Combustion And Flame Flashcards
List conditions under which combustion can take place.
There are three essential conditions of combustion:
* Presence of a combustible substance.
* The presence of oxygen
* Attainment of ignition temperature.
Explain how the use of CNG in automobiles will reduce pollution in our cities.
CNG is cheap, readily available, and highly combustible. It has high calorific value and does not produce harmful gases or leave residue when used in automobiles. So, it reduces the pollution in our cities. The use of CNG in automobiles has reduced pollution in our cities because CNG produces harmful chemicals in very small amounts and is a cleaner fuel.
Compare LPG and wood as fuels.
LPG:
LPG residue is not formed after burning.
It has a low ignition temperature.
It catches fire easily.
It burns without smoke.
It can be easily stored in cylinders for convenient transportation.
Wood:
A lot of ash is produced on burning.
It has a high ignition temperature.
It catches fire with more difficulty.
It burns with smoke.
It cannot be transported easily like LPG.
Describe the various zones of flame
A flame has three zones in it:
* The outermost, thin, transparent, faint, bluish, non-luminous region of complete combustion is the hottest zone of the flame.
* The middle, brightest, luminous zone of partial combustion is the moderately hot zone.
* The innermost, coldest, dark zone consists of hot vapour and is called the zone of no combustion.
The blue zone near the bottom of the flame is due to the burning of carbon monoxide. Carbon monoxide is formed due to incomplete combustion.
Name the unit in which the calorific value of a fuel is expressed. Define calorific value.
The calorific value of a fuel is the amount of heat energy produced on complete combustion of 1 kg of fuel. It is expressed in terms of kilojoule per kg (kJ/kg).
Define Combustion. Explain various types of combustion.
A chemical process in which a substance reacts with oxygen to give off heat. The following are the types of combustion:
Rapid Combustion: A combustion that takes place rapidly or at high speed with the production of heat and light is called Rapid Combustion.
Example: Lighting a matchstick.
Spontaneous Combustion: A combustion in which a material burns into flames without the application of any apparent cause is called Spontaneous Combustion.
Example: A pile of oily rags catching fire on their own.
Explosion: The process of combustion in which a large amount of gases are evolved with the production of a large amount of heat, light, and sound is called an explosion.
Example: A firecracker bursting when lit.
Explain how CO2 is able to control fires.
Carbon Dioxide (CO2), being heavier than oxygen, covers the fire like a blanket and also brings down the temperature of the fuel. Since the contact between the fuels is cut off, the fire comes under control.
What are the different harmful products formed by burning of fuel?
The different harmful products formed by burning of fuel are Carbon Dioxide (CO2), Carbon Monoxide (CO), Nitrogen Oxide (NOx), Sulfur Dioxide (SO2), etc.
Why is CNG preferable in vehicles with respect to diesel and petrol?
CNG (Compressed Natural Gas) is often preferred over petrol and diesel due to its lower emissions of harmful pollutants and greenhouse gases. It produces less CO2, NOx, contributing to better air quality and reducing environmental impact.
Can the process of rusting be called combustion?
The process of rusting can not be called combustion because neither any heat nor light is produced while in combustion, and the release of energy takes place with heat and light.
Although wood has a very high calorific value, we still discourage its use as a fuel. Explain.
Wood’s high calorific value is outweighed by deforestation, air pollution, and inefficiency compared to cleaner, more sustainable fuels.
Why is water not used to control fires involving electrical equipment?
Water is not used to control fires involving electrical equipment because it is a good conductor of electricity. Using water could result in electric shock to the person attempting to control the fire.
Why is LPG a better domestic fuel than wood?
LPG is a better domestic fuel than wood because it does not produce harmful gases and does not leave any residue that can pollute the environment.
What is global warming?
The combustion of fuels releases carbon dioxide into the atmosphere. When the percentage of carbon dioxide increases, it traps heat and raises the temperature of the earth’s surface, leading to global warming.
What is acid rain?
Gases like nitrogen oxide (NOx) and sulfur dioxide (SO₂) are present in the atmosphere as pollutants. When these gases dissolve in rainwater, they form acids. When this acidic rainwater reaches the earth, it is called acid rain.
