Multiple choice

Water is not effective in extinguishing a fire caused by petrol because

  1. the flames are too hot for water to cool it down

  2. water and petrol react chemically

  3. water and petrol are miscible with each other

  4. water and petrol are immiscible with each other and petrol which forms the upper layer continues to burn
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Petrol floats on water because it is less dense, and water cannot mix with petrol as they are immiscible liquids. When water is poured on burning petrol, it settles below and the petrol continues to burn on the surface, actually spreading the fire further. Water cools by evaporation, but this effect is overwhelmed by the floating fuel layer continuing to burn.

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