Combustion and Flame

Combustion

• Combustion is a chemical reaction where heat gets released through a material when it gets reacted with oxygen.
• A combustible substance is one which undergoes combustion.
• Combustible substance is also known as fuel
• It may be in the form of solid, liquid, or gas.

Ignition temperature

• It is the minimum temperature at which the clothes of any material catch fire.
• The ignition temperature has to be higher than the temperature of the combustible substance for the substance to get burn.

Inflammable substances

• Inflammable substance easily catches fire as they have low ignition temperature.
• For example – LPG, petrol, etc.

Things necessary for combustion to take place

• Fuel
• Temperature
• Air

Measures to control fire

1. Fire brigade stations

• These stations cool down the fire by sprinkling water on the areas affected.
• The water sprinkled brings down the temperature below the ignition.

2. Fire extinguisher

• The most common fire extinguisher is water which works on paper, wood, etc.
• In cases of fire due to oil, petrol, water is not good; in this case Carbon dioxide is used as an extinguisher.

3. Use of blankets

• Blankets can also be used as a fire extinguisher.

Different types of combustion

1. Rapid combustion

• The substances catch fire easily and burn very fast. They also yield heat and light.

2. Spontaneous combustion

• Suddenly the substances get into the flames without any specific reason in a spontaneous combustion.

3. Explosion

• Reaction in this type of combustion suddenly results into light, heat, and sound.

4. Flame

• When substances vaporize on heating, flames get generated.

Fuel

• Fuel is a substance that undergoes the process of combustion.
• Examples are charcoal, petrol, wood, kerosene, etc.

Characteristics of a good fuel

• It has to be cheap
• It should be quite simply available.
• Large amount of heat should get generated.
• After combustion, any unwanted matter should not be left behind.

Fuel efficiency

• Calorific value is the amount of heat generated on combustion of around 1 kg of a fuel.
• The unit is kilojoule per kg (kj / kg)

Harmful effects of burning fuel

• Various carbon particles get released in the air causing respiratory diseases.
• Global warming
• Acid rain

Recap

• Combustion is a chemical reaction where heat gets released through a material when it gets reacted with oxygen.
• A combustible substance is one which undergoes combustion.
• It is the minimum temperature at which the clothes of any material catch fire.
• Fuel is a substance that undergoes the process of combustion.
• Examples are charcoal, petrol, wood, kerosene, etc.
• Calorific value is the amount of heat generated on combustion of around 1 kg of a fuel.
• The unit is kilojoule per kg (kj / kg).