Buoyancy in water
In this activity, students make a Cartesian diver to demonstrate the relationship between volume, mass and density. A similar principle is used in Argo scientific floats.
By the end of this activity, students should be able to:
describe some of the factors that affect what makes an object float or sink
understand how volume, mass and density are related
understand how Argo floats rise and sink in the ocean.
How Argo floats rise and sink
Dr Phil Sutton of NIWA explains how the buoyancy of an Argo float is controlled to make it rise or sink. This is based on changing the density of an oil reservoir. He also demonstrates a Cartesian diver, which works on similar scientific principles. This demonstration can be found in the activity Buoyancy in water.
Download the Word file for:
introduction/background notes
what you need
what to do
extension ideas.
Related content
Explore the big ideas that underpin floating and sinking in the article Building Science Concepts: Floating and sinking.
Read the articles Ocean salinity and Ocean density to learn about the vital role salinity and density play in ocean currents and heat circulation.
Activity ideas
Temperature, salinity and water density – use this activity to help your students visualise differences in water density.
Floating eggs – students investigate water density by floating an egg in freshwater and saltwater.
Investigating seawater – students investigate some of the properties of seawater.
