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