G9 Chemistry Past Paper PDF - 2021

U NI T  CHEMISTRY AND ITS IMPORTANCE Unit Outcomes After completing the unit, you will be able to  define chemistry;  describe its’ scope;  discuss the relationships between chemistry with physics, biology, medicine geology and ot...

U NI T  CHEMISTRY AND ITS IMPORTANCE Unit Outcomes After completing the unit, you will be able to  define chemistry;  describe its’ scope;  discuss the relationships between chemistry with physics, biology, medicine geology and other subjects;  describe the application of chemistry in the field of agriculture, medicine, food production and building construction;  name some common chemical industries in Ethiopia and their Product. 1 Chemistry Grade 9 Make groups and discuss on the following questions and present your discussion points to the class. 1. What do you think that the following materials are made of? Start-up Activity  the air you breath,  the water you drink,  the cloth you wear, and  the food you eat? 2. Why is everything in this world changing from time to time? 3. Is it important to know the materials from which everything is made up of? Why? 4. Mention some of the materials you are using commonly. Did you know who manufactured them? Since chemistry is so fundamental to our world, it plays a role in everyone’s lives and touches almost every aspect of our existence in some way. Chemistry is essential for meeting our basic needs such as food, clothing, shelter, health, energy, clean air, water, and soil. The question is how? In this unit, the definition and the scope of chemistry, the relationship between chemistry and other natural sciences, the role it plays in production and in the society, and some common chemical industries in Ethiopia and their products are presented thoroughly. 1.1 Definition and Scope of Chemistry In this section two aspects of chemistry are going to be dealt with. The first is definition of chemistry, which will be followed by the scope of chemistry. We shall begin by defining chemistry first. 1.1.1 Definition of Chemistry At the end of this section, you will be able to define chemistry. Students, form a group of three or four and discuss the question given below. Present your discussion points to the class when asked by your teacher. 1. Did you know what the composition of the salt you are adding to your meal is? 2  Chemistry and its Importance 2. What do you think will happen to the sugar crystals when you add a teaspoon of it in a cup of tea and stir it? 3. How can you distinguish table salt from sugar? 4. What happens to the wood when you burn it? Activity 1.1 Chemistry is the science that deals with the properties, composition, and structure of substances (elements and compounds), the transformations they undergo, and the energy that is released or absorbed during these processes. A substance is a particular kind of matter with uniform properties. Example, gold, silver, water, soap, table salt, etc (Figure 1.1). Matter is a physical substance, that which occupies space and possesses rest mass. Example, book, pencil, television, stool, etc. The property of a substance is its attribute, quality, or characteristic. Every substance, in the universe in which we live, has its own properties by which we can distinguish it from other substances. This is because every substance has its own unique composition and structure. Example, water is a substance that has no color, taste, and shape. Composition is the nature of something’s ingredients or constituents; how a whole or mixture is made up. Example, table salt is chemically composed of the elements sodium and chlorine. The stainless-steel spoons are solid solution (alloy) of chromium, carbon and other elements. The arrangement and relationships between the parts or elements of something complex is known as its structure. Example, the school buildings are made up of roof, ceiling, doors, windows, walls, and floor arranged in a certain order. The arrangement of each of these parts are known as the structure of the school building. Salt Sulphur Gold Silver Figure 1.1 Substances around us. Every substance in our environment is continuously changing from time to time due to both external and internal forces. Due to this change, it transforms from one form into the other. The transformation of a substance is a marked change in form, nature, or appearance. These transformations are accompanied by energy changes. 3 Chemistry Grade 9 Exercise 1.1 1. Define the term chemistry. 2. Explain the meaning of the following phrases.  property of a substance  composition of a substance  structure of a substance  transformation of a substance 1.1.2 Scope of Chemistry At the end of this section, you will be able to explain the scope of chemistry. Students, form groups of three or four. Discuss the following questions and present your discussion points to the class. 1. How do you clean: your cloth when it gets dirt, the dishes after eating meal, and your hand? 2. How does the butcher in your town measure the weight of beef before selling it? 3. Do you know how the clothes and shoes you wear, the tyres of automobiles, the different medicines you take when you are ill, and the glasses in the windows of your house are made? 4. What happens to the food in your body, after you ate it? Activity 1.2 The study of modern chemistry has many branches, but can generally be broken down into five main disciplines, or areas of study: i. Physical chemistry: It is the study of macroscopic properties, atomic properties, and phenomena in chemical systems. A physical chemist may study such things as the rates of chemical reactions, the energy transfers that occur in reactions, or the physical structure of materials at the molecular level. ii. Organic chemistry: It is the study of substances containing carbon. Carbon is one of the most abundant elements on Earth and is capable of forming a tremendously vast number of chemicals (over twenty million so far). Most of the chemicals found in all living organisms are based on carbon. 