1. QUESTION:
Consider the pictorial representation shown below for a change in physical state at the molecular level. The picture best represents which of these changes: A. evaporation, B. melting, C. sublimation, D. condensation
Consider the pictorial representation shown below for a change in physical state at the molecular level. The picture best represents which of these changes: A. evaporation, B. melting, C. sublimation, D. condensation
Let’s examine the figure. The main the difference between the before and after pictures is that the molecules are closer together in the after picture.
CLICK
The average distance between molecules is significantly larger in a gas compared to a solid or liquid.
CONTINUED ON NEXT SLIDE

2. or Gas  Solid (deposition; opposite of sublimation)
QUESTION:
Consider the pictorial representation shown below for a change in physical state at the molecular level. The picture best represents which of these changes: A. evaporation, B. melting, C. sublimation, D. condensation
Molecular interpretation of phase change: Average distance between molecules decrease from Gas  Liquid (condensation or liquefaction, opposite of evaporation or vaporization)
or Gas  Solid (deposition; opposite of sublimation)
Therefore the process being represented here must be either a transformation from gas to liquid
HIGHLIGHT
Which is called condensation or liquefaction,
…or
A transformation from gas to solid,
which is called deposition.
Choice A, evaporation, the transformation of a liquid to a gas, is the opposite of condensation.
CROSS OUT choice A
Choice C, sublimation, the transformation of a solid directly into a gas, is the opposite of deposition.
CROSS OUT choice C
Choice B, melting involves the transformation of a solid to a liquid does not involve a significant change in the intermolecular distances.
CROSS OUT choice B

3. Video ID: © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08