The correct option is (c).
Explanation
A flame is the visible, gaseous part of a fire. It is caused by a highly exothermic reaction (combustion) taking place in a thin zone. A typical candle flame consists of three main zones based on the availability of oxygen and the extent of combustion: the innermost zone, the middle zone, and the outermost zone.
Statement-wise Analysis:
- Statement 1 is Correct: The blue zone represents the area of complete combustion. In this zone, the fuel vapors receive a sufficient supply of oxygen from the surrounding air, allowing them to burn completely, resulting in a blue, non-luminous flame.
- Statement 2 is Incorrect: The blue zone is the hottest part of the flame, not the moderately hot part. The complete combustion releases the maximum amount of heat energy. The middle zone (luminous yellow zone) is the region of partial combustion and is considered moderately hot.
- Statement 3 is Correct: The blue zone is the outermost zone of the flame. It surrounds the inner zones and is in direct contact with atmospheric oxygen, facilitating complete oxidation.
Key Takeaway:
The outermost zone of a flame is blue, non-luminous, undergoes complete combustion, and is the hottest region. The middle zone is yellow, luminous, undergoes partial combustion, and is moderately hot.