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 produced on complete combustion of 100 kg of fuel. 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. None 3. Which of the following statement is not correct? Burning of wood can be stopped by covering it with sand Air is essential for the burning process Burning of coal cannot be stopped by covering it with sand The flame of a burning candle can be put off by placing a cover cap over the flame None 4. 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 (iii) Only (i) and (ii) Only (ii) and (iii) (i), (ii) and (iii) None 5. 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? The supply of oxygen is cut off. Insufficient nitrogen in the air. None Both None 6. Which type of fire extinguisher is used to extinguish fire caused by burning oil and petrol? Foam type Soda acid type CCl4 type Water type None 7. When paper is wrapped around an Aluminium pipe ____________. ignition temperature reduces the paper and aluminium catches fire very easily ignition temperature increase no change in ignition temperature None 8. Combustion is a ________ reaction accompanied by heat and light. redox substitution reduction oxidation None 9. 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 enter from below, the flame flickers and produces smoke. In case of chimney, when air does not enter from below, the candle burns freely. In case of chimney, candle burns freely when air enters from below the chimney. None 10. What is an ideal fuel? It is cheap. All of the above It is readily combustible. It has high calorific value. None 11. Gasoline combusts in the presence of oxygen. Identify whether Combustion is a physical property or chemical property This is a chemical property. This is a physical property. There is not enough information to tell if this is a physical or chemical property. This is neither a physical nor a chemical property. None 12. 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 - 2, b - 3, c - 4, d - 1 a -1, b - 2, c - 3, d - 4 a - 3, b - 4, c - 2, d - 1 a - 4, b - 1, c - 2, d - 3 None 13. What kind of combustion is undergone by ignition of a cracker? Spontaneous combustion Rapid combustion Explosive combustion Slow combustion None 14. Which of the following is not true about combustion? In case of chimney candle burns freely when air enters from below the chimney. 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 the absence of air candles flame flickers but does not goes off. None 15. 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: proper combustion of fuel improper combustion of the fuel improper cooking of potato curry burning of copper vessel 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.
