Backwards planning your PBL unit ­ An Overview of an Entire Unit

Backward Design PBL

Last month, I described in my blog how I got into PBL and the happy story about how everything always goes perfectly in my classroom (oh, where’s the sarcasm font when you need it?!!?!??!). Over the last month, I've been thinking on and off as to how to continue this mini series on my experiences in PBL, and I thought I would give an overview of what a PBL unit has looked like in my classroom and then dig deeper into different pieces I have below - I really hope that you post questions that I can respond to!

Last month, I summarized PBL as this:

  • PBL poses an authentic problem with multiple solutions.
  • PBL requires core subject knowledge to propose solutions to a problem to an authentic audience.

I’d like to expand on this with a diagram I made that helps me organize my PBL unit (probably a mash up of a zillion diagrams I’ve seen over the last 6 years):

Figure 1: Structuring my PBL unit

This cycle really helps me think about how I might engineer a PBL unit.

  • First of all, is my task really interesting? Is is respectful to learners - aka, is this too easy or non relevant? (Read an overview based on work by Carol Ann Tomlinson.
  • Do students actually have to learn new content, or can they google the information or rely on only a few teams member to do the “heavy lifting”
  • How am I making sure students are individually accountable for learning goals? How am I making sure that the groups are accountable for learning goals? Balance is tough but really important to maintain rigor and equity.
  • And, possibly most importantly, can STUDENTS MAKE THE CONNECTIONS between the task and the core knowledge? My very first project I developed was a big fat flop because while the project was cool, I did a terrible job helping students make connections between the content and the task...more on this flop in a future post.

I digress. Here’s a little background to resources for you to look at below. If I get inspiration for a project (remember, I had a Flinn kit as mine), I typically use the write up from my inspiration to help me make the task I give my students. I had coffee with a friend who works in marketing at a pharmaceutical company, along with a pharmacist on his team, help me make the context more authentic yet keep my parameters (It pays to be vocal to people about your work! You never know what might happen!). After the first draft of the task, I revisit my learning goals and make tweaks. Then I look through lessons I’ve used to help students learn content they need to accomplish the task. I’m very intentional - some stuff I WANT them to have to do research on, such as what a hydrate is or some cost benefit analysis research. Some stuff, like the stoichiometry, needs lessons from me. I use this to make a backbone timeline, alternating between project work time and lessons from me. Then, I go back to the original task I wrote for students and try to align as best as I can and attempt to make rubrics (but I’m always tweaking as the project goes along).

Here are some sample products from my end as an overview of one teacher’s agony.

Figure 2 contains the learning goals for the unit. Note: The whole project has more content from earlier units spiraled in, but this is the new content they have to learn.

Item #1 is the letter I give my students after showing them a video from one of the people who will eventually come in to grade final presentations. If you buy materials from Flinn Scientific, you might notice that it is based on an awesome kit I found (I pride myself in not reinventing the wheel and do my best to give proper credit). This is available to registered users only when they are logged in. Please do not post elsewhere. Posted below.

Item #2 is the calendar I gave to my students the second or third day of the project. We had end of year PARCC testing to navigate through, which is the nice way of saying it was a nightmare to make. However, I have no regrets because this calendar really alleviated anxiety of students - they could see that I was being as fair as I possibly could as they were missing class (hence the “duplicate” lessons). Posted below.

Finally, I have a few closing questions for you at the end of the post, so please keep reading! 

Figure 2: Learning Goals for Stoichiometry Unit (this is shared with students - I print it out for them and they use it as a “divider” in their notebooks to denote a new unit)

Essential Questions:

  • How can we use stoichiometry to understand reactions?
  • What is the meaning of mole ratio?
  • What are the meanings of limiting reactant and excess reactant?
  • How can we use stoichiometry to understand how "good" or "useful" a reaction is with percent yield and percent error?

Toxins 5 Objectives:

  1. Define a mole ratio.
  2. Explain how to combine reactants in order to make the most product from a reaction.
  3. Identify a limiting reactant.
  4. Complete stoichiometric calculations for a variety of chemical reactions.
  5. Complete stoichiometric calculations involving limiting reactant.
  6. Calculate percent yield when the actual yield is known.



Closing thoughts: I do one of these types of projects each semester because it takes a ton of time even if there aren’t a huge number of content learning goals, and to me it is worth it even though it comes with a cost. I have made difficult decisions on content to cover. In general chemistry, I do not do any thermo, redox, or nuclear chem. Only my level 2 students (honors + anyone in my gen chem class who needs more of a challenge) get an intro to equilibrium and learn electron configurations. Fortunately, I teach AP chemistry as well, so I’m able to keep a coherent storyline from year 1 to year 2.

As you can see, this project took us right up to the end of the school a perfect world, I would have had another day for students to really practice limiting reactant and percent yield, and maybe another to have students reflect on the test before finishing their projects, but we just didn’t have time. I share this agonizing with you hopefully as an encouragement. This year was my second year working this project and definitely made some improvements that I think impacted student quality. It is still a work in progress, and even with these downfalls, students overall felt great ownership over the project, made great gains in their understanding of practical applications of stoichiometry, and had awesome presentations.

Things I would love to know from you:

  • How well do my learning goals for the unit align with the project aims?
  • Do you think this calendar made this experience more or less real world?
  • Have you learned lessons in structuring a PBL unit that you’d like to share?
  • I’ve done this project with my students for two years. Do you have ideas for me to “shake this up” so it doesn’t get stale?
  • What do you want to know next in my journey? I’d love to hear what you’d like to know, general comments about what I’ve shared so far, or your wonderings as to how I got students from point A to point B. 
Join the conversation.

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Comments 3

Rhonda Frazier | Fri, 07/22/2016 - 10:03

Wanted to take a look at the links to the PDF in the article, but I'm getting a failure to load each time. Have they been removed? Would love to take a look at them.


Deanna Cullen's picture
Deanna Cullen | Fri, 07/22/2016 - 18:45

Hello Rhonda, Thanks for checking. If you try downloading using a different browser like Safari or Chrome, you should have better luck. Please let me know if you continue to have trouble. 



Doug Ragan's picture
Doug Ragan | Sat, 07/23/2016 - 07:03

Thank you for explaining the process of taking a lab/kit and making it PBL. I am familiar with this and now hope to include it in my lesson plans. Thanks for the ideas and files.