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Earth and Environmental Science 11–12 · Year 12

Thermal expansion of water: measuring the rise in a flask and scaling to sea level

Module 7: Climate Science

Practical, model not builtLow risk

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The idea

Warmer water occupies more volume, so a warming ocean rises even before any ice melts, and the effect is measurable in a flask with a narrow tube.

What you need

  • 250 mL conical flask filled with coloured water, a bung with a thermometer and a 5 mm bore glass or clear plastic tube (UCAR activity)
  • lamp or a warm water bath, ruler, marker, stopwatch
  • NIST Chemistry WebBook water density table for the calculation

How to do it

  1. Mark the water level in the tube and record the temperature.
  2. Warm the flask gently (lamp or bath) and record the level and temperature every 2 minutes until the temperature has risen 10 °C.
  3. Plot the level against temperature and read the rise per degree.
  4. Calculate the expected rise from the density change and the tube bore and compare.
  5. Scale the fractional expansion to a 4000 m water column to see the order of magnitude for the ocean.

What you should see

Water density falls from 998.21 kg/m³ at 20 °C to 995.65 at 30 °C (NIST), a 0.257 % volume increase; 250 mL expands by 0.64 mL, which in a 5.0 mm bore tube is a rise of 3.3 cm, easily read against the ruler. The same fraction applied to a 4000 m column would be about 10 m, an upper bound since only the surface layer warms; the point is that the sign and scale of the effect are real.

What changes

What you change
water temperature
What you measure
height of the water column in the tube
What you keep the same
  • flask volume
  • tube bore
  • same flask and bung
  • reading at the meniscus

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

  • Sea level rises only because ice melts.
  • Water always expands when heated (below 4 °C it contracts).

Safety card

Low riskLearners carry it out

Hazards

  • warm water
  • glass tube

Controls

  • warm slowly
  • protect the tube when inserting the bung

Note

Heat or hot water is used: follow the NSW Department of Education Chemical Safety in Schools (CSIS) package, Section 1, and record a RiskAssess risk assessment before the lesson.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

  • Earth and Environmental Science Stage 6 Syllabus (2017), NESA; current, replaced by the 11–12 Syllabus (2025) from 2028EES12-14EES11/12-1EES11/12-6EES11/12-7
  • Earth and Environmental Science 11–12 Syllabus (2025), NESA; to be implemented from 2028, not yet taughtEES-12-03
  • Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.

  1. www.nsw.gov.au/education-and-training/nesa/curriculum/science/earth-and-environmental-science-stage-6-2017
  2. scied.ucar.edu/activity/thermal-expansion-water
  3. webbook.nist.gov/chemistry/fluid

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