Teaching Density in the Physics/Chemistry Lab, Step 3

by John R. Walkup, Ph.D.

This is Step 3 in building an NGSS-aligned lab activity for sixth graders centered on the concepts of ratio and density.

We now use Bloom's Knowledge Dimension to outline as precisely as we can the academic content our students will learn as they conduct the lab. (For more on using Bloom's Knowledge Dimension to prepare lesson plans, see here.)

Bloom's (Original) Knowledge Dimension

Make no mistake about it, we still want students to learn things.  But what?

In their seminal revision of Bloom's Taxonomy, Anderson and Krathwohl outlined four major categories of knowledge, which they termed the Knowledge Dimension. At minimum, we should peruse each of the following four categories looking for academic content we would otherwise miss.

Factual knowledge     

To identify content that falls in this category, we simply need to ask ourselves, "Ten years from now, what do we want our students to remember by carrying out this lab?"

For the lab in question, we would likely want them to know

1. the scientific definitions of mass;
2. the scientific definition of density and the equation D = m/V.  
3. the roles of a technologist and important features of this field (types of jobs, salaries, education required)
4. the formula for calculating the mean

Conceptual knowledge  

To identify content that falls in this category, we can ask ourselves, "Ten years from now, what do we want our students to understand based on what they did in this lab?"

For this lab, we would want them to understand

1. the concepts of ratio, mass, and density; 
2. measurement precision and its relationship to significant figures; 
3. the mean and 
4. statistical variability

Note that many tricks employed to help students remember the density formula (such as a D-M-V triangle shown here) often fail to reinforce conceptual understanding. If so, we need to gradually phase students' reliance on them over time. When doing so, we turn the trick into a sensible scaffold. If not, the trick becomes little more than a crutch.   

Procedural knowledge    

Not only do we want students to understand concepts, we also want them to learn how to do things, which Anderson and Krathwohl termed procedural knowledge. We can therefore ask ourselves, "Ten years from now, what skills do we want our students to still possess on account of conducting this lab?"

First, we don't want our students to have to play a YouTube video to remember how to compute the density of a substance from its mass and volume; that is something they should just know how to do. Also, they shouldn't need to watch a video to learn how to prepare a proper report that meets a specified criteria (rubric). We also want to them to know how to select proper tools for measuring lengths and volumes and how to use them. Finally, we want them to know how to express results to reasonable precision.

Metacognitive knowledge

This category encapsulates knowledge of cognition in general, as well as awareness and knowledge of one’s own cognition. This is easily the most overlooked knowledge dimension in education, but potentially the most important because of its role in helping students "learn how to learn."

We can promote metacognitive knowledge by having students

1. track their own concerns, and illuminations while conducting the lab, 
2. formulate new questions of their own to further their understanding of what they learned during the lab, and
3. detail means for which they can answer their own questions.

To aid in prompting students to generate their own questions about the lab content, Chuck Wiederhold created the Q-Matrix.* Zaner-Bloser, Inc. has created an online tutorial on how to use the Q-Matrix in K-12 classrooms.

Bloom's (Expanded) Knowledge Dimension

While I have long leaned on the original Knowledge Dimension to identify much of the content associated with a lesson, I have found the four dimensions too broad in scope for everyday usage. I have since supplemented these four levels with three more categories of my own.  Although Anderson and Krathwohl absorbed the following into the original four-category Knowledge Dimension, I find it better that they are address individually.

Relevance knowledge    

Understand the importance of density in identifying substances; appreciate the importance of significant figures

Deep knowledge

The impact on variability when determining whether a measurement meets published values; extension of the concept of density to fluids and gases; distinguish between uniform and non-uniform density

Communicative knowledge

It is not enough to know things or know how to do things, students at some point will need to communicate their knowledge to others. This will require elevated writing and speaking skills, as well as the ability to work as a team member. The Communicative Knowledge Dimension captures the vocabulary development, writing techniques, presentation techniques, and collaborative skills needed to be an important contributor to society.

For this lab, which focuses on writing for its culminating activity, we will want students to

1. develop vocabulary on density and mass,
2. learn how to prepare an informative report
3. further enhance the teamwork skills needed to complete a task.

Note that proper vocabulary development requires us to go beyond defining words; we want them to become comfortable with the words so that they feel confident using the words in both formal and informal settings. Students therefore need to know how to spell the words, say them, write them in the context of a sentence, and any other skills needed to place the words into their working vocabulary. 

Subskills/subconcepts

While we are focusing on delivering a standards-based lesson, we also need to acknowledge that, to carry out the culminating activity, students will often need certain skills and concepts they should have learned in lower grade levels.

These subskills/subconcepts often bedevil teachers and pose as potentially the number one reason instruction drifts off grade level. But once identified, we can employ the technique of subskill scaffolding to overcome these barriers.

So, which subskills or subconcepts will our students need to employ to carry out the lab activity?

• Writing skills — Some of the students are likely to be poor writers, an important subskill deficiency for this activity. To help overcome this barrier, we can employ instructor-guided use of an online editing tool (e.g., Pro Writing Aid). Also, we can emphasize the structure of the written report and de-emphasize low-level grammar and spelling. Therefore, the use of a graphic organizer (including title, abstract, data results, and summary) is a must for this activity.
• Arithmetic — Many students struggle with arithmetic. But this lesson does not center on arithmetic, so students can use a calculator to compute (for example) ratios.**
• Unit conversion — The skill in converting units could be incoporated into this lesson at the risk of making the lesson too long. Alternatively, we can have students use online unit conversion tables or simply constrain all units to a single unit system 
• Concept and units of volume — Calculating volumes of various solid objects is best left to a previous lesson. If students failed to learn this lesson, we can scaffold these skills and concepts using a think-aloud.

Summary

Now that we have outlined the necessary content for our lab using Bloom's Knowledge Dimension, we will outline the instructional strategies one can use to deliver the above content in Step 4. To do so, we will shift the pedagogical framework to Bloom's Cognitive Process Dimension.

* C. Wiederhold, Cooperative learning and higher level thinking, San Clemente, CA: Kagan Publishing, 1995. 
** Note: A calculator is not a scaffold because it doesn't help students learn arithmetic. It is clearly a crutch, albeit an acceptable one for this activivty.. 

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Seeking training at your school or district centered on Cognitive Rigor or Depth of Knowledge?  Call me at (559) 903-4014 or email me at jwalkup@standardsco.com. 

We will discuss ways in which I can help boost student engagement and deep thinking in your classrooms. I offer workshops, follow-up classroom observation/coaching, and curriculum analysis to anywhere in the country (and even internationally).