Phase Diagrams from Kitchen Chemistry
John Brady
, Smith College
Summary
The main pdf file describes a series of lab or lecture activities using water, salt, ice, sugar, and alcohol that can be used to help students understand simple phase diagrams. The supporting pdf file contains larger images of the phase diagrams for use as a pdf slide show or for printing handouts.
Context
Audience:
This is designed for a sophomore or junior level required course in petrology.
Skills and concepts that students must have mastered:
Students should have had an introduction to phase diagrams and have taken an intro chemistry course.
How the activity is situated in the course:
This is a stand-alone exercise meant to help students understand phase diagrams.
Goals
Content/concepts goals for this activity:
The goal of this activity is to have students use and understand phase diagrams.
Higher order thinking skills goals for this activity:
Other skills goals for this activity:
Description of the activity/assignment
An ability to read and use simple igneous phase diagrams is a major goal of most undergraduate courses in petrology. Many students have difficulty attaining this goal because phase diagrams are an unfamiliar kind of graph and they are described in most textbooks with an unfamiliar language â€" liquidus, solidus, eutectic, peritectic, etc. I have found that students respond well to class activities that use concepts, materials, and terminology from their life or educational experiences outside of geology. These activities let them apply knowledge that they already have to help them understand new ideas.
Particularly useful in this regard is the concept of the saturation of a liquid with a dissolving phase, such as sugar in coffee. Indeed, I have yet to meet a college student who is not familiar with the term "saturation" and its meaning, at least in terms of sugar or salt in water.
In the following pages I have collected some phase diagrams that are helpful for discussions, problems, and other activities involving "kitchen chemistry." They can be used in many ways, depending on your class setting and the time available. Along with each diagram, I include some suggestions of how they might be used based on my own teaching experiences. Each year in my petrology course, I try to find new activities or variations to keep it interesting for me and, therefore, for the students. I encourage you to do the same and hope that you will send me new activities and kitchen phase diagrams that you discover.
Particularly useful in this regard is the concept of the saturation of a liquid with a dissolving phase, such as sugar in coffee. Indeed, I have yet to meet a college student who is not familiar with the term "saturation" and its meaning, at least in terms of sugar or salt in water.
In the following pages I have collected some phase diagrams that are helpful for discussions, problems, and other activities involving "kitchen chemistry." They can be used in many ways, depending on your class setting and the time available. Along with each diagram, I include some suggestions of how they might be used based on my own teaching experiences. Each year in my petrology course, I try to find new activities or variations to keep it interesting for me and, therefore, for the students. I encourage you to do the same and hope that you will send me new activities and kitchen phase diagrams that you discover.
Determining whether students have met the goals
Students have successfully met the goals if they demonstrate a better understanding of how to read and interpret a phase diagram.
More information about assessment tools and techniques.Download teaching materials and tips
- Activity Description/Assignment (Acrobat (PDF) 484kB May25 04)
Other Materials
- Larger versions of the phase diagrams for a pdf slide show or printing (Acrobat (PDF) 161kB May25 04).
