Convective Heating
Energy and Thermal Physics

Convection currents in a beaker of liquid

Practical Activity for 14-16 PRACTICAL PHYISCS

Class practical

Observing convection currents in a beaker of water.

Apparatus and Materials

For each group of students

  • Bunsen burner
  • Tripod
  • Glass tube, approximately 150 mm long x 3 mm internal diameter
  • Pyrex beaker, 600 ml
  • Potassium manganate VII crystals

Health & Safety and Technical Notes

Read our standard health & safety guidance

You need to get the potassium manganate VII crystals into the beaker of water without colouring it unduly. Put a glass tube into the beaker so that it rests on the base of the beaker. Then drop the crystal through the tube.


  1. Fill the beaker with water. Put individual crystals of potassium manganate VII on the bottom of the beaker, using the method suggested above.
  2. Heat the water gently over the Bunsen burner and observe the motion of the coloured water. For a clear effect, use a small flame and no gauze between Bunsen and beaker (Pyrex beakers do stand this).
  3. Note the path that the coloured water takes from the heater to the top of the water and back down again.
  4. When repeating the experiment you should always start with a new batch of cold water.

Teaching Notes

This experiment was safety-tested in August 2007

Convective Heating
is a special case of Heating
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