You might have noticed that when copper powder is heated in a china dish, the surface of copper powder becomes coated with black colour substance. (i) How has this black-coloured substance formed? (ii) What is that black substance? (iii) Write the chemical equation of the reaction that takes place.

What type of questions asked from the lesson of magnetic effect of electric current 

Wavelength of green light is

A) 400-450 nm

B) 500-550 nm

C) 660-720 nm

D) 720-800 nm

What is the difference between anaerobic & aerobic respiration? Name some organism that uses the aerobic mode of respiration?

What are the main components of our environment? Explain each of them briefly.

What are examples of hydrotropism plants?