Physical World – Floating and sinking
Below are links to Science Learning Hub resources for primary teachers related to floating and sinking in the Physical World strand of the New Zealand Curriculum.
Building Science Concepts: Floating and sinking
Explore the big ideas that underpin floating and sinking in this article. It is a partial replication of the Ministry of Education’s Building Science Concepts Book 37 Floating and Sinking: How Objects Behave in Water.
Will this float or sink? uses an interactive or paper-based graphic organiser to consider whether an object floats or sinks. Use it prior to a unit on floating and sinking to gauge students’ thinking and again during and after the unit as formative assessment.
These simple hands-on activities use exploration and play to observe and learn about the science concepts:
Floating and sinking – initial learning concepts
The concepts listed just above the overarching concept reflect learning at New Zealand Curriculum level 1 and show how they may build in sequence.
A pdf version of the diagram can be downloaded here.
Explore aspects of floating and sinking using some of these ideas about the salinity and denseness of water.
Water density – how does it change with temperature and salinity?
Ocean density – further explores how salinity, temperature and depth all affect the density of seawater.
Ocean salinity – learn how salinity affects the density of water and how it varies throughout the ocean.
A sinking feeling – a level 4 Connected article that introduces the concepts underpinning floating and sinking in the context of a boat race. The teacher support materials provide curriculum links and include suggestions on how the article can be used to grow science capability in critiquing evidence.
Floating ice
Water density changes with temperature and salinity. When water freezes at 0°C, a rigid open lattice (like a web) of hydrogen-bonded molecules is formed. It is this open structure that makes ice less dense than liquid water. This is why icebergs float.
Activity ideas
Buoyancy in water – students make a Cartesian diver to demonstrate the relationship between volume, mass and density.
Floating eggs – students investigate water density by floating an egg in freshwater and saltwater.
Investigating sea water – students investigate some of the properties of seawater.
Temperature, salinity and water density – use this activity to help your students visualise differences in water density.
Density – students are introduced to the concept of density. They calculate the volume of various materials to determine and then rank their densities.
I always knew I’d have a career in science – I wasn’t sure what field of science or in what way I would contribute – but the logic of science, the discovery and the quest to understand the physical world fascinated me.
Images
Images can be a great way to gather students’ ideas about floating and sinking, for example the Tip of the iceberg image shows how ice floats in salty seawater. Place an ice cube in a glass of water and observe if it floats in the same manner.
These are also good images to prompt observation and discussions:
Tip of the iceberg
The tip of an iceberg which is visible above the waterline is usually only about 1/7 or 1/8 of the mass of an iceberg. Seawater is slightly denser than ice and this means that the iceberg floats with most of its mass below the surface. In comparison a cork, which has a density of about 20% that of water, floats close to the water surface. Ice has about 90% of the density of water but the density of seawater is also influenced by the temperature and salinity.
Slide the middle button to compare the two images.
Download a PDF of the two images side by side for easy comparison.
Our Floating and sinking Pinterest board is full of related resources.
