Weekend assignment for 8th std students. Sub:Science. Answer the following briefly. 1) Why do we use gold and silver for making jewellery? 2) Explain why bells are made of metals or their alloys but not of wood? 3) Why do we polish metals to bring back their shine? 4) Why are wires made of metals like aluminium or copper and not of carbon or Sulphur? 5) Silver is used to very thin foils which are used to decorate sweets. explain. **********************
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Answer:
) Platinum, gold and silver are used to make jewellery because these are low reactive metals. So they rarely corrode and hence do not lose their shine and lustre.
) Platinum, gold and silver are used to make jewellery because these are low reactive metals. So they rarely corrode and hence do not lose their shine and lustre.(b) The reaction of these substances with oxygen is highly exothermic which may cause fire, also they react with water to form base so they are kept in oil.
) Platinum, gold and silver are used to make jewellery because these are low reactive metals. So they rarely corrode and hence do not lose their shine and lustre.(b) The reaction of these substances with oxygen is highly exothermic which may cause fire, also they react with water to form base so they are kept in oil.(c) This is because aluminium is good conductor of heat and electricity. To prevent its reaction with food at high temperature a protective layer of aluminium oxide (Al
) Platinum, gold and silver are used to make jewellery because these are low reactive metals. So they rarely corrode and hence do not lose their shine and lustre.(b) The reaction of these substances with oxygen is highly exothermic which may cause fire, also they react with water to form base so they are kept in oil.(c) This is because aluminium is good conductor of heat and electricity. To prevent its reaction with food at high temperature a protective layer of aluminium oxide (Al 2
) Platinum, gold and silver are used to make jewellery because these are low reactive metals. So they rarely corrode and hence do not lose their shine and lustre.(b) The reaction of these substances with oxygen is highly exothermic which may cause fire, also they react with water to form base so they are kept in oil.(c) This is because aluminium is good conductor of heat and electricity. To prevent its reaction with food at high temperature a protective layer of aluminium oxide (Al 2
) Platinum, gold and silver are used to make jewellery because these are low reactive metals. So they rarely corrode and hence do not lose their shine and lustre.(b) The reaction of these substances with oxygen is highly exothermic which may cause fire, also they react with water to form base so they are kept in oil.(c) This is because aluminium is good conductor of heat and electricity. To prevent its reaction with food at high temperature a protective layer of aluminium oxide (Al 2 O
) Platinum, gold and silver are used to make jewellery because these are low reactive metals. So they rarely corrode and hence do not lose their shine and lustre.(b) The reaction of these substances with oxygen is highly exothermic which may cause fire, also they react with water to form base so they are kept in oil.(c) This is because aluminium is good conductor of heat and electricity. To prevent its reaction with food at high temperature a protective layer of aluminium oxide (Al 2 O 3
) Platinum, gold and silver are used to make jewellery because these are low reactive metals. So they rarely corrode and hence do not lose their shine and lustre.(b) The reaction of these substances with oxygen is highly exothermic which may cause fire, also they react with water to form base so they are kept in oil.(c) This is because aluminium is good conductor of heat and electricity. To prevent its reaction with food at high temperature a protective layer of aluminium oxide (Al 2 O 3
) Platinum, gold and silver are used to make jewellery because these are low reactive metals. So they rarely corrode and hence do not lose their shine and lustre.(b) The reaction of these substances with oxygen is highly exothermic which may cause fire, also they react with water to form base so they are kept in oil.(c) This is because aluminium is good conductor of heat and electricity. To prevent its reaction with food at high temperature a protective layer of aluminium oxide (Al 2 O 3 ) is formed which prevent further corrosion.
) Platinum, gold and silver are used to make jewellery because these are low reactive metals. So they rarely corrode and hence do not lose their shine and lustre.(b) The reaction of these substances with oxygen is highly exothermic which may cause fire, also they react with water to form base so they are kept in oil.(c) This is because aluminium is good conductor of heat and electricity. To prevent its reaction with food at high temperature a protective layer of aluminium oxide (Al 2 O 3 ) is formed which prevent further corrosion.(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction because it is easier to obtain metal from its oxide as compared with its sulphides or carbonates ore.
Answer:
The 2021 Uttarakhand flood began on 7 February 2021 in the environs of the Nanda Devi National Park, a UNESCO World Heritage Site[1] in the outer Garhwal Himalayas in Uttarakhand state, India (Maps 1 and 2).[2] It is believed to have been caused by a landslide, an avalanche or a glacial lake outburst flood.[3] It has caused flooding in the Chamoli district, most notably in the Rishiganga river, the Dhauliganga river, and in turn the Alaknanda—the major headstream of the Ganges (Maps 2 and 3).[4][5] At least 72 people are confirmed to have been killed.[6]
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