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Density Mission (Save Paul the Ping-Pong Ball)

Paul the Ping-Pong Ball

Physical Science Activity:  Liquid Flax

A simple density activity that shows items can sink or float in materials other than water. (Density is the amount of stuff (matter) in an object. Density = mass/volume (d = m/v))


To introduce the activity have the students watch the following videos.

Ping Pong Mission (Density)

Ping Pong Mission Complete (Density)

Liquid Flax can be presented as a standalone class demonstration or it can be expanded into a class activity, depending on the amount of time available. I usually present this demonstration as a science magic trick. I announce that I will place a metal ball into a bucket of beans/flax and make it disappear. The demonstration is shown in the videos below and also described in the following lesson plan. (Lesson Plan - PDF and Demo Card: Demo Card - PDF)


Expand the Demonstration:

  • Try different grains.
  • Test other items to see whether they sink or float in your grain of choice.


Agriculture Related Topic: Grain Bin Hazards 


Related Activities

Physical Science Demonstration: Liquid Flax (Educator Explanation)

Physical Science Demonstration: Liquid Flax