Page 40 - Genius Kidz Prudence Learning Sc-8

(c) Spontaneous combustion : can be the room temperature on

(i) It is that type of combustion in which a normal hot day.
substance catches fire without even
being ignited.
(ii) This kind of combustion is characteristic

of those inflammable substances
whose ignition temperature is just
below the room temperature.

(iii) Example is burning of white
phosphorous when it is exposed to air;
as its ignition temperature is 35°C which
Three types of fire
Activity 1
Hold a class discussion on “How can fire be extinguished or on fire fighting”. Prepare notes in the space given.

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Designing of fire extinguisher :
plunger is fitted a test tube filled with concentrated sulphuric acid. This tube is protected by a wire gauze cage in
turn. Rest portion of the cylinder is filled with sodium bicarbonate solution and its top is scaled by wax scal.
Working :
Fire

Plunger hits up the tube as a result of which

Acid escapes out to react with sodium bicarbonate
2NaHCO + H SO ¾¾® Na SO + 2H O + 2CO
3 2 4 2 4 2 2

CO produced
2

It is directed towards the fire and CO extinguishes the fire.
2

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