# Schreinemakers Analysis - Problem #3: Analysis of an Invariant Point (Mg-Zo-An-Gr-Pr-Ky)

Dexter Perkins
,
University of North Dakota
Author Profile

#### Summary

This is a challenging Schreinemakers analysis problem.

Used this activity? Share your experiences and modifications

## Context

#### Audience

I use this in my Petrology class as either an in-class exercise or as homework. It is NOT simple for some students and, so, may be best done in a group.

#### Skills and concepts that students must have mastered

They need to know the basic Schreinemakers process and logic. They also need to be able to identify and balance reactions in a complex system. (I let them use a Gauss-Jordan-Reduction program for this purpose.)

#### How the activity is situated in the course

My petrology class is a studio class and so group activities and in-class work are key. This is one of many exercises the students do during the semester.

## Goals

#### Content/concepts goals for this activity

The goal is to get them to (1) be able to do a Schreinemakers analysis, and (2) understand the significance of invariant points and stable/metastable equilibria.

#### Higher order thinking skills goals for this activity

Thinking, logic, reasoning, and deduction are involved. -- this problem sometimes stumps students who are looking for a cookbook approach. Accuracy and care are essential.

#### Other skills goals for this activity

They need to be able to identify and balance reactions in a complex system. (I let them use a Gauss-Jordan-Reduction program for this purpose.)

## Description of the activity/assignment

This is a standard Schreinemakers problem: identifying the sequence of stable and metastable reactions around an invariant point. However, this problem deals with a 4-component system and phases of complex chemistry. So, Identifying and balancing the reactions is not trivial and can be a real challenge for some students.

## Determining whether students have met the goals

There are two possible results (mirror images) and it is simple to determine if students obtain one of them.