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.
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.
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.
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.
Identify Major 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.
Evaluation and Observation
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.
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
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.
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
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.
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.