Condensation Part 2: Using PCRR to Develop Consensus Models

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Objective

SWBAT deepen their understanding of condensation and evaporation by investigating a certain phenomenon.

Big Idea

Students have experienced condensation and evaporation in the past few lessons, but do they truly grasp the cause and effect relationships and patterns that emerge to help explain causation?

Overview

This lesson has students create a model to help explain the phenomena of condensation, based on the results of their experiment with the ice cube on the cup from yesterday.

This lesson assesses students abilities to demonstrate their ability to address NGSS MS-PS1-4.   

In particular, student will discuss how molecular motion is affected by temperature changes and how that impacts states of matter.

Students will develop SP2 (Developing and Using Models) and SP 7 (Engaging in Argument from Evidence).

Additionally, students will develop the crosscutting concepts of Cause and Effect and Patterns.

This NSTA resource transformed the way that I think about teaching science using models, inspiring the creation of Present, Critique, Reflect, and Refine (PCRR) strategy. 

Do Now

10 minutes

Students experienced the phenomenon of condensation yesterday, but there was not adequate time to reflect on their experiences.  I start class by asking students to explain why they think the cup with ice has more condensation than the one without ice.  This is first completed on their own and then after 5 minutes, I have students share their ideas with their elbow partner or group.

I use the strategy of guiding questions to help them analyze their results:

1) Think about what we already know about molecular motion.  Are there any patterns that we can generate from our experiences with evaporation? (CC: Patterns)

Here I am looking for students to see that, in terms of molecular motion and energy, evaporation is the opposite of condensation.  I would love for them to discuss phase changes and the factors that contribute to them.  However, if they don't delve this deep, we will investigate phase changes in the near future. 

2) Based on our experiences and evidence to support molecular motion (lessons 1.1-1.5), what explains the presence of more condensation in the cup with ice?

Here I am looking for students to make connections that gases turn to liquids when they lose energy ("get colder" is fine for now--we haven't covered heat transfer).  The ice helped slow the molecules down faster than the water vapor that didn't have direct contact with the ice. 

As students are walking around, I am asking probing questions to elicit their ideas.  Common questions sound like:

"What happens to molecules when they're hot or cold and how do we know?"

"If something touches ice, what might happen?  How do we know--what evidence do we have in our notebooks to support this?"

Students share their ideas & we develop a class model for how the condensation forms.

10 minutes

Establishing a consensus model in a class means that everyone's ideas are heard and politely challenged by their peers.  Each group has a representative stand and I maintain decorum and order, but keep my thoughts out of it.  Here is a poster that I have hanging in my room to encourage respectful discussions and comments during peer-review.

This graphic organizer explains the structure of what I have dubbed the PCRR strategy, which stands for Present, Critique, Reflect, and Refine.  

TIP: Teachers should circulate during the Do Now and pick a model from a group that has some misconceptions.  Try not to pick the best, most accurate one model.  We want kids to question their ideas, reflect and then respond to new ideas or questions.  Picking the best model as the catalyst will not result in the most fruitful classroom conversations--choose wisely.

 

Students Share New Models And Identify Aspects Needing Improvement

10 minutes

There are many options that you can use to begin the PCRR process:

1) Have groups present their models and research to the class or another group

2) Students can pass their research and evidence-based model (usually a drawing) to another group and the other group can review their argument/explanation.

3) I have had students create theatrical performances and their script was where they defended their choices for certain scenes by using specific evidence to support their ideas.  They then alter their skits based on the comments from the reviewers and reenact the skit again.

Students then give their critiques to the original student or group and the owner(s) then reflects on the comments and refine their explanations.  This can often lead to students performing more investigations, reanalyzing and interpreting their data, etc.  

I need to stress that models are used in science and our classes to help explain scientific phenomena.  Evidence is used to defend our explanations, which is derived from argumentation during the review process.  Our actual models are constantly changing.  This mimics the process that scientists go through to establish accurate models.  It is important to help students realize that scientific models evolve with the discovery of new evidence.  Therefore, it is good practice to revisit models as the year progresses, so that students can revise them.  In addition, models can be used to help students recall prior knowledge and apply what they already know to new phenomena.