Illustration of Second Law using clever energy transmission graphics.
Type of Material:
Identify Major Learning Goals:
Understanding energy flow and the microscopic basis of the Second Law
Target Student Population:
Physical Chemistry or advanced general chemistry students
Prerequisite Knowledge or Skills:
some understanding of thermodynamics and energy levels
Evaluation and Observation
Both the instructions and the applet are correct in content. The concepts presented are consistent with those presented in a physical chemistry text.
The spring constant and the gravitational constant can be changed. The ability to freeze the vibrational motion of the atoms and to see the effect on the height of the bouncing ball is very effective.
Since the number of vibrational degrees of freedom increases with the number of atoms it would be interesting to be able to make more complex balls with larger numbers of atoms to show the energy dissipating into more vibrations. The model proposed is for an isolated system, i.e. there is only energy transfer between the bouncing ball and the vibrating atoms. Another interesting idea might be to model the surroundings as a collection of vibrating atoms to show that energy will transfer between the vibrating atoms in the ball and the atoms in the surroundings.
Potential Effectiveness as a Teaching Tool
The major strength of this applet is that it shows microscopic behavior in objects which students can't normally see. It also illustrates how energy is transferred from the macrocopic to the microscopic and the directionality of that process. The instructions work well with the animation. Once again the author has a lively, informal writing style which makes the instructions enjoyable to read.
This applet could be used by the instructor in a classroom setting for presentation ( a lecture aid) or by the student as a part of a web-based homework assignment. Questions could be developed by the instructor which the students could answer by varying the slide controls and seeing the effect on the animation.
Ease of Use for Both Students and Faculty
The slide controls were easy to change. Their effect on the animation was easily seen.
Although the instructions say that the spring constant can be set to zero causing the atoms to fly apart,
the lowest value for k appears to be 0.2 which causes vigorous vibration in the atoms. The go button must be depressed twice before the ball will drop. The major feature of concern is that the energy display only works intermittently. It appears in the upper left hand corner of the screen and most of the time flickers rapidly making it difficult to read. Clicking the flickering display sometimes freezes it and makes it visible.