32 Manu was heating oil to fry potato chips. Fire Fighting Phases: Do not use water or halogenated hydrocarbons such as carbon tetrachloride. (d) Calorific value of wood is higher than that of coal. (e) The substances which have very low……………… temperature and can easily catch fire with a flame are called…………….. substances. Each year in the United States 70 - 80,000 workplaces experience a fire. 8 The substance expected to have the highest ignition temperature out of the following is Also write the false statements in their correct form. Nitrogen cylinders that comply with 49 CFR 173.34(e)(15) may be hydrostatically tested every 10 … Carbon dioxide, ordinary(BC-rated)dry chemical, multi-purpose dry chemical and halon* fire extinguishers may be used to fight Class C fires. A "rest area" expansion chamber in a liquid flow line permits static electricity to bleed off. PAST b. 3. True b. (d) Some substances on combustion produce thea and mafel. Answer. You can recognize a CO2 extinguisher by its hard horn and lack of pressure gauge. c. Use the. It only glows on combustion. MCQ Questions for Class 8 Science with Answers were prepared based on the latest exam pattern. Question. (c) low ignition temperature and can catch fire easily to 20 lbs. 1.Combustible — charcoal, straw, cardboard, paper, candle, wood. (e) The substances which vaporise during……………..give flame. Carbon dioxide can be used on Class B & C fires. It means that if 1 kg of LPG is burnt completely, then it will produce 55000 kilojoules of heat energy. 13 Which one among the following is considered as the cleanest fuel? 3 Magnesium ribbon on burning in air produces To his surprise, he observed that the copper vessel was getting blackened from outside. (d) Charcoal is a solid fuel which does not vaporise on heating. (d) Calorific value of wood is higher than that of coal. In jar B, the candle remains lighted for a longer time because oxygen is a supporter of combustion. 31 You are provided with three watch glasses containing milk, petrol and mustard oil respectively. We will prefer CNG (Compressed Natural Gas) because the calorific value of CNG is higher than that of petrol. We hope the NCERT Exemplar Class 8 Science Chapter 6 Combustion and Flame help you. It is recommended that carbon dioxide fire extinguishers be installed in pairs. (a) Camphor (b) Glass (c) Straw (d) Alcohol (c) improper combustion of fuel (d) burning of copper vessel (a) Air is necessary for combustion. ), or otherwise requires the expertise of a fire brigade. (c) Carbon dioxide is an excellent fire extinguisher. Answer. 11. (4) It causes suffocation in a closed room. Cloudflare Ray ID: 6147408399512c2a It is a solid fuel and produces smoke during combustion. (c) Inflammable substances have low ignition temperature and can catch fire easily. Question. When using a fire extinguisher you should use the PASS procedure. Asked by Wiki User. 2. Overview: CO2 extinguishers are predominantly used for electrical fire risks and are usually the main fire extinguisher type provided in computer server rooms. Answer. CO2 (Carbon Dioxide) Fire Extinguishers contain only pressurised CO2 gas and therefore leave no residue. (a)—(iv), (b)-(vi), (c)-(v), (d)—(iii), (e)-(i), (f)-(ii), Question. (c) Magnesium ribbon on burning in air produces magnesium oxide, heat and light, Magnesium ribbon is a very reactive metal. So, Manu should have switched off the flame of the burner and put a lid on the frying pan. 16 Fill in the blanks. a. Answer. (iii) Trees provide us many-useful substances. Burning of wood has several disadvantages. Water is ineffective as it helps to spread the liquid and the fire. a. true b. false ref. True or False 17. Answer. (d) The substances which gave very …………..ignition temperature and can easily catch fire with a flame are called………….substances. In such a condition what should Manu have done? (d) Wood is a combustible substance. 3. Question. d. All of the above. 25 If you hold a piece of iron wire with a pair of tongs inside a candle flame or a Bunsen burner flame, what will you observe? In a soda-acid type fire extinguisher, _____reacts with sulphuric acid to give out carbon dioxide. Answer. (c) Chittsmack does not burn by itself. (b) False, carbon dioxide is the best extinguisher for fires involving electrical equipment. (a) magnesium oxide, water and light (b) magnesium oxide and heat 22 State whether the following statements are True/False. For fires involving electrical equipment and inflammable materials like petrol, then carbon dioxide (C02)is the best extinguisher. Solid fuels Examples are wood and coal. Answer. True or False? They cut off the supply of air to the fire. Carbon dioxide (CO2) extinguishers contain carbon dioxide forced into its liquid state by pressure. Carbon Dioxide fire extinguisher works by displacing oxygen from the fire triangle. (8) You may need to download version 2.0 now from the Chrome Web Store. Carbon dioxide extinguishes fire by displacing oxygen or by taking away oxygen from the fire triangle. 12. (c) magnesium oxide, heat and light (d) magnesium oxide, water and heat In the outer zone of a flame, complete combustion of the fuel takes place because there is plenty of air around it so, water in a test tube will boil quickly in this zone. It occurs naturally in Earth's atmosphere as a trace gas.The current concentration is about 0.04% (412 ppm) by volume, having risen from pre-industrial levels of 280 ppm. Answer. Carbon dioxide extinguishers are best used for electric (E) fires. (c) Kerosene (d) Hydrogen gas Carbon Dioxide based fire extinguishers remove what from the fire? In such situations, soda-acid fire extinguisher does not work as it contains water or uses water to take off fire by cooling down the place. 6 On placing an inverted tumbler over a burning candle, the flame extinguishes after some time. Answer. Reasons of forest fires are : True 12 Class B fires can be extinguished with water, water based agents, and dry chemicals. Indicate whether the following statements are True or False. By doing this, the contact between fuel and oxygen is cut off and the flame will go off. CO2 fire extinguishers remove the heat element of the fire, as well as reducing the oxygen to the fire. Oxygen. The job of fire extinguisher is to cut off the supply of air or to bring down the temperature of fuel or both. (a) low ignition temperature and cannot catch fire easily (iv) The use of fires by villagers to ward off wild animals. 2011-11-02 01:11:10 2011-11-02 01:11:10. True or false? Ignition 5. (c) Coal has the highest ignition temperature. 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