Teach the Earth > Petrology > Teaching Activities > Mole %, Weight %, Compositions and Projections

# Mole %, Weight %, Compositions and Projections

Dexter Perkins
,
University of North Dakota
Author Profile

This activity was selected for the On the Cutting Edge Reviewed Teaching Collection

This activity has received positive reviews in a peer review process involving five review categories. The five categories included in the process are

• Scientific Accuracy
• Alignment of Learning Goals, Activities, and Assessments
• Pedagogic Effectiveness
• Robustness (usability and dependability of all components)
• Completeness of the ActivitySheet web page

#### Summary

This is an introductory exercise intended to get students thinking about mole vs weight % and about the power and problems of projections.

Used this activity? Share your experiences and modifications

## Context

#### Audience

This is appropriate for an undergraduate Petrology or Mineralogy course.

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

It helps if students already understand how to convert from moles to grams.

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

I use this during the first week of my Petrology class.

## Goals

#### Content/concepts goals for this activity

I use this during the first week of my Petrology class. It is sort of a check – to make sure students understand how to convert form moles to weight %. Also, I use this to get them thinking about projections – why we use them and what the limits are, etc.

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

Most of this is straightforward. However, students are asked when wt% might be better to use than mole%, and are also asked to speculate on a few things before they do calculations and plotting. So, they are pushed a bit toward higher order thinking skills.

## Description of the activity/assignment

This activity is a stand-alone problem set that involves converting mineral formulas to mole and weight %. The results are plotted on diagrams, some of which require projections. Students are asked to consider when they would use such diagrams, and also the shortcomings of projections.

## Determining whether students have met the goals

We wrap up/evaluate this exercise by having a class discussion. I do not grade it.