Combustion of a substance in oxygen or air is so common that it becomes almost a habit to use the word "combustion" as if it referred to this kind of reaction alone. In real sense, it may be applied to any chemical reaction accompanied by light and heat in which one or more of the reactants are gaseous.
Many common substances burn in air. Substances such as coal, wood, kerosene, petrol, etc., burn in air. Any substance that burns is called a combustible material. The air or oxygen that supports the combustion is called a supporter of combustion. This is because we live in an atmosphere of air that contains oxygen, which is a very reactive gas.
The gas surrounds any burning material. Oxygen is regarded as a supporter of combustion. However, it can sometimes combine chemically with the burning substance to produce a new substance, as we shall see later.
Combustion of a substance involves its reaction with oxygen and the release of energy. These reactions are exothermic and often produce a flame. An exothermic reaction is the one that is accompanied by release of heat to the surrounding environment. Combustion in which a flame is produced is described as burning. During burning energy is given out in the form of heat, light and sound.
Sulphur
This is a yellow powder. When burnt in air, it gives misty fumes of Sulphur dioxide gas.
Copper
When a piece of copper foil in a pair of tongs is held in a Bunsen flame, it becomes red-hot. On cooling, a black layer of some substance is observed. This black substance is copper oxide. The reaction occurs thus:
Magnesium
When one end of a piece of magnesium ribbon in tongs is placed in a Bunsen flame, it burns with a dazzling flame leaving a white ash. This white ash is magnesium oxide.
Hydrocarbons
Candle wax is a hydrocarbon. When it burns in air, the carbon and hydrogen of the wax react with the oxygen of the air to give carbon dioxide and water vapor respectively.
These are substances containing carbon and hydrogen only. The burning of these organic substances produces carbon dioxide and water vapor as the main products. If oxygen supply is low, combustion is incomplete and carbon monoxide may be formed.
Coal
Coal is a solid fuel that will burn in air to give the following products:
Combustion of a substance involves its reaction with oxygen and the release of energy. These reactions are exothermic and often produce a flame. An exothermic reaction is the one that is accompanied by release of heat to the surrounding environment. Combustion in which a flame is produced is described as burning. During burning energy is given out in the form of heat, light and sound.
The Combustion of Different Substances in Air and Analyze the Products
Many different substances burn in air to produce different products. Here are examples of combustion of some common substances:Sulphur
This is a yellow powder. When burnt in air, it gives misty fumes of Sulphur dioxide gas.
Copper
When a piece of copper foil in a pair of tongs is held in a Bunsen flame, it becomes red-hot. On cooling, a black layer of some substance is observed. This black substance is copper oxide. The reaction occurs thus:
Magnesium
When one end of a piece of magnesium ribbon in tongs is placed in a Bunsen flame, it burns with a dazzling flame leaving a white ash. This white ash is magnesium oxide.
Hydrocarbons
Candle wax is a hydrocarbon. When it burns in air, the carbon and hydrogen of the wax react with the oxygen of the air to give carbon dioxide and water vapor respectively.
These are substances containing carbon and hydrogen only. The burning of these organic substances produces carbon dioxide and water vapor as the main products. If oxygen supply is low, combustion is incomplete and carbon monoxide may be formed.
Coal
Coal is a solid fuel that will burn in air to give the following products:
The Application of Combustion in Real Life
1. The combustion of a natural gas is an important source of energy for homes and industry. Natural gas is mainly methane. Its complete combustion produces carbon dioxide and water vapour. Substances like methane, which undergo combustion readily and give out large amount of energy, are known as fuels.2. There are some reactions where fuels and other substances burn to produce a flame. These are combustion reactions. There are also other combustion reactions (exothermic) where no flame is evident. The most important of these is the crucial biochemical reaction that releases energy in our body cells called cellular respiration.
Our bodies need energy to make possible the reactions that take place in our cells. These reactions allow us to carry out our everyday activities. We need energy to stay alive. We get this energy from food. During digestion, food is broken down into simpler substances.
For example, the carbohydrates in rice, potatoes and bread are broken down to form glucose. The combustion of glucose with oxygen in the cells of our body provides energy.
The reaction is exothermic and is known as cellular respiration.
3. We combust fuels to heat homes and keep ourselves warm, cook our food, and even burn wastes.
4. Combustion of fuels in automobile engines produces power (energy).
The reaction is exothermic and is known as cellular respiration.
3. We combust fuels to heat homes and keep ourselves warm, cook our food, and even burn wastes.
4. Combustion of fuels in automobile engines produces power (energy).
This energy is supplied to different parts of motor vehicles to make them move from one point to another or carry out some crucial activities such as grinding, pumping, hauling etc. The operation of such machines could be impossible without combustion of fuel that produces energy to make them work.
5. Combustion of fuel in different burners produces heat and light used for different purposes in a chemistry laboratory.
6. Extraction of metals: Moderately reactive metals such as zinc, iron and lead are roasted in a special furnace (kiln) to form oxides. The resulting oxides are then reduced with carbon to get the pure metal. This process of extracting a metal from its ore by heating is called smelting.
7. In metallurgical industry, combustion is used during welding. Welding is the process of joining metals by melting the parts and then using a filler to form a joint. It can be done using different energy sources, including a gas flame.
5. Combustion of fuel in different burners produces heat and light used for different purposes in a chemistry laboratory.
6. Extraction of metals: Moderately reactive metals such as zinc, iron and lead are roasted in a special furnace (kiln) to form oxides. The resulting oxides are then reduced with carbon to get the pure metal. This process of extracting a metal from its ore by heating is called smelting.
7. In metallurgical industry, combustion is used during welding. Welding is the process of joining metals by melting the parts and then using a filler to form a joint. It can be done using different energy sources, including a gas flame.
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