Is it possible to liquefy a gas at any condition?

Is it possible to have a polyhedron with any given number of faces?

is it possible to open a pen cap with one finger? Why?

Is it possible to have negative value in speed and displacement?

Why is it possible to write on rough blackboard with chalk ?

Why is it not possible to see an atom with naked eyes?

For a noble gas atom is it possible to have covalent radius? Explain.

State Bohr's quantam condition.

Explain the principle of the action of a siphon. What are the conditions for its action?

Is it true that under certain conditions, Mg can reduce SiO_2 and Si can reduce MgO? What are those conditions?