Page 146 - ICSE Chemistry 8

3. What are photochemical reac ons? Explain with examples.
4. What happens when a pinch of manganese (IV) oxide is added to hydrogen peroxide in a test tube?

5. Write the func ons of the enzymes pepsin and maltase.
6. What is thermal decomposi on? Explain with the help of examples.

7. What causes acidity and indiges on? How can this condi on be treated?
8. What happens when an ant or a bee s ngs? How can the eff ect of an ant or a bee s ng be neutralised?

9. What is the eff ect of excessive use of fer lisers on soil? How is the soil treated if it is too acidic?

10. Why are the wastes released from the factory treated before being released to the water bodies?
11. What is reac vity or ac vity series of metals? Represent the series.

12. What are alkalis? Explain with examples.

AT LENGTH

A. Diff eren ate between the following.
1. Exothermic reac ons and endothermic reac ons

2. Catalyst and enzyme
3. Posi ve catalyst and nega ve catalyst

4. Combina on reac on and decomposi on reac on
5. Displacement reac on and double displacement reac on

6. Oxida on and reduc on
7. Oxidising agent and reducing agent

8. Calcina on and roas ng
9. Acidic oxides and basic oxides
10. Amphoteric oxides and neutral oxides

B. Read the following ac vity performed to demonstrate the neutralisa on reac on. Iden fy the
incorrect parts.

To show neutralisa on reac on
• Take about 100 mL calcium hydroxide in a conical fl ask.
• Add 9–10 drops of phenolphthalein solu on to it. The solu on turns green.

• Now add dilute sulphuric acid dropwise with the help of a test tube. Shake well each me you add
a drop.
What do you observe a er some me?
The solu on becomes pink.

• Now add a drop of calcium hydroxide solu on.
The solu on becomes colourless.
• Again add a drop of dilute sulphuric acid.

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