How can you say that magnesium and charcoal both are Combustible materials?
Answers
Answer:
Chemical Process of Burning
We use different kinds of fuel for various purposes at home, in industry and for running automobiles.Some of the fuels are like cowdung, wood, coal, charcoal, petrol, diesel, compressed natural gas (CNG), etc.
You are familiar with the burning of a candle. Note the difference between the burning of a candle and the burning of a fuel like coal. May be you were able to guess right: candle burns with a flame whereas coal does not. Similarly, you will find many other materials burning without a flame. Let us study the chemical process of burning and the types of flame produced during this process.
What is Combustion?
Recall the activity of burning of magnesium ribbon. We learnt that magnesium burns to form magnesium oxide and produces heat and light .
We can perform a similar activity with a piece of charcoal. Hold the piece with a pair of tongs and bring it near the flame of a candle or a Bunsen burner. We find that charcoal burns in air. We know that coal, too, burns in air producing carbon dioxide, heat and light.
A chemical process in which a substance reacts with oxygen to give off heat is called combustion. The substance that undergoes combustion is said to be combustible. It is also called a fuel. The fuel may be solid, liquid or gas. Sometimes, light is also given off during combustion, either as a flame or as a glow.
In the reactions mentioned above magnesium and charcoal are combustible substances.
Let us consider an example. Collect some materials like straw, matchsticks, kerosene oil, paper, iron nails, stone pieces, glass, etc. Under the supervision of your teacher try to burn each of these materials one by one. If combustion takes place mark the material combustible, otherwise mark it as non-combustible in a table. Name some more substances which are combustible and add those to the Table.
Let us investigate conditions under which combustion takes place.
Examples
Caution : Be careful while handling burning candle.
Fix a lighted candle on a table. Put a glass chimney over the candle and rest it on a few wooden blocks in such a way that air can enter the chimney. Observe what happens to the flame. Now remove the blocks and let the chimney rest on the table. Again observe the flame. Finally, put a glass plate over the chimney . Watch the flame again. We find that for combustion, air is necessary. The candle burns freely in case (a) when air can enter the chimney from below. In case (b), when air does not enter the chimney from below, the flame flickers and produces smoke. In case (c), the flame finally goes off because the air is not available.
In the sun, heat and light are produced by nuclear reactions.
Place a piece of burning wood or charcoal on an iron plate or Tawa. Cover it with a glass jar or a tumbler, or a transparent plastic jar. Observe what happens. Charcoal stop burning after sometime. You might have heard that when the clothes of a person catch fire, the person is covered with a blanket to extinguish fire. Guess the reason for it.
Recall some of your experiences burning a piece of paper. You have to use paper or kerosene oil to start fire in wood or coal.During extreme heat of summer, at some places dry grasses catch fire. From grasses, it spreads to trees, and very soon the whole forest is on fire. It is very difficult to control such fires.This is called Forest Fire.
The lowest temperature at which a substance catches fire is called its ignition temperature.
We find that a combustible substance cannot catch fire or burn as long as its temperature is lower than its ignition temperature. Have you ever seen cooking oil catching fire when a frying pan is kept for long on a burning stove? Kerosene oil and wood do not catch fire on their own at room temperature. But, if kerosene oil is heated a little, it will catches fire. But if wood is heated a little, it would still not catch fire. Ignition temperature of kerosene oil is lower than that of wood. We need to take special care in storing kerosene oil. The following activity shows that it is essential for a substance to reach ignition temperature to burn.
Explanation:
Answer:
The burning of magnesium in air to produce heat and light is a combustion process. Magnesium is a combustible substance. When charcoal burns,then the carbon of charcoal combines with the oxygen of air to form carbon dioxide. A lot of heat is produced in the combustion reaction but only a little light is produced.