\n
![\"KSEEB](\"https:\/\/live.staticflickr.com\/65535\/48130566083_6228b36403_o.png\")
\nAnswer:<\/p>\n
I. Four alternatives are given to each of the following incomplete statement\/questions. Choose the right answer.<\/p>\n
Question 1.
\nMagnesium sulfate crystals are commonly called …………..
\na) Gypsum salt
\nb) Epsom slat
\nc) green vitriol
\nd) Alum
\nAnswer:
\nb) Epsom slat<\/p>\n
Question 2.
\nWhen you buy washing soda from the market, you will get it in powder form because ………….
\na) The crystals of washing soda quickly lose water molecule
\nb) The shop keeper prefers to power the crystal.
\nc) washing soda does not form crystals
\nd) washing soda is a drying agent
\nAnswer:
\na) The crystals of washing soda quickly lose water molecule<\/p>\n
Question 3.
\nA sample of hard water is heated in a utensil a white deposit of calcium carbonate is formed. This is due to the presence of ….
\na) calcium chloride
\nb) magnesium sulfate
\nc) calcium bicarbonate
\nd) calcium hydroxide
\nAnswer:
\nc) calcium bicarbonate<\/p>\n
Question 4.
\nThe salt that cause hardness in water and that liberates carbon dioxide on heating is
\na) magnesium bicarbonate
\nb) calcium chloride
\nc) magnesium sulfate
\nd) calcium sulfate
\nAnswer:
\na) magnesium bicarbonate<\/p>\n
Question 5.
\nWhen steam is passed over red hot …………. iron we get the following products
\na) Ferric hydroxide and hydrogen
\nb) Ferric oxide and hydrogen
\nc) Ferrous hydroxide and hydrogen
\nd) Ferrous ferric oxide and hydrogen
\nAnswer:
\nd) Ferrous ferric oxide and hydrogen<\/p>\n
II. Fill in blanks with suitable words :<\/p>\n
Question 1.
\nThe chemical name of Epsom salt is ………..
\nAnswer:
\nsulfate (Magnesium)<\/p>\n
Question 2.
\nThe chemical used to soften hard water is …………..
\nAnswer:
\nsodium carbonate<\/p>\n
III. Match the following :
\n
\nAnswer:<\/p>\n
IV. Answer the following:<\/p>\n
Question 1.
\nWater is tasteless, but we experience different tastes of water in different places. Why?
\nAnswer:
\nWater obtained from different places has several salts dissolved in it, therefore, water has different taste even though pure water is tasteless.<\/p>\n
Question 2.
\nWrite the balanced equations for the reaction of sodium, potassium and calcium on cold water.
\nAnswer:<\/p>\n
Question 3. Question 4. Question 5. Question 6. Question 7. Answer:<\/p>\n Question 8. V. Give reasons for the following :<\/p>\n Question 1. Question 2. Question 3. Question 1. Question 2. Question 3. Question 4. Question 6. Question 7. Question 8. Question 9. Question 10. Question 11. Question 12. Question 13. Question 14. Question 15. Question 16. Question 17. Question 18. Question 19. Question 20. Question 21. Question 22. Question 23. Question 24. Question 25. Take some hard water in a beaker, and add a small quantity of washing soda to it stir it with a glass rod. Allow the insoluble carbonates to settle down or precipitate. Filter or decant the liquid. Water so obtained is soft water. But it is unfit for drinking as it contains an excess of washing soda and excess of sodium salts.<\/p>\n Question 26. Karnataka Board Class 8 Science Chapter 13 Water KSEEB Class 8 Science Chapter 13 Textual Questions & Answers I. Four alternatives are given to each of the following incomplete statement\/questions. Choose the right answer. Question 1. Magnesium sulfate crystals are commonly called ………….. a) Gypsum salt b) Epsom slat c) green vitriol d) Alum Answer: …<\/p>\n","protected":false},"author":5,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/posts\/4967"}],"collection":[{"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/comments?post=4967"}],"version-history":[{"count":0,"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/posts\/4967\/revisions"}],"wp:attachment":[{"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/media?parent=4967"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/categories?post=4967"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/tags?post=4967"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\nWhat happens When steam is passed over red hot iron? Write the equation.
\nAnswer:
\nWhen steam is passed over red hot iron hydrogen is liberated along with the formation of ferric oxide.
\n3Fe + 4H2<\/sub>O \u2192 Fe \u2191 + 4H2<\/sub><\/p>\n
\nDefine the terms efflorescence and Deliquescent.
\nAnswer:<\/p>\n\n
\nGive two reasons to prove that water is a compound and not an element.
