Match the given columns: Column A Column B Column C 1. Physical changes (i) Reacts with sulphur (a) Rust 2. Copper sulphate (ii) Irreversible (b) Chemical change 3. Iron (iii) No new substance is formed (c) Basic in nature 4. Carbon (iv) Turns red litmus paper blue (d) Generally reversible 5. Spoilage of food (v) Reacts with zinc (e) Zinc sulphate is formed 6. Magnesium hydroxide (vi) Oxygen and water (f) Endothermic reaction

In physical changes only the physical properties of the substances change. Hence, no new substance is formed and these are generally reversible changes. As zinc is more reactive than copper, it displaces copper from copper sulphate solution and forms zinc sulphate solution. Blue colour of copper sulphate solution changes into colourless solution. When an iron object is exposed to oxygen and water, it results in the formation of a brown flaky layer on its surface which is known as rust. The process is known as rusting. Carbon is made to react with the sulphur by absorbing heat energy to form carbon disulphide. As this reaction proceeds with the absorption of heat energy, it is known as endothermic reaction. Spoilage of food is an irreversible chemical change. Magnesium hydroxide is a basic solution. Hence, it turns red litmus to blue. Column A Column B Column C 1. Physical changes (iii) No new substance is formed (d) Generally reversible 2. Copper sulphate (v) Reacts with zinc (e) Zinc sulphate is formed 3. Iron (vi) Oxygen and water (a) Rust 4. Carbon (i) Reacts with sulphur (f) Endothermic reaction 5. Spoilage of food (ii) Irreversible (b) Chemical change 6. Magnesium hydroxide (iv) Turns red litmus paper blue (c) Basic in nature

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Start Up Science 7>Chapter 6 - How Things React With One Another>EXERCISES FOR FORMATIVE AND SUMMATIVE ASSESSMENT>Q B

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7th CBSE

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What is crystallization?

Important Questions on How Things React With One Another

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Start Up Science 7>Chapter 6 - How Things React With One Another>EXERCISES FOR FORMATIVE AND SUMMATIVE ASSESSMENT>Q C

Match the given columns:

	Column A		Column B		Column C
1.	Physical changes	(i)	Reacts with sulphur	(a)	Rust
2.	Copper sulphate	(ii)	Irreversible	(b)	Chemical change
3.	Iron	(iii)	No new substance is formed	(c)	Basic in nature
4.	Carbon	(iv)	Turns red litmus paper blue	(d)	Generally reversible
5.	Spoilage of food	(v)	Reacts with zinc	(e)	Zinc sulphate is formed
6.	Magnesium hydroxide	(vi)	Oxygen and water	(f)	Endothermic reaction