Ncert – class 8- science – Chapter 4: Combustion and Flame 2 Welcome to your Ncert - class 8- science - Chapter 4: Combustion and Flame 2 1. Which of the following statements is true? Water extinguishes a fire in two ways: (1) It brings the temperature of the combustible material below its ignition temperature. (2) The water vapour formed due to the heat of fire cuts the supply of oxygen. None Carbon dioxide is highly volatile. So, it immediately vaporises to cut off the supply of air. In the absence of supporter of combustion, fire is extinguished. Both None 2. What is calorific value? Amount of heat energy consumed on complete combustion of 1 kg of fuel. Amount of heat energy produced on complete combustion of 1 kg of fuel. Amount of heat energy consumed on complete combustion of 1 g of fuel. Amount of heat energy produced on complete combustion of 100 kg of fuel. None 3. Which of the following is not true about combustion? In the absence of air candles flame flickers but does not goes off. In case of chimney when air does not enters from below, the flame flickers and produces smoke. In case of chimney when air does not enters from below, the candle burns freely. In case of chimney candle burns freely when air enters from below the chimney. None 4. Which of the following statement is not correct? Air is essential for the burning process The flame of a burning candle can be put off by placing a cover cap over the flame Burning of coal cannot be stopped by covering it with sand Burning of wood can be stopped by covering it with sand None 5. Shyam was cooking potato curry on a chulha. To his surprise, he observed that the copper vessel was getting blackened from outside. It may be due to: burning of copper vessel proper combustion of fuel improper cooking of potato curry improper combustion of the fuel None 6. Which of the following is not true about combustion? In case of chimney, candle burns freely when air enters from below the chimney. In the absence of air candles flame flickers but does not goes off. In case of chimney, when air does not enter from below, the flame flickers and produces smoke. In case of chimney, when air does not enter from below, the candle burns freely. None 7. Match column 'A' with column 'B', concerning the characteristics of a flame and its zones.'A''B'a. Dark inner zone1. Hottest part (No carbon)b. Blue zone2. Partial combustionc. Luminous zone3. Unburnt vapours of waxd. Non-luminous zone4. Complete combustion a - 4, b - 1, c - 2, d - 3 a - 3, b - 4, c - 2, d - 1 a -1, b - 2, c - 3, d - 4 a - 2, b - 3, c - 4, d - 1 None 8. Which type of fire extinguisher is used to extinguish fire caused by burning oil and petrol? Foam type Water type Soda acid type CCl4 type None 9. What kind of combustion is undergone by ignition of a cracker? Slow combustion Rapid combustion Spontaneous combustion Explosive combustion None 10. If you fix a burning candle on a petri dish, it will continue to burn, but when you put an inverted beaker over it, the flame goes off. Why does this happen? None The supply of oxygen is cut off. Both Insufficient nitrogen in the air. None 11. When paper is wrapped around an Aluminium pipe ____________. no change in ignition temperature ignition temperature reduces the paper and aluminium catches fire very easily ignition temperature increase None 12. Gasoline combusts in the presence of oxygen. Identify whether Combustion is a physical property or chemical property There is not enough information to tell if this is a physical or chemical property. This is a physical property. This is neither a physical nor a chemical property. This is a chemical property. None 13. Why are the spirit and kerosene lamps made in such a way that the free end of the wicks with the flame remains totally cut off from the fuel?i)The fuel vaporization in room temperature ii)The fuel is highly inflammable ii) The calorific value of fuel can be increased. Only (i) and (ii) Only (ii) and (iii) (i), (ii) and (iii) Only (i) and (iii) None 14. What is an ideal fuel? All of the above It is readily combustible. It has high calorific value. It is cheap. None 15. Combustion is a ________ reaction accompanied by heat and light. redox reduction oxidation substitution 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.
