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Classify the changes involved in the following, processes as physical or chemical changes:, , (a) Photosynthesis, Chemical change, (b) Dissolvingsugar in water :, Physical change, Chemical change, (c) Burning of coal, (d) Melting of wax, Physical change, (e) Beating aluminiumto make aluminiumfoil:, Physical change, Chemical change, (f) Digestion of food
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State, , whether, , the, , following, , statements, , are, , true, , or false. In case a statementis false, write the, , corrected statement in your notebook., , (a) Cutting a log of wood into pieces is a chemical, change., (False), Corrected Statement:, Cutting a log of wood into pieces is a physical, change.
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State, , whether, , the, , following, , statements, , are, , true, , or false. In case a statementis false, write the, corrected statement in your notebook., , (b) Formationof manurefrom leaves is a physical, change., , Corrected Statement:, Formation of manure from leaves is, , (False), , a chemical, , change., , (c) Iron pipes coated with zinc do not get rusted, easily., (True)
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State, , whether, , the, , following, , statements, , are, , true, , or false. In case a statementis false, write the, corrected statement in your notebook., , (d) Iron and rust are the samesubstances., (False), , Corrected Statement:, Iron and rust are different substances., (e) Condensationof steam is not a chemical, change., (True)
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(a) When carbon dioxide is passed through lime, water. it turns milky due to the formation of, calcium carbonate, (b) The chemical name of baking soda is, sodium hydrogen carbonate, , (c) Two methods by which rusting of iron can be, prevented are, , painting, , and, , greasing
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Fill in the blanks in the followingstatements:, , (d) Changes in which only, , physical, , properties, , of a substance change are called physical, changes., , (e) Changes in which new substances are formed, are called chemical changes.
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When, , baking, , soda, , is, , mixed, , with, , lemon, , juice,, , bubblesare formed with the evolutionof a gas., What type of change is it? Explain., , Ans., , This is a chemicalchangeas new products, are formed., , Baking soda + Lemonjuice -+Carbon dioxide + other substances
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When, , a candle, , burns., , both, , physical, , and, , chemical, , changes take place. Identify these changes. Give, , another exampleof a familiar process in which, , both the chemical and physical changes take, place., , Ans., , Physical change:, Chemical change:, , Melting of wax., Burning of wax to form, carbon, , dioxide, , other products., Another example:, , Cooking of food., , and
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How would you show that setting of curd is a, chemical change?, , Ans., , This is a chemicalchangebecausea, , new, , substance is formed. Also, this change, cannot be reversed.
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why, , burning, , of, , wood, , and cutting, , it, , into, , small pieces are considered as two different, types of changes., , Ans., , Burning of wood is a chemical change, because new substances are formed like, ash. carbon dioxide. water vapouretc., Cutting wood into small pieces is a physical, change because no new substances are, formed., UVLearn
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Describe how crystals of copper sulphate are, prepared., , Ans., , Take somewater in a beaker., Add a few drops of dilute sulphuricacid., Boil the water and add copper sulphate, powder while stirring till it becomes, saturated., , Filter it and let it to cool down.The, crystals of copper sulphate separate out., This process is called crystallisation.
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Explain how painting of iron gate prevents it from, rusting., , Ans., , Rusting of iron requires water (moisture) and, oxygen. Painting of iron gate prevents it to, get in contact with water and oxygen and, thus prevents it from rusting.
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Explain why rusting of iron objects is faster in, coastal areas than in deserts., , Ans., , Rusting of iron requires water (moisture) and, oxygen. In coastal areas. the quantity of, , moisture in air is higher than in deserts., So, the rusting of iron is faster in coastal, areas.
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The, , gas, , we, , use, , in the, , kitchen, , is called, , liquified, , petroleumgas (LPG). In the cylinderit exists as, , 11, , liquid. When it comes out from the cylinder, it, becomesa gas (Change- A) then it burns (Change, B). The following statements pertain to these, changes. Choosethe correct one., , (i) Process- A is a chemicalchange., Process- B is a chemicalchange., (iii) Both processes A and B are chemical changes., (iv) None of these processes is a chemicalchange., , Ans., , (ii) Process- B is a chemicalchange.
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Anaerobic bacteria digest animal waste and, produce biogas (Change - A). The biogas is then, , 12, , burnt as fuel (Change, , B). The following, , statements pertain to these changes. Choose the, correct one., , (i) Process- A is a chemicalchange., (ii) Process- B is a chemicalchange., Both processes A and B are chemical changes., (iv) None of these processes is a chemicalchange., Ans., , (iii) Both processesA and B are chemicalchanges.
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Name the gas which turns lime water milky., oCarbon dioxide gas (C02) turns lime water milky.
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What colour of flame is observed when, magnesiumribbon is burnt in air., , When magnesium is burnt in air then a, brilliant white flame is obtained.
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How can you say that ripening of a fruit is a, chemical change?, Ripening of a fruit is a chemical change because after, ripening, a new product with different properties is, formed. This process can not be reversed also.
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What is the nature of magnesium oxide, solution?, Magnesium oxide is basic in nature because it turns, red litmus solution to blue.
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We should eat freshly cut apple. Why?, oWe should eat freshly cut apple because if we leave, the apple after cutting, it starts turning brownish due, to the oxidation of the essential nutrients present in it, and its food value decreases.
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Why do people paint the iron gates of their, houses during the rainy season?, oDuring rainy season, the iron gates are directly, exposed to the rain water and air, which causes, rusting. Rusting is a continuous process that corrodes, the metal and makes it less durable, and it occurs in, the presence of air and water. Hence, the iron gates are, coated with paint to prevent corrosion.
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Physical change, 1. Precipitation is an, example of this., 2. Composition of, substance remains same., , 3. It is usually temporary., , 4. It is reversible., , Chemical change, 5. New substances are, formed., , 6. Products have new, composition., , 7. It is usually permanent., 8. Burning of LPG is an, example of this.
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Suggest methods to prevent rusting., Rusting of iron can be prevented by following methods:, (a) Painting: A coat of paint applied on the surface of an iron, object prevents oxygen and moisture present in the atmosphere, from interacting with the iron object., (b) Oil or grease: Applying oil or grease on the surface of iron, tools helps to keep out the oxygen and moisture of the, atmosphere., (c) Galvanization: Galvanization is a process of coating iron, objects with a thin layer of metal such as zinc. A thin coating of, zinc protects the iron from rusting.
