What are chalcogens? Why are they so called? 

What are vitamins ? Why they are called essential nutrients ? What is their role in the human body ?

What is blister copper? Why is it so called?

What is a pesudo - order reaction ? Why is it so called ?

Draw a lake showing different zones. Why are they called so?

Give examples of " photosensitive substances " . Why are they called so ?

What is Global grain ? Why it is called so?

What are synthetic fibres? Why do we call them so? How are they manufactured?

What are the different types of bone structures shown here? Why they are called so ?

Which compound of boron is called inorganic benzene? Why is it so called?