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AnswerĪ goldsmith use the middle zone of a flame for melting gold, and silver. Wildlife and minerals are exhaustible natural resources. In the sun heat and light are produced by nuclear reactions. Water can be used to control fires involving electric equipment or oils. Answerĭecreased percentage of carbon dioxide in air has been linked to global warming. Unburnt carbon particles in air are dangerous pollutants causing respiratory problems. State whether the following statements are True or False: (iii) The lowest temperature at which a combustible substance catches fire. (ii) Substances having very low ignition temperature. (iii) When a material suddenly bursts into flames, without, the application of any apparent cause (ii) When gas burns rapidly and produces heat and light. (i) When a sudden reaction takes place with the evolution of heat, light, sound and large amount of gas. Which of the following give us pollution free environment on burning:īiogas gives us pollution free environment on burning.
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The poisonous gas formed as a result of incomplete combustion is carbon monoxide. Which poisonous gas is formed as a result of incomplete combustion ? LPG is smoke free fuel, wood, charcoal and coal produces smoke on burning. Which of the following is smoke free fuel: The conditions under which combustion takes place is the presence of a combustible substance, air with sufficient amount of oxygen and ignition temperature of the combustible substance. (d) all the above conditions are necessary (d) all the above conditions are necessary Answer (c) the temperature of combustible substance should be more than its ignition temperature (b) the presence of air with sufficient amount of oxygen (a) the presence of a combustible substance In which of the following conditions combustion takes place: Matchstick, straw and charcoal are combustible. Which of the following substance is not combustible: Magnesium bums in air to form magnesium oxide, heat and light. The hottest zone of candle flame is outermost zone.Ī chemical process in which a substance reacts with oxygen to give off heat is called.Ĭombustion is a chemical process in which a substance reacts with oxygen to give off heat.Ĭandle burns with a flame, coal, cow dung does not burn with a flame. The unit of calorific value is Kilojoules per kg. Which of the following causes global warming: Which of the following is best fuel for automobiles:ĬNG is best fuel for automobiles as it produces pollutants in very small amounts. LPQ paper and kerosene produces flame on burning whereas charcoal does not produce flame on burning. Which of following does not produce flame on burning: The fuel which replaces use of diesel and petrol as fuels in automobiles is:ĬNG has replaced use of diesel and petrol as fuels in automobiles because it is non-pollutant fuel. Petrol has higher calorific value than petrol. Which of the following fuel has the highest calorific value: The colour of the non-luminous zone is blue. The coldest zone of candle is the innermost zone. Which of the following gas extinguishes fire:Ĭombustion that takes place at a very fast rate is called:Ĭombustion that takes place at a very fast rate is called rapid combustion. (c) ignition temperature is same as room temperatureĪ matchstick does not catch fire on its own at room temperature because its ignition temperature is more than room temperature. (b) ignition temperature is less than room temperature (a) ignition temperature is more than room temperature Straw can be easily burnt with the help of a matchstick because the ignition temperature of straw is very less and heat produced from lighted matchstick is more than the ignition temperature of straw and therefore it starts burning.Ī mgtchstjck does not catch fire on its own at room temperature because its: Which of them can be easily burnt with the help of a matchstick? Ignition temperature is the lowest temperature at which a substance catches fire (c) lowest temperature at which a substance catches fire (b) highest temperature at which a substance catches fire (a) temperature at which a substance catches fire Heat and light produced in the sun is by nuclear reactions. Heat and light produced in the sun is by: No, heat and light produced by sun is not a combustion process. Is heat and light produced by Sun a combustion process? Yes, the process of rusting can be called combustion because it produces heat. The zone of a flame used by goldsmith for melting gold and silver is outermost zone because it is the hottest zone.Ĭan the process of rusting he called combustion ? The zone of a flame used by goldsmith for melting gold and silver is:
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Which of the following fuel produces ash on burning: