UU 1. A flame produced with the evolution of heat and very little light 2. A substance that burns in air or oxygen to produce heat and light 3. The amount of heat energy produced on complete combustion of 1 kg of a fuel 4. When a substance burns smoothly at a moderate rate. 5. Zone of complete combustion 6. The visible gaseous part of a fire
Answers
Answer:
Introduction
People generally use wood, cowdung cakes, crop residues, kerosene oil, coke or LPG gas to cook food. For ruining vehicles, we use petrol or diesel oil. In factories, we use coal or fuel oil or natural gas.
The materials, such as wood, coke, LPG (liquid petroleum gas), petrol, diesel, natural gas have one property [n common, i.e., they produce heat on burning which is then put into different uses. Furthermore, some materials on burning produce flame and some do not. For example, a candle or coal gas on burning produces a flame, but not the coal or charcoal. So, let us study the chemical process of burning and the types of flame produced during this process.
Combustion
Some substances, like magnesium catches fire and burns with a dazzling white flame when heated in air. Similarly, when a piece of per is brought near a candle flame, it burns, producing heat and light. The charcoal and coal bums in air producing carbon dioxide, heat and light.
Air or oxygen which helps in burning is called supporter of combustion and the chemical reaction which takes place with the release of heat and light energy is called combustion.
A chemical process in which a substance reacts with oxygen to give off heat is called combustion.
The substances which undergo combustion are known as combustible substances. It may also be called a fuel.
Sometimes, heat is accompanied by light, either as a flame or as a glow, during combustion.
Fuel may be solid, liquid or gas. A combustion reaction maybe written as-
(a) Charcoal burns in air to give carbon dioxide and heat.
C + O2 → CO2 + Heat
(b) Methane bums in air forming carbon dioxide, water and heat.
CH4 + 2O2 → CO2 + 2H2O + Heat
Test Yourself
1. Which of the following is combustible?
(a) Iron nail
(b) Glass
(c) Stone pieces
(d) Paper
2. Combustion is a
(a) physical process
(b) chemica
(c) Both (a) & (b)
(d) None
Conditions required for combustion
Now, let us study the conditions under which combustion takes place with the help of following activities.