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train/chapter 1 1-46 (1).mp3 | Chemical Reactions and Equations | 5.003 |
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train/chapter 1 1-46 (10).mp3 | We have already learnt about physical and chemical changes of matter in our previous classes. | 5.003 |
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train/chapter 1 1-46 (11).mp3 | Whenever a chemical change occurs, we can say that a chemical reaction has taken place. | 5.003 |
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train/chapter 1 1-46 (12).mp3 | You may perhaps be wondering as to what is actually meant by a chemical reaction. | 5.003 |
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train/chapter 1 1-46 (13).mp3 | How do we come to know that a chemical reaction has taken place? | 5.003 |
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train/chapter 1 1-46 (14).mp3 | Let us perform some activities to find the answer to these questions. | 5.003 |
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train/chapter 1 1-46 (15).mp3 | CAUTION: | 5.003 |
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train/chapter 1 1-46 (16).mp3 | This Activity needs the teacher’s assistance. | 5.003 |
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train/chapter 1 1-46 (17).mp3 | It would be better if students wear eye protection. | 5.003 |
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train/chapter 1 1-46 (18).mp3 | Clean a magnesium ribbon about 2 cm long by rubbing it with sandpaper. | 5.003 |
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train/chapter 1 1-46 (19).mp3 | Hold it with a pair of tongs. | 5.003 |
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train/chapter 1 1-46 (2).mp3 | Consider the following situations of daily life and think what happens when – | 5.003 |
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train/chapter 1 1-46 (20).mp3 | Burn it using a spirit lamp or burner and collect the ash so formed in a watch-glass. | 5.003 |
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train/chapter 1 1-46 (21).mp3 | Burn the magnesium ribbon keeping it as far as possible from your eyes. | 5.003 |
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train/chapter 1 1-46 (22).mp3 | What do you observe? | 5.003 |
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train/chapter 1 1-46 (23).mp3 | Burning of a magnesium ribbon in air and collection of magnesium oxide in a watch-glass | 5.003 |
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train/chapter 1 1-46 (24).mp3 | You must have observed that magnesium ribbon burns with a dazzling white flame and changes into a white powder. | 5.003 |
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train/chapter 1 1-46 (25).mp3 | This powder is magnesium oxide. | 5.003 |
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train/chapter 1 1-46 (26).mp3 | It is formed due to the reaction between magnesium and oxygen present in the air. | 5.003 |
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train/chapter 1 1-46 (27).mp3 | Take lead nitrate solution in a test tube. | 5.003 |
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train/chapter 1 1-46 (28).mp3 | Add potassium iodide solution to this. | 5.003 |
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train/chapter 1 1-46 (29).mp3 | What do you observe? | 5.003 |
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train/chapter 1 1-46 (3).mp3 | milk is left at room temperature during summers. | 5.003 |
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train/chapter 1 1-46 (30).mp3 | Take a few zinc granules in a conical flask or a test tube. | 5.003 |
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train/chapter 1 1-46 (31).mp3 | Add dilute hydrochloric acid or sulphuric acid to this. | 5.003 |
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train/chapter 1 1-46 (32).mp3 | Do you observe anything happening around the zinc granules? | 5.003 |
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train/chapter 1 1-46 (33).mp3 | Touch the conical flask or test tube. Is there any change in its temperature? | 5.003 |
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train/chapter 1 1-46 (34).mp3 | From the above three activities, we can say that any of the following observations helps us to determine whether a chemical reaction has taken place – | 5.003 |
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train/chapter 1 1-46 (35).mp3 | change in state | 5.003 |
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train/chapter 1 1-46 (36).mp3 | change in colour | 5.003 |
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train/chapter 1 1-46 (37).mp3 | evolution of a gas | 5.003 |
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train/chapter 1 1-46 (38).mp3 | change in temperature. | 5.003 |
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train/chapter 1 1-46 (39).mp3 | As we observe the changes around us, we can see that there is a large variety of chemical reactions taking place around us. | 5.003 |
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train/chapter 1 1-46 (4).mp3 | an iron tawa/pan/nail is left exposed to humid atmosphere. | 5.003 |
