A student has performed an experiment in the laboratory. He mixed water with hexane and found 2 layers separated . Second time he mixed chloroform with water and he again found 2 layers in the test tube. Explain which one will be upper layer and which one will be lower layer in both the cases?

In first case water layer will be lower one as its Density is much more than that of  hexane due to polar nature of water molecule whereas hexane is non-polar molecule.
In second case water will be present on the upper layer sue to high density of chloroform becuase of the presence of three large size chlorine atom in it.