\nAnswer:
\nThough water contains combustible hydrogen and supporter of combustion oxygen, water is neither a supporter of combustion nor a combustible substance. Water has a different property which hydrogen and oxygen do not have i.e., it is a very good fire extinguisher, compound does not show the properties of elements by which it is formed but it will have a different property since it is a new substance. By this one can prove that water is a compound.<\/p>\n
\nName three metals which do not react with water under normal conditions.
\nAnswer:
\nCopper, tin and aluminium are the three metals which do not react with water under normal conditions.<\/p>\n
\nName the products formed when the following oxides are dissolved in water. Write balance of equation.<\/p>\n\n
\n
\nSO2<\/sub> + H2<\/sub>O \u2192 H2<\/sub>SO3<\/sub><\/li>\n
\nKO + H2<\/sub>O \u2192 KOH<\/li>\n
\nCaO +H2<\/sub>O \u2192 Ca(OH)2<\/sub><\/li>\n
\nCO2<\/sub>+ H2<\/sub>O \u2192 H2<\/sub>CO3<\/sub><\/li>\n<\/ol>\n
\nState the reasons for hardness in water.
\nAnswer:
\nPresence of water soluble calcium and magnesium bicarbonate sulfates and chlorides cause hardness in water.<\/p>\n
\nSodium metal should be stored under Kerosene.
\nAnswer:
\nSodium is to be kept under kerosene as it can react with oxygen and water vapors present in air and kerosene has no affinity towards sodium.<\/p>\n
\nWashing soda loses its crystal structure quickly.
\nAnswer:
\nWashing soda loses its crystal structure quickly as it loses water when exposed to air of moderate humidity. It is efflorescent substance.<\/p>\n
\nWhen calcium nitrate crystals are exposed to air a solution is formed?
\nAnswer:
\nCalcium nitrate when exposed to air absorb moisture from the atmospheric air to become moist and dissolve in the absorbed water therefore it cannot be in the crystal form. It is deliquescent substance.<\/p>\nKSEEB Class 8 Science Chapter 13 Additional Questions & Answers<\/h3>\n
\nExplain the biological significance of water.
\nAnswer:
\nWater is one of the most abundant and important compounds in the world. It is the major constituent of all living organism, some plants contain more percentage of water, the human body has about 65% of water. Neither plants, animals nor human beings can survive without water.<\/p>\n
\nWater is called the universal solvent. Why?
\nAnswer:
\nWater is called the universal solvent because it dissolves more substance than any other solvent.<\/p>\n
\nWhat is the chemical formula of water?
\nAnswer:
\nThe chemical formula of water is H2<\/sub>O<\/p>\n
\nWrite the molecular structure of water molecule
\nAnswer:
\n![\"KSEEB](\"https:\/\/live.staticflickr.com\/65535\/48130595311_00304ff0f5_o.png\")
\nQuestion 5.
\nMany metals and their alloys are used to prepare utensils why?
\nAnswer:
\nMany metals and their alloys are used to prepare utensils because they do not react with water under normal conditions.<\/p>\n
\nWhat happens when potassium is dipped in water?
\nAnswer:
\nWhen potassium is dipped in water forming respective hydroxides liberating hydrogen gas.<\/p>\n
\nWhat happens when sodium is dipped in water?
\nAnswer:
\nSodium piece rushes here and there reacting with water violently. It gradually diminishes in size and finally disappears. It dissolves in water forming sodium hydroxide and hydrogen.<\/p>\n
\nWrite the equation for the reaction between potassium and water.
\nAnswer:
\n2k + 2H2<\/sub>O \u2192 \u00a02kOH + H2\u00a0<\/sub>\u2191<\/p>\n
\nRusting is quick in rainy season why?
\nAnswer:
\nRusting is quick in the rainy season because the humidity will be more in the rainy season, which promotes rusting..<\/p>\n
\nWhat happens when steam is passed over red hot metals like zinc, iron, magnesium. Write a balanced equation.
\nAnswer:
\nWhen steam is passed over red hot metals like zinc, iron, magnesium we get respective oxides and hydrogen gas.
\nZn + H2<\/sub>O \u2192 ZnO+ H2 <\/sub>\u2191
\n3Fe + 4H2<\/sub>O \u2192 Fe3<\/sub>O4<\/sub> + 4H2<\/sub>O \u2191
\nMg + H2<\/sub>O \u2192\u00a0 MgO+H2<\/sub> \u2191<\/p>\n
\nWhat happens when steam is passed over red hot coke and silicon.