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train/chapter 1 1-46 (40).mp3 | We will study about the various types of chemical reactions and their symbolic representation in this Chapter. | 5.003 |
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train/chapter 1 1-46 (41).mp3 | Formation of hydrogen | 5.003 |
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train/chapter 1 1-46 (42).mp3 | when a magnesium ribbon is burnt in gas by the action of dilute sulphuric acid on oxygen, it gets converted to magnesium oxide. | 5.003 |
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train/chapter 1 1-46 (5).mp3 | grapes get fermented. | 5.003 |
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train/chapter 1 1-46 (6).mp3 | food is cooked. | 5.003 |
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train/chapter 1 1-46 (7).mp3 | food gets digested in our body. | 5.003 |
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train/chapter 1 1-46 (8).mp3 | we respire. | 5.003 |
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train/chapter 1 1-46 (9).mp3 | In all the above situations, the nature and the identity of the initial substance have somewhat changed. | 5.003 |
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train/chapter 1 112-151 (1).mp3 | Do you feel any change in temperature? | 5.003 |
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train/chapter 1 112-151 (10).mp3 | Let us discuss some more examples of combination reactions. | 5.003 |
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train/chapter 1 112-151 (11).mp3 | In simple language we can say that when two or more substances (elements or compounds) combine to form a single product, the reactions are called combination reactions. | 5.003 |
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train/chapter 1 112-151 (12).mp3 | we also observed that a large amount of heat is evolved. | 5.003 |
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train/chapter 1 112-151 (13).mp3 | This makes the reaction mixture warm. | 5.003 |
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train/chapter 1 112-151 (14).mp3 | Reactions in which heat is released along with the formation of products are called exothermic | 5.003 |
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train/chapter 1 112-151 (15).mp3 | chemical reactions. | 5.003 |
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train/chapter 1 112-151 (16).mp3 | We all know that we need energy to stay alive. | 5.003 |
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train/chapter 1 112-151 (17).mp3 | We get this energy from the food we eat. | 5.003 |
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train/chapter 1 112-151 (18).mp3 | During digestion, food is broken down into simpler substances. | 5.003 |
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train/chapter 1 112-151 (19).mp3 | For example, rice, potatoes and bread contain carbohydrates. | 5.003 |
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train/chapter 1 112-151 (2).mp3 | Formation of slaked lime by the reaction of calcium oxide with Calcium oxide reacts vigorously with water to produce slaked lime water (calcium hydroxide) releasing a large amount of heat. | 5.003 |
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train/chapter 1 112-151 (20).mp3 | These carbohydrates are broken down to form glucose. | 5.003 |
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train/chapter 1 112-151 (21).mp3 | This glucose combines with oxygen in the cells of our body and provides energy. | 5.003 |
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train/chapter 1 112-151 (22).mp3 | The decomposition of vegetable matter into compost is also an example of an exothermic reaction. | 5.003 |
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train/chapter 1 112-151 (23).mp3 | Decomposition Reaction | 5.003 |
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train/chapter 1 112-151 (24).mp3 | Take about 2 g ferrous sulphate crystals in a dry boiling tube. | 5.003 |
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train/chapter 1 112-151 (25).mp3 | Note the colour of the ferrous sulphate crystals. | 5.003 |
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train/chapter 1 112-151 (26).mp3 | Heat the boiling tube over the flame of a burner or spirit lamp. | 5.003 |
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train/chapter 1 112-151 (27).mp3 | Observe the colour of the crystals after heating. | 5.003 |
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train/chapter 1 112-151 (28).mp3 | Have you noticed that the green colour of the ferrous sulphate crystals? | 5.003 |
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train/chapter 1 112-151 (29).mp3 | Correct way of heating the boiling tube has changed. | 5.003 |
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train/chapter 1 112-151 (3).mp3 | In this reaction, calcium oxide and water combine to form a single product, calcium hydroxide. | 5.003 |
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train/chapter 1 112-151 (30).mp3 | You can also smell the characteristic odour of burning containing crystals sulphur of ferrous sulphate. | 5.003 |
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train/chapter 1 112-151 (31).mp3 | Ferrous sulphate crystals lose water when heated and the colour of the crystals changes. | 5.003 |
