Question

Why is phosphorus placed in water?

Answer 1

phophorus is explosive in nature so it is kept in karosinn

Answer 2

White Phosphorous catches fire by just coming in contact with Oxygen and gives white fume of P4O10.

BUT but but. the interesting fact is that it catches fire in just 30°C which is nearly equal to room temperature.

So never try to keep it in your pocket..

hoping helps you