Academic journal article Science Scope

Eureka! Causal Thinking about Molecules and Matter

Academic journal article Science Scope

Eureka! Causal Thinking about Molecules and Matter

Article excerpt

Middle school students like to experiment with matter and its properties, and activities that incorporate the ooze and flow of colored chemicals can capture their interest and motivate them to talk about a variety of observations. However, as teachers, we've noticed that even after our best interactive lessons, many students still hold misconceptions about matter and its properties. Some misconceptions, such as the idea that molecules cease interacting when they reach equilibrium, can persist in spite of our best teaching.

These misconceptions may persist because students rely on a common-sense type of step-by-step reasoning called linear thinking, when a more complex but less common type of nonlinear thinking is required (see Scientific Processes sidebar). Linear thinking is intuitive for students because it relates well to the sequential narratives, stories, and patterns of their everyday lives, where a single effect follows a single cause and a goal is accomplished. Many scientific processes, such as the diffusion of molecules and the transfer of heat, do not result from this type of step-by-step linear process. The following lessons help students develop new patterns of causal thinking so they can build understandings of complex, nonlinear scientific processes related to the structure and properties of matter. (Also see "Model Synergy: Combining Classic Modeling Practices and Digital Simulations to Augment Deeper Conceptual Understanding" on page 31 of this issue.)

This article outlines a unit of eight lessons that pair the Next Generation Science Standards (NGSS) (NGSS Lead States 2013) crosscutting concept of Cause and Effect Mechanisms with the practice of Constructing Explanations within core concepts about the Structure and Properties of Matter (see Connections to the Standards sidebar for NGSS and Common Core State Standards connections). The lessons begin with an introduction to matter and volume and progress to the creation of molecular models that students revise and use to make predictions about phase changes. The entire unit requires at least eight 60-minute class periods that occur over a two-week period (see Figure 1 for an overview). Alternately, the lessons could be conducted in 40- to 45-minute class periods over a three-week time period. We have used these lessons with a variety of middle school students, including English-language learners, advanced students, and mainstream special education students. The lessons are a great introduction to the study of matter and are designed to help students talk about and develop nonintuitive (contrary to everyday thinking) and nonlinear (not following a sequential chain) ways of causal thinking in order to challenge persistent misconceptions. Student Activity Worksheets, materials lists, vocabulary lists, and rubrics for all eight lessons are available with the online version of this article (www.nsta.org/middle school). For most of the lessons, students work in groups of three or four.

[FIGURE 2 OMITTED]

Lessons 1-3: Thinking linearly about volume

Volume is a good starting place for exploring and talking about cause-and-effect relationships in matter. Materials are readily available in the middle school classroom, and direct linear correlations can be easily measured and graphed using common-sense reasoning, so students are able to conduct the first two lessons with minimal teacher guidance.

Lesson 1: Comparing solid and liquid volumes

Upon entering the classroom, students notice a bag of 10 plastic cubic centimeters, a graduated cylinder, and a half-liter bottle of water (see the online version of this article for a full materials list). Students are asked to think about examples, descriptions, and words related to volume, solids, and liquids. Working with their group, students brainstorm and collaboratively create Venn-diagram posters (Figure 2) that compare and contrast solid volume and liquid volume. …

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