Academic journal article Science Scope

Investigating Change Using the Invisible-Test-Tube Demonstration

Academic journal article Science Scope

Investigating Change Using the Invisible-Test-Tube Demonstration

Article excerpt

Have you ever reached for something underwater to find that the object was not exactly where it appeared? This is because light rays are influenced by different substances (such as air and water), depending on the substances' physical properties. The word refraction is used to describe the phenomenon of light rays bending as they pass from one substance to another substance. Although many students experience the property of refraction in everyday life, research indicates they have difficulty explaining how light rays are influenced by different mediums (Driver et al. 1994). Students have success learning about refraction by examining patterns of change that occur during hands-on, minds-on science investigations. This paper describes a simple, inexpensive, engaging way to teach refraction that students will talk about for the entire school year. First, a useful teaching tool for designing science demonstrations called the PSOE (Predict, Share, Observe, Explain) model is explained. Second, I present a PSOE demonstration I use to begin teaching the National Science Education Standards content standard about "light interact[ing] with matter by transmission (including refraction)" to eighth-grade physical science students (NRC 1996, p. 155). In addition, this paper highlights the Framework for K-12 Science Education, and students engage in essential practices such as investigating scientific questions, working collaboratively to formulate ideas, and analyzing, interpreting, and making scientific claims based on data (NRC 2012).


The PSOE model

The PSOE instructional sequence is based on a model of teaching and learning called "conceptual change" and consists of the following stages: Predict, Share, Observe, and Explain (Stepans 1996). The Predict stage interests students in the lesson and allows the teacher to identify students' initial conceptions (including misconceptions). The Share stage is a time for students to collaborate, reformulate, and refine scientific ideas. The Observe stage provides students firsthand experiences with quantitative or qualitative observations, data, or other evidence. Finally, in the Explain stage, students generate scientifically accurate ideas based on data they have collected or observed during the demonstration. Using this approach, teachers can help students identify, redefine, and change their initial conceptions through observations, collaborative interactions, and scientific data. Making scientific claims based on evidence, through both individual and collaborative experiences, is a key scientific practice that cuts across science topics (NRC 2012). In addition, the PSOE instructional model can be an inquiry-based teaching approach that incorporates many of the essential features of classroom inquiry and helps students understand that evidence-based reasoning is used to construct science knowledge (NRC 2012). In summary, the PSOE instructional sequence is a simple way to make demonstrations less teacher driven and include opportunities for minds-on, inquiry-based experiences that are necessary to learn science.

The invisible-test-tube demonstration Predict

The lesson begins by having students make a prediction about how different substances, called mediums, change the behavior of light. Teachers can help elicit students' ideas about the behavior of light by asking them to think about how different mediums influence how objects appear for two different setups that will be revealed during the Observe stage of the demonstration: (1) a test tube filled nearly to the top with water submerged in a 50 mL beaker filled with water and (2) a test tube filled nearly to the top with cooking oil in a 50 mL beaker of cooking oil (Wesson brand cooking oil works well for the demonstration). At this point in the demonstration, it is beneficial to have a beaker with water, a test tube with water, a beaker with oil, and a test tube with oil available to support visual learners. …

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