Structure and motion of matter (SAMM) survey

The structure and motion of matter (SAMM) survey is a 15-minute, open-ended formative assessment tool that probes how students think about the structure and dynamics of a gaseous mixture. It has been tested in middle school, high school, and university chemistry classes, in both English and Spanish. The SAMM survey presents three scenarios that involve a perfume or other scented volatile substance being released on one side of a room and detected by a nose on the other side of the room. Students are asked to draw how the perfume and air molecules behave, and explain in writing both the molecules’ behavior and why they behave this way. The survey can be downloaded below in color but it usually is provided to students printed in grayscale. Resources for teachers and science education researchers include a scoring guide (for manual scoring), and a programmed Excel sheet (Windows only) for computer-aid scoring of students’ responses. Sample data sets and a norming practice guide will also be available soon. More information about what can be learned in using the SAMM survey with students can be found in this brief summary of research findings from several studies we have carried out using the SAMM survey.

The SAMM survey is © 2010 by Marilyne Stains and Hannah Sevian. Science teachers who wish to use it for teaching have permission to do so if they acknowledge the authors and comply with the fair use of this copyrighted and registered work. Likewise, science education researchers have permission to use the SAMM survey if they comply with fair use, acknowledge the authors, and cite the article listed below.

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Additional resources:

 - In this paper, the research-based process of developing the survey is described. Figure 1 from the paper, shown here, describes the process of capturing students’ thinking. Four independent variables are able to be measured by the SAMM survey, and a student’s chemical thinking in each of these can be characterized by the underlying assumptions that are both guiding and constraining the student’s reasoning:

  1. Structure of the solute (perfume or other scented volatile substance)
  2. Structure of the medium (air in this case)
  3. Origin of motion of the solute/perfume
  4. Trajectories of solute/perfume particles

 - In this book chapter (which we can send to teachers or researchers upon request by email), we described each of the implicit assumptions along the four progress variables above that can be measured by the SAMM survey. We found that most assumptions are present in populations of students at every educational level from grade 8 through undergraduate completion. Generally, students grow to rely on more conceptually sophisticated assumptions as their training in chemistry increases. The curriculum used can greatly influence how students reason. For example, in the population we studied, grade 8 students were learning for one-third of the year from a curriculum that emphasized molecules and the particle nature of matter, while the high school curriculum focused on more quantitative descriptions of matter (e.g., stoichiometry, gas laws). Grade 8 students tended to rely on more sophisticated assumptions than most high school and even many university students.

 - This paper describes five mental models students hold about the phenomenon of diffusion in a gaseous mixture. These were determined by cluster analysis of the implicit assumptions characterized using the SAMM survey with a large set of data collected from students in grade 8 through undergraduate education in sciences. (Please email us if you’d like to receive a copy of the paper.) The mental models are:

  • Mental model 1: The process of diffusion is unclear. Most students who hold this mental model think that air is a continuous medium, and that perfume molecules move but they cannot say how, nor do students express any ideas of where a perfume molecule’s ability to move comes from.
  • Mental model 2: Diffusion of perfume in air is a direct process in which air causes and controls perfume molecules’ movement. All students who hold this mental model think that perfume molecules do not move by themselves, and are controlled by air. Most students holding this mental model also think that the motion of perfume molecules is caused by external forces (e.g., wind, air pressure, inhaling by the nose, a difference in concentration in different parts of the room). About half the students also consider air as continuous.
  • Mental model 3: Diffusion is a direct process in which air controls a perfume molecule’s movement. All students who hold this mental model think of the origin of the perfume molecule’s motion as being conditioned by features of the perfume molecules (e.g., something in them that makes motion possible such as size or electrons or certain atoms, whether they are in the gas phase, a desire or natural tendency to move, the act of changing phase). In addition, all students holding this mental model think that perfume molecules move, and that the air controls their movement. About two-thirds of students also consider that air is continuous.
  • Mental model 4: Diffusion occurs through random motion. The defining feature of this mental model is that students focus on the random trajectories of perfume molecules, often talking about the collisions of perfume molecules with other molecules. Students holding this mental model have a variety of assumptions about what is the origin of motion of the perfume molecules and what is the structure of air.
  • Mental model 5: Diffusion is an emergent process. Students who hold this mental model consider that a perfume molecule’s trajectory is based on random collisions with other molecules. The majority of students holding this mental model think of the origin of motion of the perfume molecule as conditioned by properties or features of the molecule (usually size, shape, mass, and elements in it), and they consider air as submicroscopic (i.e., made of particles, not continuous).

 - In this study, students enrolled in two large university chemistry courses learned about kinetic molecular theory in different context-based learning environments. In one course, a second-semester general chemistry course, students learned through a whole-class kinesthetic activity as a large human model of a gas while focusing on a problem of differing weights of balloons at the same temperature and pressure filled to the same size with different gaseous substances. In the other course, a first-semester general chemistry course, students manipulated molecular dynamics simulations while focusing on the problem of separating CO2 from the atmosphere in order to reduce the causes of anthropogenic climate change. The SAMM survey was used as one measure to examine how students’ ways of thinking about matter structure and dynamics changed in the two contexts, and the extent to which each context influenced students’ transfer of learning about matter structure and dynamics. We found that students in the kinesthetic activity context increased in sophistication of assumptions about particle trajectories, while students in the molecular dynamics context developed more sophisticated mechanistic reasoning and understanding of particle trajectories. Students in the molecular dynamics context also gained more fluidity in the use of scientific vocabulary.