Combustion and flame Worksheet-3

Combustion and flame Worksheet-3

Multiple Choice Questions:

11. Which one of the following is non Combustible?

A. Stone piece                                B. Paper

C. Straw                                          D. Matchsticks

12. We can boil water in a paper cup without cup being burnt because ______

A. Ignition temperature of paper is not reached in the presence of water

B. Water decreases the temperature of paper thus paper doesn’t burn

C. The heat supplied to the paper cup is transferred to water by conduction. So paper doesn’t burn.

D. All of these

13. Which of the following has least ignition temperature?

A. Petrol             B. Wood             C. Paper             D. Straw

14. Essential requirements for producing fire are:

A. Fuel                                            B. Air

C. Heat                                            D. All of these

15. Fire extinguishers extinguish fire by _______.

A. Cutting off the supply of air

B. Bring down the temperature of fuel

C. Cutting off the supply of air & bringing down the temperature of fuel

D. None of these

16. Rapid combustion is ______.

A. When a substance burns releasing a large amount of heat and light in short span of time

B. When a substance suddenly bursts into flames

C. When a substance burns with the evolution of heat, light and sound

D. None of these

17. Soda-acid fire extinguisher contains-

A. Concentrated solution of sodium hydrogen carbonate and sulphuric acid in separate compartments

B. Concentrated solution of potassium hydrogen carbonate and sulphuric acid in separate compartments

C. Concentrated solution of sodium carbonate and sulphuric acid in separate compartments

D. Concentrated solution of sodium hydrogen carbonate and sulphurous acid in separate compartments

18. Substance which vaporise during Burning gives______.

A. Sound                                         B. Flame

C. Combustion                              D. None of these

Which is the hottest part in the flame of the candle?

A. Wax part      B. Yellow           C. Black             D. Blue

20. Innermost zone is the _____.

A. Hottest part                              B. Moderately hot part

C. Least hot part                           D. Cold part

Answer:

11. A

12. A

Explanation: The heat supplied to the paper cup is transferred to water by conduction. So, in the presence of water, the ignition temperature of paper is not reached. Hence, it does not burn

13. A

14. D

The three essential conditions for producing fire.

15. C

Explanation: In fire extinguishers carbon dioxide gas is filled under high pressure. The pressure in the cylinder is so high that when it is used bits of dry ice (solid CO₂) may shoot out.

Carbon dioxide extinguishes fire by forming a blanket over fire thus cutting off the supply of oxygen. The carbon dioxide is also very cold as it comes out of the extinguisher, so it cools the fuel as well.

16. A

17. A

Explanation: Soda-acid fire extinguisher contains concentrated solution of sodium hydrogen carbonate and sulphuric acid in separate compartments. When the fire extinguisher is used, the two substances come into contact with each other, producing carbon dioxide. Carbon dioxide produced is sprayed over fire thus extinguishing it.

18. B

Explanation: Flame is the zone of combustion of a combustible substance. Substances which vapourise during burning produce flames.

19. B

Explanation: A blue flame is also called a non-luminous flame as it emits very little light. A blue flame is generally observed when there is adequate amount of oxygen available (i.e., complete combustion). This flame is the hottest. This type of flame leaves behind no residue.

20. C