Ncert – class 8- science – Chapter 4: Combustion and Flame 1 Welcome to your Ncert - class 8- science - Chapter 4: Combustion and Flame 1 1. Which chemical substance is emitted in car exhaust and is a cause of acid rain? Lead DDT Nitrogen oxides Carbon dioxide None 2. A thin paper cup filled with water does not catch fire when placed over a flame. This is because: water is an excellent conductor of heat paper is a poor conductor of heat the paper cup does not reach to ignition temperature the water cuts off oxygen supply to the paper cup None 3. When fuel is added to the exhaust (burnt) gases in a jet engine combustion takes place. Some facts are mentioned here about this combustion. Pick the false one? It gives additional thrust It is known as 'after burning' It reduces fuel consumption It increases the intake of oxygen from the air None 4. The cooking gas burns rapidly and produces heat and light. Such combustion is called _________. none of these incomplete combustion rapid combustion regular combustion None 5. Fire extinguishers containing CO2 are the best extinguishers for fires involving electrical equipment: because CO2 being heavier than oxygen increases fire. because CO2 being lighter than oxygen covers the fire like a blanket. None of these because CO 2 being heavier than oxygen covers the fire like a blanket. None 6. The heat liberated per kilogram of a fuel is called its: calorific value weight value fuel value mass value None 7. Which of the following are the characteristics of Indian coal?1. High ash content2. Low sulphur content3. High sulphur contentSelect the correct answer using the codes given. 2 only 1 and 3 only 1 and 2 only 1,2, and 3 None 8. For complete combustion of a fuel, it will need: an excess of air and high temperature an excess of air high air pressure high temperature None 9. Explosion of crackers takes place due to application of _________ on them. pressure temperature none of these heat None 10. I. The most significant way in which humans are exposed to mercury is through drinking water.��II. A great deal of mercury enters the atmosphere because of coal-burning power plants. Statement I is false, Statement II is true Statement I is true, Statement II is true Statement I is true, Statement II is false Statement I is true, Statement II is true and is a correct explanation of the phenomena described in I None 11. Which of the following examples represents explosion? Ignition of a cracker Burning of phosphorus in air at room temperature Burning of cooking gas Burning of matchstick None 12. How water helps in extinguishing fire? Water cools the combustible material so that its temperature is brought below the ignition temperature. None of these Water heats the combustible material so that its temperature is brought below the ignition temperature. Water cools the combustible material so that its temperature is brought above the ignition temperature. None 13. Which compound is formed due to incomplete combination of fuels? Carbon monoxide Oxygen Water Carbon dioxide None 14. During burning of candle, different zones of combustion in the flame are listed below:-a) Outermost zoneb) Innermost zonec) Middle zone The correct order of temperature of zones is : C>B>A B>C>A A>B>C A>C>B None 15. If you watch a burning candle carefully, you will find different colurs in the flame. Which is the hottest part of the candle flame? The outermost portion that is blue The middle, yellow part The innermost black zone The middle orange part None 16. What reactant must be present for a reaction to be classified as combustion? O2 Cl4 CO CH4 None 17. Which of the following happen when a wax candle is burnt(i) Fuel undergo oxidation(ii)Liberation of heat and light energy (iii) release of water vapour and carbondioxide (i), (ii) and (iii) (iii) and (i) only (i) and (ii) only (ii) and (iii) only None 18. A white solid X reacts with dil.HCl to give colourless gas which is used in fire extinguishers. The solid X is: NaCl $$Na_{2}Co_{3}$$ $$CH_{3}COONa$$ NaHCO3 None 19. Which of the following example represents spontaneous combustion? Burning of matchstick. Ignition of a cracker. Phosphorus burns in air at room temperature Burning of cooking gas. None 20. How carbon dioxide is stored in the house to extinguish fire? It can store in the cylinders under high pressure It can store in canes It can not store in any form It can store in the bottles None Time's up Please Share This Share this content Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Leave a Reply Cancel replyCommentEnter your name or username to commentEnter your email address to commentEnter your website URL (optional) Save my name, email, and website in this browser for the next time I comment.
