Pollution of Air and Water — Science STD 8 — Question

Sodium is more reactive than iron. How can you prove it?

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.

Explain why, a glass rod can be charged by rubbing when held by hand but an iron rod cannot be charged by rubbing, if held by hand.

Explain why, the flash of lightning is seen first but the sound of thunder is heard a little later (though lightning and thunder take place in the sky at the same time and same distance from us).

What is Ganga Action Plan? When and why was it launched?

Why should we not let water collect anywhere in the neighbourhood?

State two differences between the artificial satellites of the Earth and its natural satellite Moon.

Anjali's grandfather was talking to her about the quality of sound produced by different musical Instruments. The instruments like sitar, harmonium, flute, etc., give us a pleasant sensation of hearing. The dholak on the other side creates a noise.
(i) Mention the name of the vibrating part of sitar.
(ii) Briefly explain how the loudness is created by dholak?
(ili) We hear a shrilling sound by flute. Explain why?
(iv) Mention the values displayed by Anjali's grandfather.

How do astronauts talk to one another on the surface of moon and why?