Which of the following is the chemical reaction is brought about by heat. rusting of iron . boiling of water .combustion of methane
Answers
Explanation:
Those changes in which new substances are formed, are called chemical changes. The properties of new substances formed in chemical changes are entirely different from those of the original substances.
During chemical change, a substance undergoes a change in its chemical composition (or change in chemical properties). Chemical changes are also called chemical reactions.
Characteristics of a chemical change :
(1) One or more new substances are formed in a chemical change.
(2) A chemical change is a permanent change. A chemical change usually cannot be reversed.
(3) A lot of energy (in the form of heat, light, etc.) is either absorbed or given out in a chemical change.
(4) Sound may be produced in a chemical change.
(5) A change in smell may take place or a new smell may be given off in a chemical change.
(6) A permanent change in colour may take place in a chemical change.
(7) A gas may be formed in a chemical change.
If we burn a piece of paper with a lighted match stick, then entirely new substances such as carbon dioxide, water vapour, smoke and ash are produced. So, the burning of paper is a chemical change. Heat and light are also given out during the burning of paper. The burning of paper is a permanent change which cannot be reversed. We cannot combine the products of burning of paper to form the original paper again. Burning is always accompanied by the production of heat and light.
Examples of chemical changes :
Souring of milk
Formation of curd from milk
Cooking of food (like rice and chapatis)
Spoilage of food
Change in colour of cut apple (cut brinjal or cut potato) on keeping in air
Photosynthesis
Digestion of food
Neutralisation reaction
Explosion of a firework (or cracker)
Burning of magnesium ribbon
Burning of fuels (like burning of wood, coal, kerosene, LPG and biogas)
Burning of dry leaves
Burning of candle wax
Burning of incense stick
Rusting of iron
Ripening of fruits
Reaction between vinegar and baking soda
Passing carbon dioxide gas through lime water (which produces calcium carbonate precipitate)
Reaction between copper sulphate solution and iron
Formation of manure (or compost) from leaves
Formation of biogas from animal wastes (like cow-dung).
When food gets spoiled, it produces a foul smell. This shows that new substances have been formed in the spoiled food which have foul smell. The spoilage of food is a chemical change.
Answer:
rusting of iron
Explanation:
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