Diffusion Lab (Day #2 of 3)

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Objective

1. Students will investigate the effect of molecule size on diffusion through a semi-permeable membrane. 2. Collect evidence and use it to develop a claim and compose an argument about the permeability of an artificial membrane. 3. Use a scientific model to share and expand one’s thinking about the nature and function of cell membranes.

Big Idea

Cell membranes are semi-permeable. Diffusion of substances across the membrane is driven largely by the size of the solute particle.

Learner Goals

Note: I recommend that you first check out this resource in order to get the most out of this lesson!

In high school I took several drafting classes and, for a while, I had hoped to become an architect. With respect to planning instruction and teaching, I feel that I can still live out the detailed approach to building something intricate and complex even though the product is a lesson rather than a certain "built environment".

The lesson-planning document that I uploaded to this section is a comprehensive overview of how I approach lesson planning. This template includes the "Big Three" aspects of the NGSS standards: Disciplinary Core Ideas, Crosscutting Concepts, and Science Practices. Of course, there are many other worthy learning goals, skills, instructional strategies, and assessments that can be integrated into a class session. I don't feel compelled to check every box but, rather, use it as a guide to consider various options and tailor the lesson in light of these.

With regard to this particular lesson, students will be able to:

1. Investigate the effect of molecule size on diffusion through a semi-permeable membrane.

2. Collect evidence and use it to develop a claim and compose an argument about the permeability of an artificial membrane.

3. Use a scientific model to share and expand one's thinking about the nature and function of cell membranes.

I hope you get some value from my work! Please find the more intricate details of this lesson plan in the uploaded document!

[Note: Refer to the planning document for specific details throughout the three day investigation]

Anticipatory Set ("Hook")

5 minutes

Continued from Day #1...

Setting up the Lab: For all of my visual/spatial students, seeing is believing. And even for those auditory learners (definitely not my learning style), demonstrations can be quite powerful in explaining how to do something. YouTube's popularity just proves this point. And speaking of YouTube, here is a demo that I created to show how this lab is set up!

Students are then free to ask any clarifying questions before they do it on their own. Then, they go forth and do science! #LetsDoScience

Instructional Input/Student Activities

45 minutes

Teaching Challenge: Use a scientific model to share and expand one's thinking about the nature and function of cell membranes.

The heart of this, and any other, investigation is to lead students to the point where they can pose a meaningful scientific question, make a reasonable and testable prediction, and devise a method for collecting evidence with which to answer the original question and compose a thoughtful argument about the related phenomenon.

The main object of study in this lab is the structure and function of a typical cell membrane. Due to the small-scale size and fragility of the membrane, the dialysis tubing is substituted as the model. I sketched this to aid students in setting up the lab.

According to the details laid out on slides #3-13 of the Diffusion Lab Design PPT and lesson-planning document, students will now implement their plans. Go forth and do science!

Closure: What did we learn? Where do we go from here?

5 minutes

Review of Lab Essentials: I quickly review the essentials of the key variables for tomorrow's lab (lab question, the MV, RV, CVs, ECC) as outlined in the lesson-planning document.

As students were finishing the implementation of their lab, I interviewed some of them to support their task and to learn how they think the lab will turn out the next day. Here, a student articulates his thinking in quite a sophisticated way! 

This student is excited to learn how things turn out tomorrow! Waiting for diffusion is like watching a pot of water waiting for it to boil. Patience is difficult!

Continue to Day #3...