Day 97 – Really, Why Do Things Float?

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Science 8 – In my other science 8 class we have finally got to the point of answering the question as to why things float. We know that density is a test/predictor as to whether an object will float but now that we’ve discussed forces we can say why something floats – buoyancy.

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Day 78 – Density

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Science 8 – First we started by me dropping different materials into water and the class yelled out if they thought the object would sink or float.  Good times. I then wrote a statement that summarized what they saw (I make no apologies into guiding their inquiry towards the required learning objectives).

“Not everything floats”

From this, we went around the class and had students come up with a question related to the above statement (the QFocus). The next task was to start investigating a question or two.  Lots of kids had some ideas on what density is, but no one was brave enough to offer a definition, so we started with “what is density?”

Students were put into random groups and given an object.  They were asked to find the mass (using a triple beam balance), volume and the ratio of mass to volume.  We summarized the information and then I asked students to use google to find what material that had, and to communicate this.  Students handed in their written answer, and I’ll give feedback on how well they communicated their claim and evidence.  Sounds pretty sciencey, no?

Some groups had a difficult time matching their density to a material.  The problem was in their measurement of volume.  We finally came back to the challenge from last day.  An error of 3mm on a size of 1cm results in big errors… I asked the kids to calculate the volume of w x l x h for…

  1. 20cm x 10cm x 1cm =
  2. 20.3cm x 10cm x 1cm =
  3. 20cm x 10.3cm x 1cm=
  4. 20cm x 10cm x 1.3cm =

We now know which measurement is more sensitive!

Finally, students gave self-assessment feedback on how they’re doing with density.

I had a student teacher observing this class.  She noted that it was chaotic and loud, but that she was amazed at how much kids can produce with so little specific directions.

Exactly.