36.Two or more forms of a chemical element having different physical properties but rising to identical chemical compounds are called :

37.Which one of the following is a mixture ?

38.The mass of the body is different from its weight because

39.Which of the following groups of scientists provided experimental proof to the abiotic origin of life ?

40.Given below are two statements, labeled as Assertion (A) and Reason (R). In the context of the two statements, which of the following is correct ? 1. Assertion (A) : A gas filled balloon stops rising after it has attained a certain height in the sky. 2. Reason (R) : At the highest point, the density of air is such that the buoyant force on the balloon just equals its weight.