Earth and Environmental Science 11–12 · Year 11

Convection currents in a beaker (syllabus practical)

Module 3: Energy Transformations

PracticalMedium risk

School laboratory, not for home

In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

The idea

Heated fluid expands, becomes less dense and rises while cooler fluid sinks, the circulation that carries heat through the mantle, oceans and atmosphere.

Safety card

Medium riskA teacher supervises

Setting: In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

Hazards

open flame and hot glass
potassium permanganate stains and is an oxidiser

Controls

heat mat and tripod
safety glasses
the teacher dispenses one small crystal with a spatula; keep solid permanganate away from paper and other combustible material
do not heat the beaker rapidly

Note

Heat and a chemical are used: solid potassium permanganate is on the Chemical Safety in Schools (CSIS) Volume 2 Appendix F list of chemicals to be used with caution, whose use is largely reserved for science teachers, so the teacher dispenses it. Follow the NSW Department of Education CSIS package, Section 1 and Appendix F, read the Safety Data Sheet and record a RiskAssess risk assessment before the lesson.

What you need

1 L beaker of room-temperature water on a tripod and gauze; a candle or a small Bunsen flame under one edge only
a crystal of potassium permanganate, dispensed by the teacher and dropped down a straw to the base above the flame, or food colouring in a syringe
two thermometers or a temperature probe pair (one above the flame, one at the far side, both 2 cm below the surface)
stopwatch, clear plastic box and a cup of ice for the cold-driven version

How to do it

The teacher drops one crystal to the base directly above the heat source; light the flame.
Record the colour plume every 15 s: it rises above the flame, spreads across the surface, sinks at the far wall and returns along the base.
Record both temperatures every 30 s for 5 minutes and plot them.
Repeat with the cold version: a cup of ice against one wall of the box and colour released beside it.
Draw the circulation and label where the fluid is warmed, moves, cools and returns; relate it to mantle circulation and to a sea breeze.

What you should see

A circulation forms: colour rises over the heat, spreads across the surface, sinks at the cooler side and returns along the base. Once the loop is established the thermometer above the flame reads higher than the far one, and the learner’s plot shows how that difference develops over the 5 minutes. Cold-driven flow sinks beside the ice and spreads along the base, the mirror image (UCAR convection activity, part 3).

What changes

What you change: position of the heat source
What you measure: direction of flow and temperature difference across the beaker
What you keep the same: water volume
flame size
crystal position
thermometer depth

Common misconceptions

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

Heat rises (hot fluid rises; heat itself moves by conduction, convection and radiation).
Convection needs a boiling liquid.

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 2028EES11-10 EES11/12-5 EES11/12-6 EES11/12-7
Earth and Environmental Science 11–12 Syllabus (2025), NESA; to be implemented from 2028, not yet taughtEES-11-01
Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.

All Concept Studio activities