C C H H H H Ethane H H C C H H OH H Ethyl alcohol – H + OH Uses of ethanol i. It is used for drinking purposes as an alcoholic beverage. ii. It is used as a fuel in spirit lamps and stoves. iii. It is used as a thermometric liquid in an alcoholic thermometer. iv. It is used to dissolve fat, oil, paints, etc. v. It is used as a biological preservative liquid to preserve specimens. vi. It is used in medicine. c. Glycol Glycol or ethylene glycol is formed by the replacement of two hydrogen atoms from two carbons of ethane by two hydroxyl groups. Glycol is a colorless, odourless, flamable viscous liquid having a sweet taste. It is poisonous in high concentration. It's IUPAC name is ethane 1, 2 diol. H I H I I OH I OH C2 H4 (OH)2 H – C – C – H CH2 OH – CH2 OH (Molecular formula) (Condensed formula) (Structural formula) Glycol (Ethane) (Glycol) H I H I H I H I I OH I OH I H I H H–C–C–H H–C–C–H –2H +2OH Fact File Ethyl alcohol, or ethanol, is used in alcoholic drinks.

Oasis School Science and Technology - 10 443 Uses of glycol i. Glycol is used as an industrial compound to manufacture polyester fibre. ii. It is used as an anti-freeze liquid in cooling system of the engine. iii. It is used in the preparation of printing inks, ballpoint pens, stamp-pad inks, solvents, paints, plastics, films, cosmetics, etc. d. Glycerol or Trihydric alcohol Glycerol is the first member of trihydric alcohol. It has three hydroxyl groups (–OH) in its molecular structure. It is obtained by replacing three hydrogen atoms from different carbon atoms of propane with three hydroxyl groups (–OH). It is present in animal and plant fats. It is also prepared by the hydrolysis of fat or oil. It's IUPAC name is propane-1,2,3- triol. It is sweet, thick, viscous and transparent liquid. H H C C C OH H H H OH OH Propane Glycerol – 3H +3OH H H C C H H C H H H H Uses of glycerol i. It is an important preservative and sweetening agent for food. ii. It is used for manufacturing printing ink, stamp pad link, soap, cosmetics, medicines, explosives, etc. iii. It is used as a lubricant. Reasonable Thinking Skill Reasonable Thinking Skill R T S 1. Jurassica has dry lips and dry skin. Which organic compound should be used to treat dry lips and dry skin? Write the molecular formula and structural formula of the compound. Since Jurassica has dry lips and dry skin, she should use an organic compound called glycerol. Molecular formula of glycerol is C3 H5 (OH)3 . Structural formula of glycerol is 2. Carbon dioxide is not an organic compound. Carbon dioxide is not an organic compound because it does not have a covalent bond between carbon and hydrogen. Fact File i. The word glycerol has been derived from "glyceros", which means sweet. ii. Glycerol is also known as glycerine H H C C C OH H H H OH OH Glycerol

444 Oasis School Science and Technology - 10 3. Compare between glycol and glycerol. SN Paraffin SN Olefin 1 Glycol contains two hydroxyl functional group. 1 Glycerol contains three hydroxyl functional group. 2 Glycol is toxic for humans. 2 Glycerol is not toxic for humans. 4. Sugar is called an organic compound. Sugar is called an organic compound because it has a covalent bond between carbon and hydrogen atoms. 5. Write the name of the hydrocarbon shown in the picture below. What is formed when we replace one hydrogen from the first carbon atom with a hydroxyl functional group? H H C C H H C H H H H The hydrocarbon shown in the picture is a propane. If we replace one hydrogen atom with the first carbon atom, propanol will be formed. H H C C C H H H OH H H – H + OH H H C C H H C H H H H 6. It is reported that sometimes many people die by consuming locally manufactured alcohol. What actually kills them? It is reported that sometimes many people die by consuming locally manufactured alcohol. They are killed by methanol poisoning. Sometimes methanol and other volatile products are formed along with ethanol due to microbes. Methanol is poisonous. Higher concentrations of methanol can kill people. 7. What is an alkyl radical? How is it formed? What happens when a hydroxyl group is added to it? Show an example. Hydrocarbons that have lost one hydrogen is called alkyl radical. Alkyl radical is formed whenever a hydrocarbon loses hydrogen. For example: CH3 + , C2 H5 + , etc. When a hydroxyl group is added to the alkyl radical new compound is formed. For example: CH3 OH, C2 H5 OH, etc. 8. Why is ethene considered unsaturated hydrocarbon? Ethene (CH2 = CH2 ) is called unsaturated hydrocarbon because it has a double covalent bond. It can still take two more hydrogen atoms if hydrogen is available.

