Chemical Changes and Reactions Goyal Brothers ICSE Class-9 Part-1

Chemical Changes and Reactions Goyal Brothers ICSE Class-9 Part-1 Chapter-2. We Provide Solutions of all type exercise questions such as reactions, definition fill in the blanks give reason etc.. Visit official Website CISCE  for detail information about ICSE Board Class-9.

ICSE Class-9 Ch-2 Chemical Changes and Reactions Part-1 Goyal Brothers

Ch-2 Chemical Changes and Reactions Part-1

Goyal Brother Prakashan ICSE Class-9 Chemistry Solutions

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Questions 1.

(a) Define chemical change –A chemical change is a change of materials into another, new materials with different properties and one or more than one new substances are formed. It results when a substance combines with another to form a new substance (synthesis or either decomposes to form more substances)

(b) Give four examples of a chemical change.–Examples of chemical changes are burning, cooking, rusting, and rotting.

Questions 2. State Four characteristics of a chemical change.

Answer : The  conditions of chemical change: color change, formation of a precipitate, formation of a gas, odor change, temperature change

Questions 3. What do you understand by the following terms? Give examples:

(a) Endothermic chemical change.--Endothermic reactions are chemical reactions in which the reactants absorb heat energy from the surroundings to form products. These reactions lower the temperature of their surrounding area, thereby creating a cooling effect.

(b) Exothermic chemical change.–An exothermic reaction is a chemical reaction in which less energy is needed to break bonds in the reactants than is released when new bonds form in the products. During an exothermic reaction, energy is constantly given off, often in the form of heat. All combustion reactions are exothermic reactions

Questions 4. How can you say these are chemical changes? Give one reason for your answer.

(a) Burning of candle–When a candle burns, the oxygen in the air reacts, formation of carbon dioxide takes place.

(b) Milk sours in hot and humid weather—Due to hot and humid weather lactose sugar present in the milk is converted into lactic acid which is a new substance formed

(c) Decomposition of water into hydrogen and Oxygen.-– hydrogen and oxygen gases are produced from liquid water. The electrolysis of water causes a chemical change in which water molecules are split to form hydrogen and oxygen—two substances that are chemically different from water.

(d) Rusting of iron–When the iron is exposed to air and moisture, rust formation takes place. Rust is nothing but iron oxide; a new substance formed out of the reaction. The colour of the surface of the iron also changes. Hence, rusting of iron is a chemical change

(e) A frog breathes heavily– it is a chemical process as it utilizes this oxygen to break food to release energy

Questions 5. A person eats a chocolate and then digests it. In doing so there takes place a chemical change. identify the change and give reason for your answer.

Answer : A person eats a chocolate and then digests it, so there takes a chemical change because in the stomach digestion is held, the stomach adds special chemicals to digest it which when done is in-reversible. So, it is a chemical change because chemical changes are ir-reversible.

Questions 6. We mix iron filings with sulphur and grind it, and we heat the mixture, a chemical change takes place. Using the above example explain the chemical change.

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