Show that fuel/substance should be heated to its ignition temperature to make it burn

Objective

Show that fuel/substance should be heated to its ignition temperature to make it burn.

 

Theory

Combustion

Combustion is a chemical reaction that often involves the presence of oxygen and produces heat and light in the form of flame. This defines the nature of the chemical reaction. When more energy is released into the surrounding medium, the rate at which the reactants combine increases significantly. Consequently, the temperature of the reactants is increased, further accelerating the process.

Types of Combustion

  • Complete Combustion
  • Incomplete Combustion
  • Rapid Combustion
  • Spontaneous Combustion
  • Explosion

Complete Combustion

Complete combustion occurs when there is an ample supply of oxygen, leading to the efficient and thorough burning of the fuel. In this process, the fuel is oxidized completely to produce carbon dioxide and water as byproducts. The general equation represents the reaction: fuel + oxygen → carbon dioxide + water. 

Incomplete Combustion

Incomplete combustion occurs when insufficient oxygen is available during the burning process. As a result, the fuel does not fully oxidize, producing incomplete byproducts such as carbon monoxide and unburned carbon particles. Incomplete combustion is often characterized by a less intense flame and the release of sooty smoke. This type of combustion is less energy-efficient and can pose environmental and health hazards due to the emission of harmful substances. 

Rapid Combustion

Rapid combustion, also known as rapid burning or rapid oxidation, occurs at an accelerated rate, releasing a significant amount of energy in a short period. This phenomenon is characterized by a sudden and intense reaction between a fuel and an oxidizing agent, typically oxygen, in the air. Rapid combustion is swift, unlike slow or controlled combustion, which occurs steadily and is commonly seen in processes like respiration or slow-burning fires. It often produces heat and light in an explosive manner. 

Spontaneous Combustion

When a hydrocarbon or other chemical substance spontaneously ignites into flame without apparent cause, the process is known as spontaneous combustion. This contrasts with ordinary combustion, where the hydrocarbon is purposefully heated to the point of ignition before being allowed to burn. Spontaneous combustion is a fascinating but potentially hazardous phenomenon that occurs when a substance ignites without an external heat source. This spontaneous ignition typically happens when certain materials, often organic, undergo a chemical reaction that generates heat as a byproduct. One of the most common examples is the spontaneous combustion of oily rags or hay. 

Explosion 

Explosion is the term used to describe combustion followed by the sudden generation of heat, sound, and massive amounts of gas. A blinding flash of light accompanied the sudden burst of sound. Bombs and firecrackers are examples of explosives. Some substances do not exhibit a flame during combustion. .

Ignition Temperature

The ignition temperature, also known as the kindling point, is crucial for various substances when considering combustion. It refers to the minimum temperature at which a material can ignite and sustain combustion in the presence of an external ignition source. The ignition temperature is vital for fire safety assessments and preventing unintentional combustion events. A combustible substance cannot catch fire if it is lower than its ignition temperature. 

 

Learning Outcomes

  • Students can understand what is combustion.
  • Students can understand the types of combustion and its examples.
  • Students understand what is  ignition temperature.