Oasis School Science and Technology - 10 445 9. Differentiate between paraffin and olefins. The differences between paraffin and olefins are: SN Paraffin SN Olefin 1 Paraffin is a saturated hydrocarbon. 1 Olefin is an unsaturated hydrocarbon. 2 Paraffin is less reactive. Examples: alkanes 2 Olefin is more reactive. Examples: alkenes and alkynes Exercises 1. Choose the best answer from the given alternatives. a. Hydrogen carbonate (H2 CO3 ) has carbon and hydrogen. What kind of compound is it? i. organic compound ii. hydrocarbon iii. inorganic compound iv. base b. Which one of the following is an organic compound? i. carbon dioxide ii. sugar iii. common salt iv. hydrochloric acid c. What is the structural formula of ethylene? i. ii. iii. H – C ≡ C – H iv. H H C C ≡ C – H H d. What is glycerine? i. alkane ii. alcohol iii. ether iv. ethene e. What is the molecular formula of methyl alcohol? i. CH3 OH ii. CH4 iii. CH3 CH2 OH iv. C4 H9 OH f. Which one of the following hydrocarbons belongs to the alkane series? i. ethyl glycol ii. n-butane iii. acetylene iv. methanol 2. Define the following terms with required examples. a. Organic compounds b. Saturated hydrocarbons H I H I I H I H H–C–C–H H I H I I H I H C=C

446 Oasis School Science and Technology - 10 c. Unsaturated hydrocarbons d. Alkane e. Alkene f. Alkyne g. Homologous series h. Alcohol i. Monohydric alcohol j. Dihydric alcohol k. Trihydric alcohol l. Isomerism m. Functional group n. Alkyl radical 3. Answer the following questions in very short. a. What do you mean by paraffin? Give examples. b. What are olefins? Give examples. c. Write the name of a hydrocarbon that has three carbon atoms and one double covalent bond. d. Which hydrocarbons are used in LPG? e. Which alcohol is used as a beverage? f. Write the molecular and structural formula of the following: ethylene, ethyl alcohol, glycerol, methane, ethanol, butane, propane, acetylene, ethene, ethane, propyne and methyl alcohol. g. Which organic compound is used as a skin moisturizer? h. Which alkane is used to make glycerol? i. Which alcohol is used to make the following products? i. formaldehyde ii. thermometer iii. antiseptic iv. hard drinks 4. Give reasons. a. Methane is a hydrocarbon. b. Ethane is a saturated hydrocarbon. c. Ethyne is an unsaturated hydrocarbon. d. Methane and ethane have similar chemical properties. e. Butane is used in LPG. f. Ethylene glycol should never be consumed. g. Methanol is alcohol. h. Glycerol is called trihydric alcohol. 5. Differentiate between the following. a. Saturated hydrocarbons and unsaturated hydrocarbons b. Alkane and alkene c. Alkyne and alcohol d. Monohydric alcohol and dihydric alcohol e. Methanol and glycol 6. Answer the following questions in short. a. Define hydrocarbon. Write its features.

Oasis School Science and Technology - 10 447 b. Write down the properties of alkane, alkene and alkyne. c. What are the three characteristics of homologous series? d. What happens when three hydrogen atoms of propane are replaced by three hydroxyl groups? Write its structure and two uses. e. Write the uses of ethanol. f. Write the name and uses of the hydrocarbon given below: H H C C H H C H H H H 7. Write the structure and two uses of each: a. Ethane b. Propane c. Ethylene d. Ethyne (or acetylene) e. Methanol f. Glycol 8. Answer the following questions. a. What is methane? Write its structural formula and mention its uses. b. What is the compound with the following structural formula? Mention its uses. H H C C C OH H H H OH OH c. What are the compounds shown below? Write their name and type? i. H H C C = H H C H OH ii. H H C C H H C H H OH H d. Write the name and structural formula of the compound which is formed by connecting methane by hydroxyl radical. e. Write the structural formula of acetylene. What kind of bond exists between carbon-carbon and carbon-hydrogen? Why is the bond between carbon and carbon weak? f. Observe the given compound and answer the following question. H – C ≡ C – H What is shown in the diagram? Is it saturated or unsaturated hydrocarbon? Give reason. What compound will be formed if it receives plenty of hydrogen? Write the structural formula of that compound. g. What is alcohol? Mention its types based on the number of the hydroxyl group. Write the molecular formula and structural formula of each of them.

448 Oasis School Science and Technology - 10 Key terms and terminologies 1. Food preservation : The process by which food materials are protected from spoilage is called food preservation. 2. Food preservatives : The materials or chemical substances that can be added to food to prevent spoilage are called food preservatives. 3. First class food preservatives: First class food preservatives are those which can be used in any amount without exact measuring. 4. Second class food preservatives: Second class food preservatives are those which must be used in exact amount as they are prescribed. 5. Traditional food preservatives: The spices, oils, salts, sugar, chilli, etc. that are used for ages to preserve food are called traditional food preservatives. 6. Chemical food preservatives: The group of man-made chemical substances added to food or sprayed to prevent spoilage is called chemical or synthetic food preservatives. 7. Induced ripening agents : Those chemical substances which are used to ripen fruits in short period of time are called induced ripening agents. 8. Calcium carbide : Calcium carbide is a white chemical compound with the chemical formula CaC2 . It can be used to artificially ripen fruit. UNIT 19 MATERIALS USED IN DAILY LIFE Estimated teaching periods Theory 5 Practical 1 • Introduction, importance and adverse effects of food preservatives • Introduction, importance and adverse effects of chemicals used for cleaning • Precautions while storing and using insecticides, pesticides, rodenticides, acid and chlorine • Chemical pollution from cement, glasses, ceramics, plastics, fibre, chemical fertilizer, soap and detergent. • Management of chemical pollution. The Sequence of Curriculum Issued by CDC Nicolas Appert is well known as the father of food science. He was born in France on 17th November 1749 and died on 1st June 1841. He was a French inventor of airtight food preservation. He developed a canning process (storing food in a glass jar, sealed with wax and cork then boiling) to store food such as soups, vegetables, dairy products, jellies and jamson an industrial scale. About the Scientist Nicolas Appert

