Question

how can we test a substance is acid or basic.........

Answer 1

we can test it with the help of litmus paper(blue or red).
if  it is basic it red to blue.
if it is acid it turns blue to red.

Answer 2

We can test nature of a substance by red and blue litmus paper . if the solution is acidic the blue litmus paper turned into red and red litmus remains constant . if the the solution is basic in nature the red litmus paper turned into blue and blue litmus paper remains constant