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Activity 4.2 (Caution : Be careful while handling Rightly so. In our body burning candle). food is broken down by Fix a lighted candle on a table. Put reaction with oxygen and heat is produced. We a glass chimney over the candle and learnt that in Class VII. rest it on a few wooden blocks in such a way that air can enter the Activity 4.1 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 (a) (b) (c) combustible, otherwise mark it Fig. 4.2: Experiment to show that air is non-combustible (Table 4.1). essential for burning Table 4.1 : Combustible and Non- chimney [Fig. 4.2(a)]. Observe what combustible Substances happens to the flame. Now remove Material Combustible Non- the blocks and let the chimney rest combustible on the table [Fig. 4.2(b)]. Again observe the flame. Finally, put a Wood glass plate over the chimney [Fig. Paper 4.2(c)]. Watch the flame again. What happens in the three cases? Does Iron nails the flame flicker off? Does it flicker Kerosene oil and give smoke? Does it burn Stone piece unaffected? Can you infer anything at all about the role played by air in Straw the process of burning? Charcoal We find that for combustion, air is Matchsticks necessary. The candle burns freely in Glass case (a) when air can enter the chimney from below. In case (b), when Can you name some more air does not enter the chimney from substances which are combustible? You below, the flame flickers and produces can add those to Table 4.1. smoke. In case (c), the flame finally Let us investigate conditions under goes off because the air is not which combustion takes place. available. COMBUSTION AFLAME 41 2024-25