i. Cutting a log of wood into pieces is a physical change.
ii. Condensation is a physical change.
iii. When carbon dioxide is passed through lime water, it turns milky due to the formation of Calcium Carbonate.
iv. Two methods by which rusting of iron can be prevented are painting or greasing and galvanisation.
v. Changes in which only physical properties of a substance change are called physical changes.
vi. A medicine is the end product of a chain of chemical reactions.
i. Formation of manure from leaves is a physical change. False
ii. Iron pipes coated with zinc do not get rusted easily. True
iii. Iron and rust are the same substances. False
iv. The chemical name of baking soda is Sodium hydrogencarbonate. True
v. Changes in which new substances are formed are called chemical changes. True
Ans. It is a physical change.
Ans. Rusting of iron is a chemical change.
Ans. It does not rust.
Ans. Formation of manure is a chemical change.
Ans. Chemical change is a permanent change.
Ans. A change in which one or more new substances are formed is called a chemical change.
Ans. For rusting, the presence of both oxygen and water (or water vapour) is essential.
Ans. The process of depositing a layer of metal like zinc or chromium on iron is called galvanisation.
Ans. Stainless steel is made by mixing iron with carbon and metals like chromium, nickel and manganese.
Ans. Formation of manure from leaves is a chemical change because manure formed has a different composition from leaves.
Ans. Souring of milk is a chemical change because it results in formation of new substance.
Ans. If a piece of iron is left in the open for some time, it acquires a film of brownish substance. This substance is called rust.
Ans. Crystals of copper sulphate pentahydrate are blue in colour. So, it is commonly known as blue vitriol.
Ans. Two methods by which rusting of iron can be prevented are by painting or greasing and by galvanizing.
Ans. Vinegar (Acetic acid) + Baking soda (Sodium hydrogencarbonate) → Carbon dioxide + other substances
Ans. Crystallization is considered as a better technique for obtaining sugar from sugar solution.
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