How will you know whether a sample of cheese has become rancid or not ?

How will you prepare a sample of ND_3 ?

How will you test the purity of a sample of sea water ?

How do you know the valence of a metal?

On the basis of structure of the embryo, how would you identify whether a given sample of seeds belongs to a monocotyledonous plant or dicotyledonous plant?

How will you test whether a given rod is a magnet or not?

How will you find out whether an object is charged or not ?

How do you know the valence of a non-metal?