Question

9. What is the colour of phenolphthalein acidic and basic media?
10. Explain why factory waste should be neutralized before disposing it into the water bodies?
11. Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. What is its nature?
12. Give examples of some acid and bases.
13. How does rain becomes acidic?
14. Name the source from which litmus solution is obtained. What is the use of this solution?
15.Explain the process of neutralization with example. Red litmus paper is dipped in a solution; it remains red, what is the nature of the solution?
16.What are chemical reactions? Differentiate between combination and decomposition reaction.
17. What is displacement reaction? Give example.
18. Differentiate between physical and chemical change. Give example.
19. (a)Explain two methods by which rusting can be prevented .(b) Burning of a candle may be considered as showing physical and chemical changes occurring simultaneously. Explain.
20.Explain an activity to show that chemical change is irreversible and permanent.

Answer 1

13.when rain comes on earth ,it trapped and react with oxides of sulpher and nitrogen .thus rain turns into acidic rain

Answer 2

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9. In a Acidic Solutions it turns colorless and In Basic Media it turns to Red.

10. Factory Wastes are neutailized because it often contains acids which kills Water Bodies. So before sending it to water Bodies it is neutailized by adding Basic substances.

11. The nature of the solution is Basic.

12. The examples of Acids and Bases are:-
Acids- Oxalic Acid, Butyric Acid, Carbonic
Acid.
Bases- Sodium Hydroxide, Calcium
Hydroxide, Magnesium
Hydroxide.

13. Acid rain is caused by Chemical Recations that begins with the compounds like Sulphur Dioxide and Nitrogen Oxide are released into air. These substances can raise very high into the atmosphere where they mix and react with air, oxygen and other chemicals to form more acidic pollutants, known as Acid Rain.

14. Litmus Paper is obtained from Litmus. It is used to differentiate between Acids and Bases.

15. Neutailization is a process in which Acid and Base are mixed together to form Salt. This is called Neutralization.
A wasp sting, on the other hand, is mildly basic, so a household remedy for this will be vinegar, also known as acetic acid.
If Red Litmus Paper is dipped in a solution and remains red, The nature of the solution is red.

18. •Physical Changes- Physical changes occur when objects or substances undergo a change that does not change their chemical composition. 
Eg- Melting of Ice
•Chemical Changes- Chemical changes occur when a substance combines with another to form a new substance.
Eg- Burning of Paper

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