Question

we cannot taste all substances to find whether it is acid or basic, suggest best method to identify the substances​

Answer 1

We cannot taste all substances to find whether it is acid or basic because it can cause irritation and can even damage your skin.

So in such a case we use indicators ,

• Litmus paper is a natural indicator.It is obtained from a kind of plant known as Lichens.

        There are two types of litmus paper : Red litmus  and Blue litmus.

              =>  Red litmus turns blue when it is dipped in a solution of base.

              =>  Blue litmus turns red when it is dipped in a solution of acid.

• Turmeric  is another.It turns reddish to deep brown in acidic medium and remains yellow I'm acidic or neutral medium.
• China-rose  is another example of a natural indicator.It turns green in basic and red in acidic solution
• Red-cabbage  is another indicator which is purple in color. It turns green in basic medium and red in acidic solution.

hope it helps !!