4  Chemistry and its Importance iii. Inorganic chemistry: It is the study of substances that are not primarily based on carbon. Inorganic chemicals are commonly found in rocks and minerals. One current important area of inorganic chemistry deals with the design and properties of materials involved in energy and information technology. iv. Analytical chemistry: It is the study of the composition of matter. It focuses on separating, identifying, and quantifying chemicals in samples of matter. An analytical chemist may use complex instruments to analyze an unknown material in order to determine its various components. v. Biochemistry: It is the study of chemical processes that occur in living things. It may cover anything from basic cellular processes up to understanding disease states so that better treatments can be developed. All of the aforementioned disciplines of Chemistry are highly engaged in taking measurements, making observations, and using them to come to conclusions. Chemistry is about looking for patterns in the way substances behave. Because living and non- living things are made of matter Chemistry affects all aspects of life and most natural events. The scope of Chemistry can be extended to explaining the natural world, preparing people for career opportunities, and producing informed patriot citizens. The scope of chemistry includes agriculture, medicine food production, and building construction (Figure 1.2). Figure 1.2 Some chemical products. Chemistry, however, is not only involved in providing useful substances in the areas of development and technology, but it can also result in very dangerous substances that can negatively affect human being’s life and the environment (eg. fluorochlorohydrocarbons, oxides of nitrogen, carbon, and sulphur). 5 Chemistry Grade 9 Exercise 1.2 Provide correct answer for the following questions. 1. List down examples of chemicals or chemical products that are used in the following areas:  Agriculture  Medicine  Food production  Building construction Hint: Refer Figure 1.2 above. 2. Search on the internet, and write down some of the problems caused by dangerous chemicals affecting the environment. 3. Which of the problems you find in question #2 above are observed in your locality? 4. What do you think is the solution to the problem(s)? Remember that you are an Ethiopian citizen, and have the responsibility of protecting the nation from the problems caused due to chemical substances. 1.2 The Relationship Between Chemistry and Other Natural Sciences At the end of this section, you will be able to discuss the relationship of chemistry with physics, biology, medicine, geology and other subjects. Students, form groups of three or four, and discuss the following questions. Then, present your discussion points to the class, when asked by your teacher. 1. List down the subjects that are categorized under natural science. 2. In biology class you may studied about photosynthesis. Is it possible to explain photosynthesis without having the knowledge of a chemical reaction? Reason out Activity 1.3 why? Chemistry is one branch of science. Science is the process by which we learn about the natural universe by observing, testing, and then generating models that explain our observations. Because the physical universe is so vast, there are many different branches of science ( Figure 1.3). Thus, biology is the study of living things, and geology is the study of rocks and the earth. Physics is the branch of science concerned with the nature and properties of matter and energy. 6  Chemistry and its Importance Figure 1.3 The relationships between natural sciences and chemistry. Although we divide science into different fields, there is much overlap among them. For example, some biologists and chemists work in both fields so much that their work is called Biochemistry. Biochemistry is the study of the chemical processes occurring in living matter. To give you a specific example, there are chemists who are working on the isolation, characterization and biological activities of compounds from medicinal plants. Similarly, Geology and Chemistry overlap in the field called Geochemistry. Geochemistry is defined as the study of the processes that control the abundance, composition, and distribution of chemical compounds and isotopes in geologic environments. Chemistry and Physics overlap in the areas of atomic and small molecule properties. Both of them deal with matter and energy. Physical chemistry is the branch of chemistry concerned with the application of the techniques and theories of physics to the study of chemical systems. Chemical physics is a sub discipline of chemistry and physics that investigates physicochemical phenomena using techniques from atomic and molecular physics and condensed matter physics. It is the branch of physics that studies chemical processes from the point of view of physics. Chemistry and Medicine are related in the area of Medicinal chemistry. Figure 1.3 shows how many of the individual fields of science are related. At some level, all of these fields depend on the matter as they all involve ‘stuff’. Because of this, chemistry has been called the ‘central science’ linking them all together. Exercise 1.3 Provide correct answer the following questions. 