Density & The Earth

This lesson serves as an introductory exploration into a concept effusive throughout the curriculum - density. This is an ambitious lesson from a time-perspective, in that it asks students to complete a group-centered density "proof" (see section below), in addition to some more traditional practice problems to re-familiarize themselves with how density works in a scientific context. 

Additionally, it may be helpful to point out that these 9th graders are generally familiar with what density is, how to calculate it, and have had previous exposure to it. This lesson will be a bit advanced if your students have never really explored density as a concept previously.

[Note: For embedded comments, checks for understanding (CFUs), and key additional information on transitions and key parts of the lesson not necessarily included in the below narrative, please go to the comments in the following document: 2.3 - Density (Whole Lesson w/comments). Additionally, if you would like all of the resources together in a PDF document, that can be accessed as a complete resource here: 2.3 - Density (Whole Lesson)[PDF]. Finally, students may need their Earth Science Reference Tables [ESRT] for parts of the lesson (a document used widely in the New York State Earth Science Regents course) as well.]

Students come in silently and complete the (attached) Do Now. In this case, I use the Do Now as a strategy for reviewing material from Unit 1 that students have struggled with. After time expires (anywhere from 2-4 minutes depending on the type of Do Now and number of questions, although this one can be done in about three minutes), we collectively go over the responses (usually involving a series of cold calls and/or volunteers), before I call on a student and ask them to read the objective out loud to start the lesson.

As a general note, the Do Now serves a few purposes:

1. It serves as a general review of the previous day's material;
2. It is a re-activation of student knowledge to get them back into "student mode" and get them thinking about science after transitioning from another content area or alternate class;
3. as a strategy for reviewing material students have struggled with (for example, using this as a focused review for material that they have struggled with on unit assessments or recent quizzes); and,
4. It is an efficient and established routine for entering the classroom that is repeated each day with fidelity (I never let students enter the classroom talking. While it may seem potentially severe to have students enter silently each day, this is both a school wide expectation and a key component of my classroom. In many respects, I find that students readily enjoy the focus that starting with a quiet classrooms brings each day).

For guidance in this section, please refer to the embedded video above, where I discuss the comments and overall pedagogical resources in the Density Proof resource. As a note, feel free to modify or change any and all parts of this or the Density Notes as you see fit. I really wanted to up the rigor of this lesson and get away from some of the standardized, rote-like nature of many density lessons, and really give them a challenging problem that inevitably causes some confused faces and a bit of academic struggling. Refer to the reflection in this section for some additional insights on how I thought about how this played out in class. 

Post-density proof, I still want to give the chance to practice what they're learning in the context of real, live Regents questions (and questions that aren't inherently as challenging as what they just did!). After transitioning back into a normally arranged classroom (as opposed to the lab groups they were working in for the Density Proof), I wanted to put the Density Practice resource as a more straightforward way to have students cement the ideas they explored more conceptually in the proof above. The attached questions are all multiple-choice, and ask students to determine the density (or mass/volume) via different measurements and through different modalities (for example, deducing the information graphically). As these are aligned to the New York State High School Earth Science Regents, they can generally work with most upper-middle school and early high school lessons that are centered around density. 

Generally for this part, I have students do a handful in groups, while I circulate, and then ask them to complete the remainder as an independent practice activity. 

In this last section of the lesson, students are given independent work time to complete the Exit Ticket. Given the number of questions, they only need about 4-5 minutes, after which it is graded communally, with a key emphasis on particular questions and items that hit on the key ideas of the lesson. We then usually quickly wrap up in the same fashion - I give students time to pack up their belongings, and I end the class at the objective (which is posted on my whiteboard, in addition to being on their 'Do Now' at the start of each lesson) and ask students two questions:

1. Do you feel that you mastered the objective for the day?
2. Can you reiterate one thing you learned about ____________ (in this case, determining or calculating density, etc.)

When the bell rings, students are asked to stand, push in their chairs, and exit the room.