0.8(I) What are the essential condition required for combustion?
(ii) What is the essential condition required for extinguishing fire?
Q.9 What are inflammable substance? Give examples.
Q.10 In what form is LPG stored in cylinders?
Q.11 Name the most common fire extinguisher?
Q.12 Water is not suitable for extinguishing fires involving electrical equipment oil and
petrol. Why?
Q.13 Explain how CO2 is able to control fires?
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Answers
8. i. Three things are required in proper combination before ignition and combustion can take place---Heat, Oxygen and Fuel. There must be Fuel to burn. There must be Air to supply oxygen. There must be Heat (ignition temperature) to start and continue the combustion process.
ii. Therefore, we can extinguish fire by cutting of supply of any one of the following ( Fuel, Oxygen. Heat ). For example, when fire takes place, we can extinguish it by spraying water.
9. The substances which have very low ignition temperature and can easily catch fire with a flame are called inflammable substances. Examples of inflammable substances are petrol, alcohol, Liquified Petroleum Gas (LPG), etc.
10. the gas is stored in liquid form under pressure in a steel container, cylinder or tank. The pressure inside the container will depend on the type of LPG and the outside temperature.
11. Water fire extinguishers are the most popular fire extinguisher type and they are suited to class A fire risks. ...
Foam fire extinguishers are the most common type of extinguisher used for Class B fires.
12. Water cannot put off fire produced due to burning petrol and oil because water is heavier than oil. It settles down or sinks below the oil particles and cannot bring the ignition temperature of the substance down or cannot cut off the supply of air to the fire. Hence, oil keeps on burning on the top.
13. Carbon dioxide is heavier than oxygen, covers the fire like a blanket. Since the contact between the fuel and oxygen is cut off, the fire is controlled. The added advantage of CO2 is that in most cases it does not harm the electrical equipment.
Answer:
For combustion to take place, we need a combustible substance. Oxygen, which supports combustion, is necessary for combustion.