Reflection: Developing a Conceptual Understanding Marshmallow Molecules - Section 7: A Look at Student Work


Early in my teaching career, my state had a standard that stated that students should be able to identify and classify different types of matter (element, molecule, compound, and mixture).  I spent years quizzing students on lists of substances as they stated the type of matter each substance was.  For example, the list might go:

1.  Salt (NaCl)

2.  Silver (Ag)

3.  Pizza

4.  Sugar (C6H12O6)

5.  Kool Aid

After lots of practice, students would get really good at this.  They would find patterns in the questions and start memorizing.  They would memorize that salt, sugar and water were compounds.  They realized that most of the time any type of food is a mixture.  They started saying things like, "Anytime there are two capital letters or little numbers, that means it is a compound." or "If there is only one capital letter it is an element."  While these comments mean they saw some patterns, it shows little to no conceptual understanding of what makes a compound a compound or an element an element.  

One thing that I love about the NGSS is that it asks students to create models that can predict phenomena.  So, instead of saying "one capital letter", I shifted this activity so that students identify patterns at the atomic level.  Instead, when presented with a picture of the particles in any substance (no matter the name or if they are familiar with the substance), they would be able to use their models to predict the type of matter the new substance is.  Now, students say things like, "That substance has different atoms bonded together; it must be a compound."

When I started investing time in the NGSS, this was one lesson that I made big changes to.  Notice on the last page of the student sheet that for every substance that the students have to classify, a picture of the particles is provided.  This leads to the development of a conceptual understanding as opposed to memorizing.  

The more I implement the NGSS the more I commit to the idea that science learning has nothing to do with memorizing, it's all about conceptual understanding being applied with principles founded in science and engineering.  Every time I come to a lesson that I am temped to tell a student, "It is something you just have to memorize.", I know it is time to change the lesson and shift my pedagogy.

  Stop Memorizing!
  Developing a Conceptual Understanding: Stop Memorizing!
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Marshmallow Molecules

Unit 4: Physical Properties: Molecular Arrangement and Phase Changes
Lesson 1 of 12

Objective: Students will be able to develop models of elements, molecules, compounds, and mixtures.

Big Idea: Students use marshmallows and toothpicks to develop models of molecular structures! In addition, students utilize graphing to monitor their own learning.

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