Oasis School Science and Technology - 10 449 9. Antioxidants : The chemical substances that are mixed in the food to prevent oxidations are called antioxidants. 10. Pesticides : Pesticides are those chemical substances which are used to kill or chase insects, rodents, termites, fungi, etc. 11. Biodegradable pesticides: Biodegradable pesticides are those pesticides that are broken down into harmless compounds by microbes, bacteria and fungi. 12. Non-biodegradable pesticides: Non-biodegradable pesticides are those that are usually stable and do not decompose. 13. Insecticides : The toxic chemical substances that are usually used to kill or chase or disturb the reproduction of insects are called insecticides. 14. Herbicides : Herbicides are poisonous chemicals that are usually used to kill undesired plants. 15. Rodenticides : The toxic substances which are used to get rid of rodents are called rodenticides. 16. Bactericides : The poisonous chemicals used for killing or preventing the reproduction of bacteria are called bactericides. 17. Fungicides : Those chemical compounds that are used for killing fungi are called fungicides. 18. Larvicides : The poisonous chemical substances that are usually made to kill larva of insects are called larvicides. 19. Miticides : The chemicals used to get rid of mites and ticks are called miticides. 20. Contact pesticides : The chemical compounds that can kill insects, herbs, larvae, etc. that come in direct contact are called contact pesticides. 21. Systemic pesticides : Systemic pesticides are toxic chemicals that are absorbed by the body of an organism and distributed all over the body by the transportation system. 22. Stomach pesticides : The toxic chemicals that must enter the body through the mouth into the digestive system are called stomach pesticides. 23. Fumigants : The fumigants are those toxic chemicals that change into gas when exposed to moist air and kill the animals if inhaled. 24. Cleansing agents : The chemical substances which are used to remove dust, dirt, germs, foul smell, stains, etc. are called cleansing agents. 25. Synthetic cleaners : Soap, shampoo, detergents, sanitizer, stain remover, etc. are man-made synthetic cleaners. 26. Traditional cleaners : Reetha, Amla, Shikakai, wooden ash, lemon juice, clay, etc. which are used for cleaning purpose are called traditional cleansing agents. 27. Soap : Chemically soap is a sodium salt of higher fatty acid that has cleansing property in water. 28. Detergents : Detergents are sodium salts of long chain benzene sulphonic acid, which are mostly non- biodegradable with more cleansing property. 29. Chemical pollution : The pollution created by unwanted and excessive use of chemical substances is called chemical pollution.

450 Oasis School Science and Technology - 10 Introduction There are many kinds of chemical substances in our surrounding. They are both natural as well as man-made. Humans use these substances to meet their basic needs for food, shelter, clothing, and health. In ancient time, men used only natural substances to meet their needs. However, as science and human knowledge have advanced, humans are now able to create a wide range of chemical substances, such as food preservatives, antioxidants, acids, chlorine, calcium carbide, synthetic cleaners, soaps, and detergents, medicines, fertilizers, pesticides, fungicides, rodenticides, etc. We are improving the comfort, and luxury of our lives by using both natural and man-made chemical substances. The process of producing useful materials for our society by using chemical reactions is called industrial chemistry. Fig: synthetic cleansers Fig: natural food preservatives Food Preservatives The foods are natural products. They expire quickly. The majority of the food is moist. Bacteria, fungi, and moisture ruin foods like rice, grains, fruits, and meat. When food spoils, it becomes unsafe to eat. We get sick if we eat spoile food. To preserve food materials, people employ a variety of techniques. Food preservation is the process of preventing food components from spoilage. Food is traditionally preserved by dehydration, pickling, controlled fermentation, addition of salts, sugars, and spices. To preserve food in modern times, methods like canning, boiling, and adding synthetic chemical preservatives are frequently used. Food preservatives are the materials or chemicals that can be added to food to keep it from spoiling. Since ancient times, food preservatives have been utilized. Preservatives can be classified as first class and second class. First class food preservatives First class food preservatives are naturally available chemicals such as lemon, honey, sugar, vinegar etc. that can reduce microbial activities in food. It can be used in any quantity. Numbers of first class food preservatives can be used together. There are no restrictions in their uses. Second class food preservatives Second class food preservatives are usually man-made chemicals that are used to reduce microbial activities, prevent oxidation etc. Benzoic acid, sodium nitrate, sorbates, etc. are second class food preservatives. There are many Fact File There are a lot of preservatives in processed foods so we should prefer fresh food.