Hot Rocks Lab Work - Day 2
Lesson 11 of 14
Objective: Students continue to investigate what it means to be precise through the exploration of the thermal properties of rocks.
To start this second day of a multi-day exploration, I provide a warmup problem that has students consider the connection between specific moments on a Temperature graph and the physical properties of the thermal system. By using this particular question, I can simultaneously re-frame our lab work and help students develop their mathematical thinking, particularly as it pertains to models. The graph is not only a recording of what happens in a calorimetry experiment, but a model of thermal interactions. The second question is a good example of this kind of thinking; students need to consider the elements in the thermal system and the ways in which energy moves in order to nominate mechanisms for creating large temperature changes.
I give students 3-5 minutes to consider these questions on their own and ask them to jot down their thoughts in their notebooks. After that, they will quickly "turn and talk" with a neighbor to compare thoughts before a I facilitate a large group discussion. I address each question in turn and, for the final question, take the time to provide some rationale for creating large temperature changes, namely that large changes mean that small measurement errors have a smaller percentage impact.
Students direct a large group discussion with me as a participant. The discussion is based based on the Educreations videos they viewed for homework. The links to the videos are:
My room is set up in a U-shape which is ideal for discussions like this. I begin the discussion by describing the ground rules: the speaker has the floor, the speaker yields the floor to another when done, speakers need to be alert to "new" voices to the discussion, and speakers, when possible, should try to build upon others' ideas. My first prompt is a simple invitation to share a thought from the sig figs videos that seemed surprising or an idea that seemed unclear. After that, students direct the conversation and I'm just one of the participants.
The goals are to draw out students' ideas and to give students a chance to check their understanding with others. My role is to keep the ground rules in play and to re-direct the group is the discussion runs dry or into unproductive areas. If there is widespread confusion, I step in and reset the group, possibly with remediation at the board, though I wait until the discussion is completed.
As a way of allowing students the opportunity to develop questions and to carry out investigations (two of the eight NGSS Science and Engineering Practices), I add in an element to this investigation: Student teams need to generate their own questions about the experiment.
While all teams have the same primary goal (finding the specific heat of an unknown rock), each team is responsible for creating a secondary question that can be pursued. During this class and the next, teams select and then address their secondary questions. Many teams have come to class with a few questions that they generated during the first day of the investigation.
After reminding students of this goal, I poll the room to gather those questions on the Smartboard. Often teams will have more than one and, when we finish this segment, teams can select a distinct question from the master list. Should two teams wish to consider the same question, I work with them to find ways to have their investigations proceed with some differentiation. This is important as teams present findings later and I don't want the presentations to be repetitive. I come to class prepared with a list of previously pursued secondary questions should the students struggle to generate their own. In this case, this past list proved to be unnecessary, as students generated a range of questions:
As in the previous class, students run calorimetry tests on a number of rocks which have been heated in a small toaster oven.
A class-wide spreadsheet (see "specific heat results") is available, with columns labeled by rock name, so that students can enter their specific heat results and build a large data base. Each column is the set of specific heat values generated by student teams in their calorimetry experiments.
An important aspect of this time is to help groups move toward pursuing their secondary question. My role is to help student teams move toward that goal. Each group needs to transition after contributing data to the class set, so the pace is differentiated. During this portion of the investigation, some teams move on to addressing their secondary questions, while others are still looking onto the primary question.
As this lesson ends, I remind students that there will be one more day to gather their information about their secondary question. If, after the next class, teams still require data, they need to schedule time during a free period to collect them.