Question

17. Give reasons:

(a) Methane burns with blue flame
(b) Vegetable oils decolourize bromine water.
(c)Air holes of a gas burner has to be adjusted when heated vessels get blackened by the flame.​

Answer 1

1. Methane is a natural gas. Complete combustion creates enough energy to excite and ionise the gas molecules in the flame.
2. The chemical reason behind this phenomenon is,there are unsaturated hydrocarbons present in the cooking oil, that's why it decolourise the normal bromine water.
3. Air holes is the place from where gas comes and and leads to burning of flame when these holes gets damaged then the passage of the gas gets blocked which in leads to inadequate burning leading to blackened vessel.

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