Ncert – class 8- science – Chapter 4: Combustion and Flame 1 Welcome to your Ncert - class 8- science - Chapter 4: Combustion and Flame 1 1. The heat liberated per kilogram of a fuel is called its: fuel value weight value calorific value mass value None 2. 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 (ii) and (iii) only (i), (ii) and (iii) (iii) and (i) only (i) and (ii) only None 3. 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 true and is a correct explanation of the phenomena described in I Statement I is true, Statement II is false None 4. 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 store in the bottles It can not store in any form None 5. A thin paper cup filled with water does not catch fire when placed over a flame. This is because: paper is a poor conductor of heat the water cuts off oxygen supply to the paper cup the paper cup does not reach to ignition temperature water is an excellent conductor of heat None 6. The cooking gas burns rapidly and produces heat and light. Such combustion is called _________. incomplete combustion regular combustion none of these rapid combustion None 7. Which of the following example represents spontaneous combustion? Phosphorus burns in air at room temperature Burning of matchstick. Ignition of a cracker. Burning of cooking gas. None 8. Fire extinguishers containing CO2 are the best extinguishers for fires involving electrical equipment: None of these because CO2 being lighter than oxygen covers the fire like a blanket. because CO 2 being heavier than oxygen covers the fire like a blanket. because CO2 being heavier than oxygen increases fire. None 9. A white solid X reacts with dil.HCl to give colourless gas which is used in fire extinguishers. The solid X is: NaHCO3 $$Na_{2}Co_{3}$$ NaCl $$CH_{3}COONa$$ None 10. Explosion of crackers takes place due to application of _________ on them. pressure none of these temperature heat None 11. 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 innermost black zone The middle, yellow part The middle orange part None 12. What reactant must be present for a reaction to be classified as combustion? Cl4 CH4 O2 CO None 13. Which chemical substance is emitted in car exhaust and is a cause of acid rain? Nitrogen oxides Lead DDT Carbon dioxide None 14. Which of the following examples represents explosion? Burning of matchstick Ignition of a cracker Burning of cooking gas Burning of phosphorus in air at room temperature None 15. For complete combustion of a fuel, it will need: an excess of air high air pressure an excess of air and high temperature high temperature None 16. Which compound is formed due to incomplete combination of fuels? Water Carbon dioxide Oxygen Carbon monoxide None 17. 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 increases the intake of oxygen from the air It is known as 'after burning' It reduces fuel consumption None 18. 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 A>C>B B>C>A A>B>C None 19. How water helps in extinguishing fire? None of these Water cools the combustible material so that its temperature is brought above the ignition temperature. Water cools the combustible material so that its temperature is brought below the ignition temperature. Water heats the combustible material so that its temperature is brought below the ignition temperature. None 20. 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. 1,2, and 3 1 and 3 only 2 only 1 and 2 only 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.
