Thermodynamics

Let's analyze each process in terms of entropy change ( $\Delta S$ ):I. Sublimation of dry ice (solid $C O _{ 2 } ⟶$ gas $C O _{ 2 }$ )A solid goes directly to a gas.The disorder (randomness) increases significantly.Entropy increases $\rightarrow \Delta S > 0$II. Freezing of water (liquid $⟶$ solid)A liquid becomes a more ordered solid structure.Disorder decreases.Entropy decreases $\rightarrow \Delta S < 0$III. Crystallisation of the dissolved substanceDissolved ions/molecules (disordered) form a regular crystal lattice (ordered).Disorder decreases.Entropy decreases $\rightarrow \Delta S < 0$IV. Burning of rocket fuel (combustion)Chemical reaction produces gases and increases randomness overall. Entropy increases $\longrightarrow \Delta S>0$ Processes with negative entropy change:II. Freezing of waterIII. Crystallisation of the dissolved substance Correct answer: Option B - II and III only