Acids, Bases and Salts — Science STD 7 — Question

What is neutralisation? Give examples of neutralisation in daily life.

Write how the following seeds are dispersed.

1. Seeds with wings.
2. Small and light seeds.
3. Seeds with spines/ hooks.

Make a sketch showing groundwater and water table. Label it.

Explain how groundwater is recharged?

Neha went to the market with her mother to buy a silk saree for her grandmother. The shopkeeper was showing sarees of different varieties of silk but her mother wanted to take only a pure silk saree and not an artificial one. Neha was confused that how to distinguish between a pure silk and an artificial silk saree. But her mother helped her in selecting a pure silk saree for her grandmother and she was quite elated about that.
Now, answer the following Questions:

1. How her mother distinguished between pure silk saree and an artificial silk saree?
2. Is the pure silk saree more costly than an artificial one?
3. What values are shown by Neha’s mother?

Nitrogen is an essential nutrient for plant growth. But farmers who cultivate pulse crops like green gram, bengal gram, black gram, etc. do not apply nitrogenous fertilizers during cultivation. Why?

What are decomposers? Name any two of them. What do they do in the forest?

Explain the sea breeze and land breeze.

Visit a forest with your parents by taking permission from the respective authority (forest officials).
(i) Make a list of the things you see in the forest.
(ii) Try to recognise various types of trees and different layers formed by them.

Fill in the cross word given as Figure 5.2 with the help of the clues provided. Across:

2. The solution which does not change the colour of either red or blue litmus.
3. Phenolphthalein gives pink colour in this type of solution.
4. Colour of blue litmus in lemon juice.

Down:

1. It is used to test whether a substance is acidic or basic.

3. It is a natural indicator and gives pink colour in basic solution.

5. Nature of ant’s sting.

6. It is responsible for increase in temperature during a neutralisation reaction.