Question

Which of the following definition(s) related to fire and explosion is/are CORRECT?

• A. Fire point is the lowest temperature at which the vapour above a liquid will continue to burn once ignited.
• B. Deflagration is the explosion in which the reaction front moves at a speed greater than the speed of sound in the unreacted medium.
• C. Detonation is the explosion in which the reaction front moves at a speed less than the speed of sound in the unreacted medium.
• D. Flash point of a liquid is the lowest temperature at which it gives enough vapour to form an ignitable mixture with air.

Hint:

Remember: Flash point → vapour ignites but may not sustain. Fire point → vapour sustains combustion. Deflagration = subsonic, Detonation = supersonic.

Answer 1

The Correct Option is A, D

Step 1: Fire point.
- The fire point is correctly defined as the lowest temperature at which vapours above a liquid will continue to burn once ignited. 

- Hence, (A) is correct. 

Step 2: Deflagration vs Detonation.
- Deflagration is a subsonic combustion process: the reaction front moves at a speed less than the speed of sound. 

- Detonation is supersonic combustion: the reaction front moves at a speed greater than the speed of sound. 

- Therefore, statements (B) and (C) are incorrect because they are swapped.

Step 3: Flash point.
- The flash point is the lowest temperature at which a liquid gives off sufficient vapour to form an ignitable mixture with air. 

- This is correctly stated in (D). 

Final Answer: \[ \boxed{(A) \text{ and } (D)} \]