Secondary School (English Medium) (5 to 8) इयत्ता ७ - CBSE Question Bank Solutions for Science

State whether the following statement is True or False. In case a statement is false, write the correct statement.

Used water is wastewater

State whether the following statement is True or False. In case a statement is false, write the correct statement.

Wastewater could be reused

State whether the following statement is True or False. In case a statement is false, write the correct statement.

Where underground sewerage systems and refuse disposal systems are not available, the high cost on-site sanitation system can be adopted

Given below is a jumbled sequence of the processes involved in a wastewater treatment plant. Arrange them in their correct sequence.

1. Sludge is scraped out and skimmer removes the floating grease. 
2. Water is made to settle in a large tank with a slope in the middle.
3. Large objects like plastic bags are removed by passing wastewater through bar screens.
4. Sand, grit and pebbles are made to settle by decreasing the speed of incoming wastewater.
5. Wastewater enters a grit and sand removal tank.

Three statements are provided here which define the terms –

1. sludge
2. sewage and
3. wastewater.

Pick out the correct definition for each of these terms.

1. The settled solids are removed in wastewater treatment with a scraper.
2. Water from the kitchen is used for washing dishes.
3. Wastewater is released from homes, industries, hospitals and other public buildings.

Describe various steps of cleaning wastewater in a wastewater treatment plant.

Collect data from your friends, neighbours and classmates to know more about “milk teeth".

Tabulate your data. One way of doing it is given below:

Find out from at least twenty children and find the average age at which children lose the milk teeth. You may take help of your friends.

Describe two changes that are harmful. Explain why you consider them harmful. How can you prevent them?

Visit a laughing gallery in some science centre, or a science park or a village mela. You will find some large mirrors there. You can see your distorted and funny images in these mirrors. Try to find out the kind of mirrors used there.

What is sludge?

How would you test the presence of starch in leaves?

Give a brief description of the process of synthesis of food in green plants.

Show with the help of a sketch that the plants are the ultimate source of food.

In photosynthesis, solar energy is absorbed by the pigment called ______.

During photosynthesis plants take in ______ and release ______ gas.

Name the following:

A plant that has both autotrophic and heterotrophic mode of nutrition.

Name the following: 

The pores through which leaves exchange gases.

Carbon dioxide is released during photosynthesis.

Which part of the plant takes in carbon dioxide from the air for photosynthesis?

Plants take carbon dioxide from the atmosphere mainly through their: