Parallel Computing in the Computer Science Curriculum > Workshops > SIGCSE 2012 > SIGCSE 2012 > Mass Balance Model

Mass Balance Model

Activity and Starting Point page by R.M. MacKay. Clark College, Physics and Meteorology.

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

For more information about the peer review process itself, please see

This resource received an Accept or Accept with minor revisions rating from a Panel Peer Review process

These materials were reviewed using face-to-face NSF-style review panel of geoscience and geoscience education experts to review groups of resources addressing a single theme. Panelists wrote reviews that addressed the criteria:

  1. scientific accuracy and currency
  2. usability and
  3. pedagogical effectiveness
Reviewers rated the resources:
  1. Accept
  2. Accept with minor revisions
  3. Accept with major revisions, or
  4. Reject.
They also singled out those resources they considered particularly exemplary, which are given a gold star rating.

Following the panel meetings, the conveners wrote summaries of the panel discussion for each resource; these were transmitted to the creator, along with anonymous versions of the reviews. Relatively few resources were accepted as is. In most cases, the majority of the resources were either designated as 1) Reject or 2) Accept with major revisions. Resources were most often rejected for their lack of completeness to be used in a classroom or they contained scientific inaccuracies.

This page first made public: Jul 19, 2005

This material was originally created for Starting Point:Introductory Geology
and is replicated here as part of the SERC Pedagogic Service.


Students are introduced to the concept of mass balance, flow rates, and equilibrium using a simple water bucket model. In this JAVA based online interactive modeling activity students can vary flow rate into the bucket, initial water level in the bucket, and residence time (lifetime) of water in the bucket. After running the model, the bucket's water level as a function of time is presented graphically and in tabular form.

Learning Goals

Context for Use

This activity is appropriate for introductory geoscience courses in which a fundamental knowledge of mass balance concepts is important.

Description and Teaching Materials

The complete activity with assignment in PDF format and online model is available at Model Activity page

Mass Balance Activity (Acrobat (PDF) 289kB Jun7 11) is the activity available for students online at Model Activity page

Mass Balance Activity (Microsoft Word 89kB Jun7 11) is an MS Word document that can be modified by you.

Teaching Notes and Tips

This activity takes about 2-hours to complete.

This activity works best with a PC, but with proper configuration also works on MAC OS X.

Little mathematical background is required to complete this activity.

Students typically have little trouble answering the first 17 questions in this activity. Students usually have to think more carefully when using the online model for the two structurally similar examples at the end of the activity (home heating and bank loan balance). Encourage them to keep units clear in their mind. For the water bucket, level is expressed in gallons and time in min; for the home heating, level is in degrees Celsius and time in hours; and for the bank loan, level is in US$ and time is in months.

I often use a 2-liter pop bottle, with flow from a hose into the top and a hole in the bottom, as a physical model during an in class discussion of mass balance and the water bucket model. The lifetime (residence time) for this water bucket model is then related to the hole size in the bottle and viscosity of the water.


Mass Balance Activity Answers (Acrobat (PDF) 292kB Aug18 04) in PDF format for easy grading.

Grading the completed activity sheet provided can be used as an assessment of student understanding. Follow-up discussions in class, essay questions on exams, and the future success of students on other related activities are also useful measures of student understanding.

References and Resources

The water bucket mass balance model described here is the first of four activities that I use in my courses when discussing Earth's Climate and Stratospheric Ozone.

The next activity in the sequence, Trace Gases , is designed to extend these fundamental ideas and the terminology of mass balance into an atmospheric science context. If you are short on time you can highlight key aspects of this activity in a lecture and then assign one or both of the related activities below.

These last two related activities can be done in any order.