Experiment with surface tension and convection currents

By Declan Fleming2024-12-16T06:46:00

A dish with a mottled pattern of a milky cream liquid in a clear brown liquid

Source: © Declan Fleming

Use this demonstration when teaching concentration gradients, diffusion and convection at 11–16

Staple demonstrations of key kinetic theory concepts, like diffusion and convection, can be well known. This means that some students may have already seen the demonstration you had in mind, whereas other students might be approaching a concept for the first time. This is why I like to have a few extension ideas prepared. Read the article and watch the video to see how to turn the classic convection demonstration using a crystal of potassium manganate(VII) around by creating a cold cube that floats on the surface and sets the currents flowing in the opposite direction. With even more time available and the assistance of a couple of kitchen ingredients, it is possible to show students the beautiful patterns that form when convection currents combine in 3D. Download the technician notes and use this demonstration when teaching concentration gradients, density and surface tension at 11–16.

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