Sink or Float and Archimedes

I looked at the project “sink or float” project ID 20961. In this lesson students examine Archimedes and the ideas of density and buoyancy. I decided that I really like how the lesson had students return to check on their thinking but to support the SKI framework it would be good to capture student ideas at the start of the unit and have them return to that at their first check-in to see what ideas they had already changed or grown or what misconceptions had been corrected to hold a more coherent idea. I built a capturing prior knowledge page that had a series of open answer questions. I did not continue but finding a way to have these answers show up with the thoughts they gather in their Eureka baskets and then show how they can use those thoughts to better answer the questions, or demonstrate their knowledge would support the students being active constructors of knowledge.

Throughout this lesson it follows both SKI and constructivist principles. Continuing with the SKI framework as described by Linn and Slotta (2009) students show initial knowledge, work through a series of steps that regularly offer opportunities to check in and see how students’ knowledge is progressing. Also students are offered the opportunity to collect new ideas in their “Eureka” basket to hold for later use. At the end of each unit of study student reflect back on the ideas in their Eureka basket. This not only supports the SKI model but constructivist principles as students are being active constructors of their knowledge. Fosnot (2005) describes four main principles of a constructivist lesson that include: prior knowledge, focus on concept, challenge student’s ideas, and apply new ideas to similar situations. This lesson uses these principles throughout the lesson design. Students learn the fundamentals and the use them to build additional knowledge. Once the ideas of buoyancy are developed through water displacement they apply that newly constructed knowledge to volume of air. The only other piece I would add would be some work with partners to build capacity through discussion. This lesson appears to only be designed for one students walking through it at a time.

Fosnot, C.T. (2005). Constructivism: Theory, perspectives, and practice. (2nd Edition) Teachers College Press

Linn, M., & Slotta, J. (2009). Wise Science: Inquiry and the Internet in Science Classrooms. Teachers College Press, 0-97. Retrieved from


  1. Thanks for describing Fosnot’s principles here. I remember some colleagues using this ‘Archimedes challenge’ on the first day of class to get students doing good science right from the start, working in groups recalling previous courses and introducing inquiry prior to discussing principles of density and buoyancy. The activity is sufficiently approachable and sustains learner curiosity, in line with BC’s new curriculum.


    1. I love hearing that someone has used it. There is nothing better than knowing about first hand experiences and the pro and cons they encounter. Sarah

  2. Sarah,

    The addition of students writing down their initial thoughts is great – it is really helpful to see where our misconceptions lie and sometimes it is not easy to know that unless we write it down. Further, working in pairs or larger groups is great idea as well as there still may be holes in student knowledge and discussion can usually weed that out.


    1. Thanks Baljeet. Some groups may need this and some may not, it completely depends on the make up of your class. Sarah

  3. Hi Sarah

    I like the fact that you discussed the four main principles of a constructivist lesson.

    I wonder if teachers used these four principles for every science concept they are supposed to cover– how many hours would be needed? Is there enough time during the school year?

    A good next step might be tp share a student’s final project. Here is something a group of my students created over 10 years ago.

    They have over 33,000 views.


    1. Hello Christopher,
      It may vary from high school to elementary school but if led from an inquiry approach I do believe it is doable to use all four steps to each main idea grouping. We tend to have three main topics that guide us through smaller ones in elementary curriculum’s. As we start to be able to get the facts easily I do believe that learning the process is the most important part. I love the idea of sharing students final projects, it makes it much more authentic for students if they know their work will be able to be seen be a real audience. Thanks for the ideas. Sarah

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