Reaching the age of adolescence. — Science STD 8 — Question

What precautions should be taken in sowing the seeds?

State one way in which the air pollution caused by the burning of fossil fuels in transport and industry can kill the fish living in a lake and one way in which the water pollution caused by an agricultural activity can kill fish living in the same lake.

What happens when a copper vessel is exposed to moist air for a long time?

What are the various ways in which communicable diseases can occur and spread?

The cytoplasm of the cells of a tomato plant contains organelles X having different pigments which impart different colours to the leaves of tomato plants and its fruits.

1. What is the general name of the organelles X?
2. What is the (i) name (ii) colour, and (iii) function, of organelles X present in the leaves of Tomato plant?
3. What is the colour of organells X which are present in the ripe fruits of tomato plant?

What is electrolysis? Explain why, in the electrolysis of water, 'acidified water' is used.

What is the difference between a star and a shooting star?

What will happen if the natural habitat of a wild animal is destroyed?

How do metals react with dilute acids? Explain with the help of an example.

Name the gas produced when aluminium foil reacts with:

1. Dilute hydrochloric acid.
2. Sodium hydroxide solution.