Floating and sinking

Worksheets and lesson ideas to challenge students aged 11 to 16 to think hard about floating, sinking and upthrust (GCSE and Key Stage 3)

Heavy objects sink, light objects float – right? You can have lots of fun teaching students about why objects float and the opportunity to address many of their prior conceptions. This demonstration below is a great way to set up some cognitive dissonance when students see that some heavier objects float! Click here for some other lovely demonstrations on floating and sinking and make sure you check out our page on density.  

Does a cannon ball float?

This is a great video, showing a cannon ball floating in a pool of mercury. Depending on the age of the students, you could get them to calculate the density of the cannon ball and the density of the mercury. If you then compare the density of mercury to water it should hopefully enable students to understand why objects float in one liquid but sink in another.

  1. Air resistance
  2. Floating and sinking
  3. Moments
  4. Newton’s laws of motion
  5. Pressure
  6. Weight, gravity and free fall