Chemistry: Combustion Process

Combustion Process

• Combustion is a chemical reaction involving the reaction of a combustible substance with oxygen
• Produces heat and light energy, along with different products
• Can occur in various forms, such as flames or just glowing (heat energy)

Types of Combustion

• Rapid combustion: occurs quickly and typically with the help of an external source of heat or energy
• Spontaneous combustion: occurs without the need for an external source of ignition, such as when certain reactive substances come into contact with oxygen
• Explosive combustion: occurs rapidly and with the release of heat, light, and sound energy

Fire Triangle

• Consists of three essential elements for combustion: fuel, heat, and oxygen
• Removing any one of these elements can stop the fire from continuing

Fire Extinguishing Methods

• Starvation: removing the fuel source
• Cooling: lowering the temperature below the ignition temperature
• Smothering: cutting off the oxygen supply

Types of Fires

• Different types of fires and their specific extinguishers are important to understand to effectively combat fires
• Understanding combustion and its various forms is essential in different applications, such as fire safety, chemical reactions, and energy production### Understanding Fire and Combustion
• Fire is classified into different types: Class A fires refer to burning paper or cloth; Class B fires involve flammable or inflammable liquids like petrol and oil; Class C fires occur due to flammable gases; Class D fires arise from reactive metals like sodium, potassium, and magnesium; Class E refers to electrical fires; Class F fires pertain to cooking oils and gases.
• Each type of fire requires a specific method of extinguishing. For example, it's advisable not to use water on petrol, oil, or electrical fires.
• Water is the most accessible substance used to douse fires. However, it cannot be used on all types of fires. For instance, when used on petrol or oil fires, it will cause the burning liquid to overflow and spread, intensifying the fire.
• Using water on electrical fires can lead to electrocution, hence it's not recommended. Similarly, using water on fires caused by reactive metals can lead to explosions as these metals react violently with water.
• In the event of a large-scale fire due to reactive metals, the usage of special dry powders or sand is recommended. The powders can include sodium bicarbonate (baking soda) or specific commercially designed powders for chemical fires.
• Carbon dioxide is often used as fire extinguisher material due to its capability to displace oxygen around the fire, stopping the combustion process. However, the use of carbon dioxide is limited to Class B fires and some electrical fires, but never on metal fires.
• The phenomenon of a candle flame always moving upward is due to the process called convection currents.
• The mechanism involved in burning includes the generation of heat energy, followed by the restructuring of different molecules and chemical substances in the combustion process. This process emits light and heat.
• Incomplete combustion occurs because of a lack of oxygen. This leads to the emission of particles that are still burning and glowing, giving the flame its characteristic colors.### Hydrocarbons and Combustion
• Incomplete combustion of hydrocarbons produces a yellow flame due to the presence of unburned carbon particles, which are not fully oxidized to CO2.
• Complete combustion of hydrocarbons produces a blue flame, indicating complete oxidation to CO2.
• Incomplete combustion occurs when there is a lack of oxygen, resulting in the production of carbon monoxide (CO) instead of CO2.

Characteristics of a Good Fuel

• A good fuel should have a high calorific value, meaning it releases a large amount of energy per unit mass when burned.
• A good fuel should be easily available, economically viable, and environmentally friendly.
• The ideal fuel should have all these characteristics, but it is impossible to find a fuel that meets all these criteria.

Types of Fuels

• Kerosene has a calorific value of 40,000 kJ/kg.
• Petrol has a calorific value of 45,000 kJ/kg.
• Diesel has a calorific value of 50,000 kJ/kg.
• Hydrogen has the highest calorific value of all fuels, at 150,000 kJ/kg.

Carbon Monoxide and Hemoglobin

• Carbon monoxide (CO) is a poisonous gas that can bind to hemoglobin in the blood, reducing its ability to carry oxygen.
• Hemoglobin has a higher affinity for CO than oxygen, making it difficult to remove CO from the blood.
• This can lead to hypoxia, a condition where the body does not receive enough oxygen.

Environmental Impact

• Burning fuels releases pollutants such as nitrogen oxides, sulfur oxides, and carbon dioxide, which contribute to environmental problems like acid rain and the greenhouse effect.

Review of Key Concepts

• Review the complete combustion of hydrocarbons, the characteristics of a good fuel, and the environmental impact of burning fuels.

Combustion Process

• Combustion is a chemical reaction between a combustible substance and oxygen, producing heat and light energy, along with various products.
• Combustion can occur in different forms, such as flames or just glowing (heat energy).

Types of Combustion

• Rapid combustion: occurs quickly, often with the help of an external heat source.
• Spontaneous combustion: occurs without an external ignition source, when reactive substances come into contact with oxygen.
• Explosive combustion: occurs rapidly, releasing heat, light, and sound energy.

Fire Triangle

• The fire triangle consists of three essential elements: fuel, heat, and oxygen.
• Removing any one of these elements can stop the fire.

Fire Extinguishing Methods

• Starvation: removing the fuel source to stop the fire.
• Cooling: lowering the temperature below the ignition temperature to extinguish the fire.
• Smothering: cutting off the oxygen supply to stop the fire.

Types of Fires

• Class A fires: involve burning paper or cloth.
• Class B fires: involve flammable or inflammable liquids like petrol and oil.
• Class C fires: occur due to flammable gases.
• Class D fires: arise from reactive metals like sodium, potassium, and magnesium.
• Class E fires: refer to electrical fires.
• Class F fires: pertain to cooking oils and gases.

Fire Extinguishing

• Each type of fire requires a specific method of extinguishing.
• Water is not suitable for all types of fires, such as petrol, oil, or electrical fires.
• Special dry powders or sand are recommended for fires involving reactive metals.
• Carbon dioxide is used as a fire extinguisher for Class B fires and some electrical fires.

Combustion Process

• The mechanism of burning involves the generation of heat energy, followed by the restructuring of molecules and chemical substances.
• Incomplete combustion occurs due to a lack of oxygen, leading to the emission of particles that are still burning and glowing.

Hydrocarbons and Combustion

• Incomplete combustion of hydrocarbons produces a yellow flame due to unburned carbon particles.
• Complete combustion of hydrocarbons produces a blue flame, indicating complete oxidation to CO2.

Characteristics of a Good Fuel

• A good fuel should have a high calorific value, releasing a large amount of energy per unit mass when burned.
• A good fuel should be easily available, economically viable, and environmentally friendly.

Learn about the combustion process, its types, and the chemical reactions involved. Understand the differences between rapid and spontaneous combustion.