Determining Heater Ratings Experimentally - Day 2

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Students will consider the assumptions made during the previous lesson and enhance their empirical approach.

Big Idea

Scientists confront assumptions and reconsider their approaches.

Warm-up: Confronting Assumptions

15 minutes

As we continue with our second day of this investigation, my goal is to get my students to think about our mental model of the way energy flows from the heaters to water and to consider whether it is accurate.  As we have spoken about the assumption that the beaker and water temperatures will track with one another, my intent is to get students to recognize that we can test that assumption and modify our thinking based on the results of those tests.

As class begins, I  have the following questions on the board:

A) What are we assuming about the relative temperatures of our water samples and the beakers?

B) Are we taking that assumption into consideration when we compute our heater ratings?

C) Suggest ways that we could actually TEST that assumption . . . 

I ask students to use a think-pair-share approach to get the conversation going.  It's my hope that students will see that (or perhaps wonder if . . . ) we have ways of not only measuring the water temperature but the beaker's temperature as well.  Today's work can incorporate this new thinking!

Lab Report Writing Tips

15 minutes

In the previous lesson, I distributed the immersion heater lab prompt.  Within that document there are expectations for writing a lab report, along with an assessment rubric.  My goal, in this segment of the lesson, is to preview the expectations and the rubric, as this is the first writing exercise of the year.

Students are often anxious about the expectations associated with a written lab report.  To alleviate anxiety about this, I show them a flow chart (method for exploration and writing) of how a scientific investigation proceeds.  It is my contention that a student lab report should flow in virtually the same way:

- Introduce the question at hand

- Discuss the approach

- Show a single, sample trial, from raw data point to calculated answer (in this case, a graph showing the slope which then can be used to calculate the heater rating)

- Share a summary table (here's the only deviation from the process . . .  no need to show the same calculation multiple times) of the results, along with any appropriate analysis (averages, error bars, etc.)

- End with a conclusion and statement of relative confidence

I also review the rubric that is part of the handout.  It stresses three fundamental aspects of higher-order thinking: articulation of the background ideas necessary to follow the argument, the presentation of examples or evidence, and clear and sound reasoning.  I want my students to be comfortable with this rubric as it will be featured throughout the year with a variety of assessments.

Final Data Collection Time

50 minutes

Students have the remainder of class to do multiple trials using their most sophisticated approach.  As a minimum, groups should:

- complete multiple tests of their heater, with a variety of volumes of water, and

- complete one or more tests done with the water and beaker temperatures measured independently. 

My role is to circulate from team to team providing support for teams that are struggling, redirecting teams that are off-task, and asking probing questions to stimulate deeper thinking about the investigation.  

At some point during this time, teams should take copies of their Logger Pro graphs and convert them to images in Word documents to be shared with all teammates via Google docs. Each student is expected to write her own report, based on the common data.

This work represents a time for synthesizing the ideas of the past few days - mathematically modeling of a physical system, using best practices for data collection, and engaging in positive collaboration. Students collect data and convert files as necessary and, with about five minutes left in class, clean up and return materials to the storage area.