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MERLOT II


    

Peer Review


Gibbs Free Energy Java Applet

 

Ratings

Overall Rating:

2 stars
Content Quality: 2 stars
Effectiveness: 2 stars
Ease of Use: 4 stars
Reviewed: May 04, 2006 by Chemistry Editorial Board
Overview: This interactive applet describes the Gibbs Free Energy Equation from a
qualitative and quantitative standpoint. User can vary the values of enthalpy
and entropy to predict the spontaneity of a chemical reaction.
A java applet is presented in which the standard Gibbs free energy is plotted
against temperature for a hypothetical reaction. There is some limited
interactivity with the applet.
Learning Goals: To enable students to realize that both enthalpy AND entropy play significant
roles in determining whether or not a reaction is spontaneous at various
temperatures.
THe purpose of the applet is to demonstrate how the standard free energy change
for a chemical reaction varies with temperature and entropy in a graphical
manner.
Target Student Population: First year and physical chemistry students.
Prerequisite Knowledge or Skills: Students should have previous exposure to the Gibbs Helmoltz equation.
Type of Material: This is an interactive applet.
The site contains a small Java applet containing a graph of the free energy
change with respect to temperature.
Recommended Uses: The Applet can be used for lecture demonstration introducing Thermochemistry
and reaction spontaneity as it relates to free energy and magnitude of enthalpy
and entropy. It would also be helpful for students to work with on their own as
they study the variation in free energy with temperature and magnitude of
enthalpy and entropy.
Some instructors might find this applet useful to show how temperature and
entroy changes can influence the standard molar free energy for a chemical
reaction.
Technical Requirements: Java Plug-in is required. The author states that the Macintosh version of
Netscape may have some problems, but gives helpful pointers.
The JAVA applet function of the browser must be enabled.

Evaluation and Observation

Content Quality

Rating: 2 stars
Strengths: This applet is interactive and enables users to varie input parameters such as
temperature, enthalpy and entropy in order to see their effects on reaction
spontaneity. It provides quantitative and qualitative information.
Students can learn how changes in temperature or entropy can affect the
spontaneity of a chemical reaction under standard conditions.
Concerns: The applet is presented without any basic instruction regarding free energy or
background information on th functionality of the Applet.
Most chemical reactions do not occur at standard state conditions or
concentrations, so the real value of the site is quite limited indeed.

Potential Effectiveness as a Teaching Tool

Rating: 2 stars
Strengths: This is a good tool to introduce the Gibbs Equation and the combined effects of
entropy and enthalpy on the spontaneity of a reacion. The graphical
representation and the level of interactivity makes it a valuable tool for
introducing these abstract concepts.
The instructions do not mesh well with the operational characteristics of the
applet. For example, the user is instructed to drag the end points of the graphs
to reset the data. In fact, the user must click, drag, drop and then wait.
Concerns: Sometimes the toggling from qualitative/quantitative tabs does not refresh well
and the enthalpy and entropy boxes saturate. It would be helpful if the
qualitative boxes were more flexible so that the startup condition didn't show
the enthalpy and entropy boxes as fully saturated and unchanging.
The instructions do not mesh well with the operational characteristics of the
applet. For example, the user is instructed to drag the end points of the graphs
to reset the data. In fact, the user must click, drag, drop and then wait.
Finally, the applet will rearrange the graph. This is a disconnect that
discourages the user from continuing work with the applet. In fact, one of the
end points must be dragged from left to right, and the other up and down, facts
that are not mentioned in the instructions ..... but should be.

Ease of Use for Both Students and Faculty

Rating: 4 stars
Strengths: The applet is relatively easy to use in qualitative or quantitative mode. User
can easily interact by dragging the line plot to get system feedbacks.
Concerns: The Applet is presented without any documentation on how the Applet can be used.
Toggling from the quantitative to qualitative does not refresh at some
instances. The "Back to the Applet" text link does not work prperly (it is just
a history back button). The qualitative boxes should autoscale between certain
ranges so that they are never pegged at the maximum values.
The drag the graph function does not work well. There are few instructions
associated with the applet. For example, a return has to be entered after
numbers are specified for entropy or free energy, but the user is not told this
is necessary. A separate button 'recalculate' would help here. The drag and drop
on the ends of the graphs function does not work as specified, indicating a
poor effort at debugging the final product. The drag and drop functions have
directionality associated with them. A few instructions would save a lot of
frustration for the end user.

Other Issues and Comments: This Applet simulate the Gibbs Free Energy Equation from a qualitative
or quantitative standpoint. User can vary the values of enthalpy and entropy to
predict the spontaneity of a chemical reaction. The interface is not very
usable and unfortunately no additional information is given to help the user
figure out the functionality of the Applet.

This applet has some possibility of becoming useful, but not in its current
format. Non standard state conditions need to be allowed for. A list of possible
chemicals for the chemical reaction should be permitted along with look up
tables for these reactions. The scope is much larger than this modest applet
indicates. The user instructions need to be considerably improved.