Question

H2O (l) gives H2O (g). the change in entropy in the given phase change is positive or negative. why?

Answer 1

The entropy of a system is the measure of degree of randomness or disorderliness in the system. It is a thermodynamic property and is denoted by the symbol S. For e.g. a gas is more random than liquid which in turn is more random than solid. Thus entropy for solids, liquid and gases follows the order:
Gas>liquid>solid
As the entropy of gas is more than a liquid therefore, During the phase trasformation i.e
H2O (l) $\to$ H2O (g)
The change in entropy = entropy of water vapours - entropy of gas
Hence chance in entropy is positive.