Science and Technology K–6 · Year 5
Rock tumbling with sugar cubes: physical weathering by the shake
Science understanding: Earth and space sciences
The idea
Rocks knocked together in a river or by waves lose their corners and shed grains, and shaking sugar cubes in a jar measures that wear as mass lost against number of knocks.
What you need
- 40 sugar cubes
- a plastic jar with a screw lid
- a sieve or tea strainer
- kitchen balance reading to 0.1 g
- hand lens
How to do it
- Weigh 10 cubes and record the mass. Look at their sharp corners with the hand lens.
- Put them in the jar, close the lid and shake 25 times. Sieve out the loose sugar, weigh the cubes that remain and record. Sketch a cube.
- Return the cubes, shake 25 more times (50 total), sieve and weigh again. Repeat at 100 and 200 shakes.
- Plot mass remaining against number of shakes.
- Repeat with a fresh 10 cubes shaken with a handful of gravel in the jar (harder tumbling) and compare.
- Relate the rounding of the cubes to the rounded pebbles in a creek bed.
What you should see
Corners round first, then faces wear, and loose sugar sand builds up; the mass of the cubes falls steadily with the number of shakes, and the loss is faster with gravel in the jar. The line of mass remaining against shakes slopes downward, roughly straight at first; the exact slope is the learner's data. The lost mass reappears as the sieved sand: the total is close to the starting mass, less the dust left in the jar, as it is when a rock weathers into sediment.
What changes
- What you change
- number of shakes (and gravel present or not)
- What you measure
- mass of cubes remaining
- What you keep the same
- number of cubes
- jar
- shaking strength
Common misconceptions
Each of these ideas is wrong, and the activity is a chance to test it.
- Rocks are round because they were made round.
- Weathering needs chemicals.
- The sugar disappears (it becomes sand in the sieve).
Safety card
Hazards
- sugar dust
- spilt sugar draws ants
Controls
- no eating
- wash hands
- sweep up spilt sugar
Note
Risk assessment before the lesson using Primary RiskAssess or the school's own template.
Curriculum references
The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.
- Science and Technology K-6 Syllabus (2017), current, taught until 2026; a Stage 2 outcome, because NSW teaches gradual weathering and erosion in Stage 2 ('investigate why the Earth's surface changes over time as a result of natural processes and human activity'), while the Stage 3 surface-change content under ST3-10ES-S covers sudden geological change and extreme weather events, its other content group being Earth's place in our solar system; code read from the syllabus document on 22 September 2026ST2-10ES-S
- Science and Technology K-6 Syllabus (2024), implemented from 2027; NESA's timeline is 2026 plan and prepare and 2027 start teaching, and schools may choose to implement it during 2026; Stage 2 content: 'Explain how the forces produced by wind, water and living things weather rocks'; code read from the outcomes page and the content read from the Stage 2 content page on 22 September 2026ST2-SCI-01
- Science and Technology K-6 Syllabus (2017), current, taught until 2026; code read from the syllabus document on 22 September 2026ST3-1WS-S
- Science and Technology K-6 Syllabus (2024), implemented from 2027; NESA's timeline is 2026 plan and prepare and 2027 start teaching, and schools may choose to implement it during 2026; code read from the outcomes page on 22 September 2026ST3-DAT-01
- Australian Curriculum v9AC9S5U02AC9S5I02AC9S5I03AC9S5I04
Sources
The pages the author read to write this activity.