Final answer:
The physical state affects entropy changes, with gas phase increasing entropy due to higher molecule mobility and more microstates, while transitions to solid or liquid phases decrease entropy as order increases. Temperature elevation also leads to increased entropy by allowing more microstates.
Step-by-step explanation:
The physical state of a substance indeed has an effect on the change in entropy (ΔS). As a substance changes from solid to liquid, and then to gas, the entropy increases because the number of microstates accessible to the molecules increases. In the solid phase, molecules are in fixed positions and can only vibrate slightly, resulting in a lower entropy (Ssolid). When the substance melts into a liquid, the molecules have more freedom to move, which increases entropy (Sliquid). Finally, in the gas phase, molecules move freely and occupy a larger volume, leading to an even greater entropy (Sgas). Therefore, the gas phase increases ΔS, while transitions to the solid or liquid states generally decrease ΔS.
During phase changes, such as melting (solid to liquid) or vaporization (liquid to gas), the entropy increases because the molecules have greater freedom of motion, and the number of microstates increases significantly. Conversely, when a gas condenses into a liquid or a liquid freezes into a solid, the entropy decreases. This is because the system becomes more ordered, and there are fewer available microstates. Additionally, as the temperature rises, more microstates become accessible, leading to an increase in entropy with temperature. Considering these factors can help us predict the sign of entropy changes for various physical changes.