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Peer Review

Happy Molecules



Overall Numeric Rating:

4 stars
Content Quality: 4 stars
Effectiveness: 4 stars
Ease of Use: 4 stars
Reviewed: Jan 16, 2002 by Chemistry Editorial Board
Overview: Very clever demonstration of reversibility by watching motion of a mixture of
molecules in a box. After having seen the animation, the site offers an
explanation for the Boltsman's paradox. It is an excellent start for a statistical
mechanics course. However, the instructor must provide much more data and
method for the discussion of such systems.
Type of Material: Animation
Identify Major Learning Goals: Demonstrate Boltzmann's Paradox and getting students to think about the applet
Target Student Population: Physical Chemistry (Statisical Mechanics)
Prerequisite Knowledge or Skills: Some knowledge of general physical chemistry and gases is useful.

Evaluation and Observation

Content Quality

Rating: 4 stars
Strengths: Really intriguing presentation of reversibility.
Concerns: There is really no flexibility in the content. This is however an intriguing simulation that drives the user towards the content discussion.

The lack of collisions and the disappearing of molecules at the edge of the box is disconcerting. While it may be imperative for the points presented, it diverts unnecessarily from physical reality. There must be a way to make the same effective presentation without this dilemna.

Potential Effectiveness as a Teaching Tool

Rating: 4 stars
Strengths: The stunning convergence of seemingly random motions is a sure motivator of discussion and learning.
Concerns: This is a fairly difficult concept to get across to students and the disappearing molecules in the simulation detract from the explanation. Otherwise, it promises to be a fascinating simulation. Collisions between molecules didn't seem to be as common as I would have expected. There didn't seem to be glancing collisions etc. So the model is a little deceptive.

The disappearing molecules, collisions etc. should be included.

Ease of Use for Both Students and Faculty

Rating: 4 stars
Strengths: Demonstration of reversibility . very cleverly done
Concerns: It would be better not to have to use the BACK button on the browser. This is a wonderful simulation. The biggest problem is that the molecules 'disappear' when they hit the edges of the box. There is no recoil for many. This makes the simulation somewhat misleading.

There are concerns about disappearing molecules, inability to trace just one molecule, colors of molecules changing and or appearing from nowhere. The navigation buttons at the top of the 'what's going on' page lead the user into other areas. As a result the user becomes lost.