1. What aspects of nature are studied in  Physics?  Geochemistry?  Biology?  Biochemistry?  Geology?  Physical chemistry? 2. What are the regions of an overlap between  Chemistry and biology?  Chemistry and geology?  Chemistry and physics? 7 Chemistry Grade 9 1.3 The Role Chemistry Plays in Production and in the Society At the end of this section, you will be able to describe the application of chemistry in the field of agriculture, medicine, food production and building construction. Students, form groups of two or three and discuss the questions below. Present your discussion points to the class when asked by your teacher. 1. What are the common types of fertilizers the Ethiopian farmers employ to increase their crop productivity? 2. Give some examples of household materials that are used for cleaning, baking ‘diffo dabbo’, disinfecting salad, preserving raw meat, and hair treatment. 3. What types of medications (traditional and modern) are used to treat the various diseases you know? 4. What are the common types of fuels that are sold in the gas stations? Activity 1.4 There are many instances in your everyday life that involves the knowledge of chemistry, its applications, and its rules. Let us look at some of them one by one. A. Agriculture The study of chemistry has brought the world with chemical fertilizers such as calcium super phosphate, urea, ammonium sulphate, and sodium nitrate. These chemicals have assisted greatly in increasing the yield of fruits, vegetables, and other crops (Figure 1.4). Chemistry has been effective in the manufacture of pesticides, which have lessened the crop damage. Depending on the targeted pest, pesticides include fungicides, herbicides, and insecticides. Thus, we can supply to the ever-growing demand for food. Chemistry has also an important role in the manufacturing of better- quality plastic pipes for irrigation, and is commonly used in farming. This has massively increased irrigation resulting in a better climate in which the crops grow. B. Food Production Other than its great contribution in the production of different agricultural products, chemistry has led to the discovery of different kinds of food preservatives. These chemicals have greatly assisted to preserve food products for a longer period. It has given methods to test the presence of adulterants which ensure the supply of pure foodstuff. Consumers have benefited from new technologies that have increased their food’s availability, appearance, nutritional contents and flavor. A local example of food processing and keeping it for a longer period of time is the preservation of raw meat. 8  Chemistry and its Importance Figure 1.4 Agricultural products. Students, form groups of two or three and discuss the questions below. Present your discussion points to the class when asked by your teacher. 1. What are the common pests that damage crops in your locality? 2. What are the common herbs that reduce the production of food in your locality? 3. What are the commercial and traditional pesticides and herbicides used by the local farmers? Activity 1.5 C. Medicine Chemistry has provided mankind with a large number of life-saving medicines. We could find a cure for dysentery and pneumonia as a result of the discovery of Sulphur drugs and penicillin. Besides this, life-saving drugs like cisplatin and Taxol are effective for cancer therapy, and AZT is used for AIDS victims. Although AZT does not cure HIV- AIDS, it fights the multiplication of the virus thereby prolonging the life of the victim. HIV-AIDS as we know is a pandemic that has no curative medication. We need to prevent ourselves from this killer disease by being Abstain, Be faithful or reduce the number of your sex partners, and/or use a Condom. 9 Chemistry Grade 9 Common Drugs Chemistry Provided Disinfectants Analgesics Anesthetics Antibiotics Antiseptics Tranquilizers  Disinfectants: Are used to kill the microbe present in toilets, floors, and drains. The sanitizers we use for Covid-19 belong to this group.  Analgesics: An analgesic or painkiller is any member of the group of drugs used to achieve analgesia, relief from pain.  Anesthetics: Has made medical operations more and more effective via relieving pain.  Antibiotics: Are used to control infection and cure diseases.  Antiseptics: Are used to contamination of the wounds by bacteria.  Tranquillizers: To reduce tension and bring about calm and peace to patients suffering from mental diseases. Students, form groups of two or three and discuss the questions below. Present your discussion points to the class when asked by your teacher. 1. Search on the Internet or from other sources and find examples of analgesics, antibiotics, tranquilizers, antiseptics, disinfectants, anesthetics, and insecticides. 2. Describe the composition and preparation of hand disinfectant or hand sanitizer. Activity 1.6 D. Building Construction Materials By providing building resources such as glass, steel and cement, chemistry helps in the construction of safer houses and multi-story structures. It also helps in the construction of long-lasting and durable dams and bridges. The best example here could be the Grand Ethiopian Renaissance Dam (GERD) which is under construction in the Benishangul-Gumuz Region (Figure 1.5). The GERD is a 6,450 MW hydro power project nearing completion on the Blue Nile in Ethiopia, located about 30 km upstream of the border with Sudan. It will be the largest hydro power project in Africa. 