Q10 of 16 Page 65

Explain why rusting of iron objects is faster in coastal areas than in deserts.

Both air and moisture are necessary conditions for rusting to take place. In coastal areas, the amount of moisture present in air is higher than that in desert areas. So, the process of rusting is faster in coastal areas than in deserts.


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Describe how crystals of copper sulphate are prepared.

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Explain how painting of an iron gate prevents it from rusting.

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The gas we use in the kitchen is called liquified petroleum gas (LPG). In the cylinder it exists as a liquid. When it comes out from the cylinder it becomes a gas (Change - A) then it burns (Change - B). The following statements pertain to these changes. Choose the correct one.

(i) Process - A is a chemical change.


(ii) Process -B is a chemical change.


(iii)Both processes A and B are chemical changes .


(iv) None of these processes is a chemical change.

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Anaerobic bacteria digest animal waste and produce biogas (Change - A). The biogas is then burnt as fuel (Change - B). The following statements pertain to these changes. Choose the correct one.

(i) Process - A is a chemical change.


(ii) Process -B is a chemical change.


(iii)Both processes A and B are chemical changes .


(iv) None of these processes is a chemical change.