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train/chapter 1 112-151 (32).mp3 | It then decomposes to ferric oxide, sulphur dioxide and sulphur trioxide. | 5.003 |
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train/chapter 1 112-151 (33).mp3 | Ferric oxide is a solid, while SO2 and SO3 are gases. | 5.003 |
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train/chapter 1 112-151 (34).mp3 | Decomposition of calcium carbonate to calcium oxide and carbon dioxide on heating is an important decomposition reaction used in various industries. | 5.003 |
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train/chapter 1 112-151 (4).mp3 | Such a reaction in which a single product is formed from two or more reactants is known as a combination reaction. | 5.003 |
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train/chapter 1 112-151 (5).mp3 | Do You Know? | 5.003 |
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train/chapter 1 112-151 (6).mp3 | A solution of slaked lime produced by the reaction is used for white washing walls. | 5.003 |
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train/chapter 1 112-151 (7).mp3 | Calcium hydroxide reacts slowly with the carbon dioxide in air to form a thin layer of calcium carbonate on the walls. | 5.003 |
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train/chapter 1 112-151 (8).mp3 | Calcium carbonate is formed after two to three days of white washing and gives a shiny finish to the walls. | 5.003 |
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train/chapter 1 112-151 (9).mp3 | It is interesting to note that the chemical formula for marble is also CaCO3. | 5.003 |
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train/chapter 1 146-151 (1).mp3 | Calcium oxide is called lime or quick lime. | 5.003 |
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train/chapter 1 146-151 (2).mp3 | It has many uses – one is in the manufacture of cement. | 5.003 |
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train/chapter 1 146-151 (3).mp3 | When a decomposition reaction is carried out by heating, it is called thermal decomposition. | 5.003 |
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train/chapter 1 146-151 (4).mp3 | Take about 2 g lead nitrate powder in a boiling tube. | 5.003 |
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train/chapter 1 146-151 (5).mp3 | Hold the boiling tube with a pair of tongs and heat it over a flame. | 5.003 |
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train/chapter 1 146-151 (6).mp3 | What do you observe? | 5.003 |
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train/chapter 1 152-197 (1).mp3 | Note down the change, if any. | 5.003 |
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train/chapter 1 152-197 (10).mp3 | Fill the mug with water such that the electrodes are immersed. | 5.003 |
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train/chapter 1 152-197 (11).mp3 | Add a few drops of dilute sulphuric acid to the water. | 5.003 |
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train/chapter 1 152-197 (12).mp3 | Take two test tubes filled with water and invert them over the two carbon electrodes. | 5.003 |
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train/chapter 1 152-197 (13).mp3 | Switch on the current and leave the apparatus undisturbed for some time. | 5.003 |
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train/chapter 1 152-197 (14).mp3 | You will observe the formation of bubbles at both the electrodes. | 5.003 |
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train/chapter 1 152-197 (15).mp3 | These bubbles displace water in the Electrolysis of water test tubes. | 5.003 |
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train/chapter 1 152-197 (16).mp3 | Is the volume of the gas collected the same in both the test tubes? | 5.003 |
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train/chapter 1 152-197 (17).mp3 | Once the test tubes are filled with the respective gases, remove them carefully. | 5.003 |
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train/chapter 1 152-197 (18).mp3 | Test these gases one by one by bringing a burning candle close to the mouth of the test tubes. | 5.003 |
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train/chapter 1 152-197 (19).mp3 | CAUTION: | 5.003 |
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train/chapter 1 152-197 (2).mp3 | You will observe the emission of brown fumes. | 5.003 |
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train/chapter 1 152-197 (20).mp3 | This step must be performed carefully by the teacher. | 5.003 |
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train/chapter 1 152-197 (21).mp3 | What happens in each case? | 5.003 |
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train/chapter 1 152-197 (22).mp3 | Which gas is present in each test tube? | 5.003 |
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train/chapter 1 152-197 (23).mp3 | Take about 2 g silver chloride in a china dish. | 5.003 |
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train/chapter 1 152-197 (24).mp3 | What is its colour? | 5.003 |
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train/chapter 1 152-197 (25).mp3 | Place this china dish in sunlight for some time. | 5.003 |
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