\nAnswer:<\/p>\n\n
\nC + H2<\/sub>O \u2192 CO \u2191 + H2<\/sub>\u2191<\/li>\n
\nSi + 2H2<\/sub>O \u2192 SiO2\u00a0<\/sub> +2H2\u00a0<\/sub> \u2191<\/li>\n<\/ol>\n
\nWhat happens when carbon dioxide dissolves in water.
\nAnswer:
\nWhen carbon dioxide dissolves in water carbonic acid is formed.
\nCO2\u00a0<\/sub> + H2<\/sub>O \u2192 H2<\/sub>CO3 <\/sub>(Carbonic acid) Carbonic acid is present in soft drinks.<\/p>\n
\nWhat happens when calcium oxide reacts with water. Write a balanced equation.
\nAnswer:
\nWhen calcium oxide reacts with water it forms calcium hydroxide
\nCaO + H2<\/sub>O \u2192 Ca(OH)2\u00a0<\/sub><\/p>\n
\nGive some examples of the substances which can absorb moisture.
\nAnswer:
\nThe substances which absorb moisture are magnesium chloride, solid sodium hydroxide, solid potassium hydroxide, anhydrous calcium chloride, calcium nitrate Ferric chloride, and sodium nitrate.<\/p>\n
\nDefine deliquescence.
\nAnswer:
\nCertain water-soluble substances, when exposed to the atmosphere at ordinary temperature, absorb moisture from the atmospheric air to become moist and ultimately dissolved in the absorbed water. Such substances are called deliquescent substances.<\/p>\n
\nGive some examples of desiccants.
\nAnswer:
\nConcentrated sulfuric acid and calcium chloride monohydrate are examples for desiccants.<\/p>\n
\nDefine Efflorescent substances.
\nAnswer:
\nCertain hydrates that lose water when exposed to air of moderate humidity are called substances.<\/p>\n
\nGive an example of efflorescent substances.
\nAnswer:
\nSodium sulfate, (NaSO4<\/sub>10H2<\/sub>O) washing soda (Na2<\/sub>CO3<\/sub>H2<\/sub>O).<\/p>\n
\nCalcium carbonate does not cause hardness. Why?
\nAnswer:
\nCalcium carbonate does not cause hardness because it is insoluble in water.<\/p>\n
\nName the salts causing hardness in water.
\nAnswer:
\nCalcium and magnesium bicarbonates, sulfates, and chlorides cause hardness in water.<\/p>\n
\nWhat is meant by hard water?
\nAnswer:
\nThe water which does not give lather with soap is called hard water.<\/p>\n
\nWhat is meant by soft water?
\nAnswer:
\nThe water which gives lather readily with soap is called soft water.<\/p>\n
\nWhy is hard water not used in industrial boilers?
\nAnswer:
\nHard water contains calcium and magnesium soluble salts. If it is used in industrial boilers, it forms insoluble salts of calcium and magnesium. They produce scales on the inner walls of the boilers, which reduce heating efficiency. There is a chance of an explosion of boilers due to foaming. It also corrodes the boilers.<\/p>\n
\nMention methods of removal of hardness of the water.
\nAnswer:
\nHardness can be removed by two methods.<\/p>\n\n
\nCa (HCO3<\/sub>)2<\/sub> \u2192 CaCO3 <\/sub>+ H2<\/sub>O + CO2<\/sub>\u2191
\nMg (HCO3<\/sub>)2<\/sub>\u00a0\u2192 MgCO3<\/sub>+ H2<\/sub>O +\u00a0CO2<\/sub>\u2191<\/li>\n
\nCaCl2<\/sub>+ Na2<\/sub>CO3\u00a0 <\/sub> \u2192 CaCO3 <\/sub>+ 2NaCl\u00a0 \u2193
\nCaHCO3 <\/sub>+Na2<\/sub>CO3<\/sub> \u2192 CaCO3<\/sub>\u2193 + 2NaHCO3
\n<\/sub>CaSO4 <\/sub>+ Na2<\/sub>CO3<\/sub>\u00a0\u2192 CaCO + Na2<\/sub>SO4<\/sub><\/li>\n<\/ol>\n
\nExperiment to show the removal of hardness by washing soda.
\nAnswer:
\nMaterials required:<\/p>\n\n
\nWhat is meant by Desalinization?
\nAnswer:
\nDesalinization is an artificial process by which saline water (generally seawater) is converted into freshwater.<\/p>\n KSEEB Solutions for Class 8 Science<\/a><\/h4>\n","protected":false},"excerpt":{"rendered":"