Question

When you make ice cubes, the entropy of water:
A.Does not change
B.Increases
C.Decreases
D.May either increases or decrease depending on the process it used

Answer 1

Try to determine the orientation of particles in the given state of matter and determine the change in orientation of particles when it changes its state, and then compare it with the randomness or the entropy.

Complete answer:
Entropy is qualitatively defined as a measure of how much the energy of atoms and molecules become more spread out in a process and can be defined in terms of statistical probabilities of a system. For a reversible process the entropy generation is zero and the entropy change of a system is equal to net entropy transfer. The entropy balance is analogous to energy balance relation. Change of entropy can be calculated quantitatively. It can be calculated as: $\Delta {\text{S}} = 2.303{\text{nRlog}}\dfrac{{{{\text{V}}_2}}}{{{{\text{V}}_1}}}$ where n is the number of moles of gas, R is universal gas constant, ${{\text{V}}_2}$ is final volume and ${{\text{V}}_1}$ is initial volume.
Matter exists in three states namely solid, liquid and gas. These states of matter arise due to the variation in the characteristics of the particles of matter. Solids have definite shape, fixed volumes, tendency to maintain their shape and are rigid. Strength of force acting between particles of solid is so strong which helps solid to have such properties. On the other hand, liquids have no fixed volume but have a fixed volume as they take the shape of the vessel in which they are filled. The rate of diffusion of liquids is higher than that of a solid because the liquid particles can move freely because of greater space between them and lesser force of attraction between particles as compared to solid. Gas particles move randomly at very high speed due to the maximum free space between the particles and minimum force of attraction among them. Gases are highly compressible and gases show the property of diffusing maximum.
As the formation of ice cubes involve change of state of water from liquid to solid, as we have just discuss that entropy refers to randomness and a matter in solid state is more ordered than that of liquid state as particles are arranged more specifically or located in the solid state than the particles orientation in liquid state. Thus, during formation of ice cubes or when matter goes from liquid to solid, its entropy decreases.

Thus, the correct option is C.
Note:
$\Delta {\text{G}} = \Delta {\text{H}} - {\text{T}}\Delta {\text{S}}$ is the relation used to determine change in Gibbs free energy, change in enthalpy, change in entropy in single equation. If change of Gibbs free energy is positive, reaction is non spontaneous and negative change corresponds to spontaneous reaction. If enthalpy is positive and negative then free energy is never negative because if entropy is negative then the product of entropy with temperature becomes negative and the subtraction of negative value from the given positive value of enthalpy can never result in negative Gibbs free energy.