10  Chemistry and its Importance Figure 1.5 The Grand Ethiopian Renaissance Dam, Benishangul Gumuz Region, Ethiopia. Figure 1.6 The role of chemistry in different sectors. Exercise 1.4 Provide correct answer for the following questions. 1. List down the role of chemistry in your locality. Draw a spider diagram of your own. 2. What problems, do you think, will be observed in the livelihood of the community in which you are living in the absence of enough knowledge of chemistry? 3. In your opinion, what further roles can chemistry play? 11 Chemistry Grade 9 1.4 Some Common Chemical Industries in Ethiopia At the end of this section, you will be able to name some common chemical industries found in Ethiopia and their products. Students, make groups of how two or three and do the following activities. Present your answers to the class when asked by your teacher. 1. List down some of the house hold chemicals? 2. Do you know which industry is producing them? 3. List down the common chemical industries (enterprises) found in your locality or in the vicinity of your town. Which chemicals or chemical products are they producing? Activity 1.7 An industry is defined as an economic activity concerned with the processing of raw materials and the manufacture of goods in factories. It can also be interpreted as a group of companies that are linked based on their primary business activities. Individual companies are generally categorized into an industry based on their largest sources of revenue. The Ethiopian government is highly engaged in expanding industries in the past two decades. As part of this expansion several industrial parks have been under construction (Figure 1.7). Figure 1.7 One of the industrial parks found in Ethiopia. The chemical industries comprise the companies that manufacture inorganic- and organic-industrial chemicals, explosives, fragrances, agrochemicals, polymers and 12  Chemistry and its Importance rubber, ceramic products, petrochemicals, oleochemicals (oils, fats, and waxes), and flavors. Central to the world economy, it converts natural resources (oil, natural gas, air, water, metals, and minerals) into diverse products. They are further categorized into industrial inorganic chemicals; plastics, materials, and synthetics; drugs; soap, cleaners, and toilet goods; paints and allied products; industrial organic chemicals; agricultural chemicals; and miscellaneous chemical products. The chemical products mean products manufactured, processed, sold, or distributed by the company that are chemical substances, or that contained chemical substances. Three general classes of products are (1) basic chemicals such as alkalis, acids, organic chemicals, and salts (2) chemical products to be used in further manufactures such as plastic materials, synthetic fibers, pigments, and dry colors, and (3) finished chemical products to be used for ultimate consumption such as cosmetics, drugs, and soaps; or to be used as materials or supplies in other industries such as fertilizers, paints, and explosives. Currently, there are several medium and large-scale chemical and chemical products industries (enterprises) in Ethiopia (Table 1.1). These enterprises produce chemicals like aluminum sulphate, caustic soda, soda ash, carbon dioxide, bleaching chemicals, magnesium oxide, pesticides, and chemical products like soap and detergent, cement, paints, building materials, cosmetics, plastic, natural gum, candle, glass, sugar, tyre, pulp and paper, pharmaceuticals and tobacco. Table 1.1 Some of the large and medium scale chemical enterprises in Ethiopia. No. Name of the Enterprise City Product 1 Chorra Gas & Chemical A.A Plastic, chemicals, petroleum products products 2 Chorra Gas & Chemical A.A Aluminum sulphate and sulphuric acid products 3 Ziway Caustic Soda Ziway Sodium hydroxide factory 4 Abijata Soda Ash Bulbula Trona (Na3H(CO3)2.2H2O) Factory 5 Repi Soap & Detergent A.A Soap and detergent P.L.C 6 Adola Magnesium Adolla Magnesium oxide Oxide Factory 7 Adami Tulu Pesticide Adami-Tulu Formulates malathion, endosulfan, Processing Plant diazinon, fenitrothion and dimethoate 8 Nefas Silk Paints A.A Paints, varnishes, antirusts and glues factory 13 Chemistry Grade 9 No. Name of the Enterprise City Product 9 Modern Building A.A Cement and cement products, Industries ceramics, paints, sanitary ware, adhesives, glues, plastic rubber, terrazzo tiles, cultured marble 10 Kadisco Chemical A.A Paints, coatings and adhesives Industry 11 Tadesse Filatea PLC Woliso Soap, detergent, corrugated iron, nail, infant milk formula 12 Etab Laundry Soap Hawassa Soap and detergent Factory 13 Get-Eshet Detergent Bishoftu Detergent products and Leather Manufacturing and chemical inputs Packing P.L.C 14 Ethio-Asia Industries S.C A.A Soap and detergent 15 Y.B Cosmetics Sheger city Cosmetics and perfume 16 Mekab PLC (Cosmetics) A.A Hair oil, shampoo, conditioner, body oil, vaseline, body lotion, detergents and plastic mouldings 17 BEKAS Chemicals PLC A.A Detergents, cosmetic products, plastic packing materials, industrial surfactants and putty 18 Arbaminch Textile Arbaminch Textile and fabric products Share compary 19 Teamco Soap Factory Burayu Soap and detergent Note: A.A stands for Addis Ababa. Other chemical product industries in Ethiopia.  Cement (Mugher, Diredawa, Mesobo, Derba, Midroc, Dangote)  Sugar (Metehara, Wonji, Finchaa, Omokuraz)  Paper and pulp (Wonji)  Pharmaceuticals (Addis, Ethiopia, Adigrat)  Tyre (Horizon Addis Tyre) 14