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Class 9 Science Chapter 14 Substances in, , Common Use Textbook Questions and Answers, , 1. Fill in the blanks., , a. The number of molecules of water of, crystallization in washing Soda is ............-++ +, , b. The chemical name of baking soda is, , C. ceessessseeeene IS USEd in treatment of, hyperthyroidism., , d. The chemical name of Teflon is ...............0. Answer:, , a. 10, , b. Sodium bicarbonate, , c. lodine -123, , d. Polytetra fluoroethylene (C2F4)n,
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Group A, , 1. Saturated brine, 2. Fused salt, , 3. CaOCly, , 4. NaHCO3, , Group B, , a. sodium metal freed, , b. basic salt, , c. crystallization of salt, , d. oxidation of colour
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3. Write answers to the following, , a. What is meant by radioactivity?, , Answer:, , ¢ Elements with a high atomic number such, as uranium, thorium, radium have a, property of spontaneously emitting, invisible, highly penetrating and high, energy radiation., , ¢ This property is called radioactivity., , ¢ A substance having this property is called, , a radioactive substance.
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b. When is said to be the nucleus unstable?, , Answer:, , ¢ It is the balance of protons and neutrons, in a nucleus which determines whether a, nucleus will be stable or unstable., , * Too many neutrons or protons upset this, balance disrupting the binding energy, from the strong nuclear forces making, , the nucleus unstable., , c. Which diseases are caused by artificial food, colours?, , Answer:, , Diseases like ADHD (Attention Deficit, Hyperactivity Disorder) can affect children due, to excessive consumption of foods with added, , food colours.
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d. Where in the industrial field is radioactivity, used?, Answer:, , Industrial field Radiography, , * Internal cracks and voids in cast iron, articles and iron solder can be detected, with the help of gamma rays., , * For this purpose, isotopes like cobalt-60,, iridium-192 are used in the radiography, camera., , * This technique is used for detecting flaws, , in metal work., , Measurement of thickness, density and level, , * It is necessary to maintain the required, thickness in the manufacture of, aluminium, plastic, iron sheets of differing, , thickness., , In the manufacturing process, a, radioactive substance is placed on one, side and an instrument to measure, , radiation on the other., , The radiation read by the measuring, instrument varies with the thickness of, , the sheet., , Material inside a packing can also be, , examined by the same technique., Luminescent paint and radio luminescence:, , * The radioactive substances radium,, promethium, tritium with some phosphor, are used to make certain objects visible in, the dark, for example, the hands of a, clock, and certain other objects., , * Krypton-85 is used in HID (High-Intensity, Discharge) lamps while promethium —, , 147 is used in portable X-ray units as the, , source of beta rays., , Use in Ceramic articles:, , * Luminous colours are used to decorate, ceramic tiles, utensils, plates, etc., + Earlier uranium oxide was used in these, , paints.
