Non-Fiction

Phase Transition Water/Steam: Instructions for the Steam Jack

Johannes Grebe-Ellis

The author of this experimental guide to the steam lifter was invited by the German Physics Society in 2019 to give a keynote on physics education at Waldorf schools - taking stock after 100 years at the spring conference at RWTH Aachen University. Unnoticed by the Waldorf educational public, Wilfried Sommer unfolded the structure of physics block lessons, the three-part structure of the main lesson and made references to current research on physics didactics.

The highlight of his talk was a gripping presentation on thermodynamics in the context of the 9th grade physics block lessons. He showed how the interplay of temperature, pressure and volume crosses a characteristic boundary in the transition to water vapor, and in the process is accompanied under certain conditions by explosive fountains or bubbling boiling, as is known from geysers.

In response to a question from the audience as to where these experiments could be looked up and learned, Sommer promised to write the matter down. The result is now available, and it contains more: The series of experiments on volume and pressure changes during evaporation and condensation, on pressure dependence of the boiling temperature of water, and on latent heat are preceded by a comprehensive set of instructions for experiments on the steam lifter. The steam lifter consists of a vertical cylinder with piston which converts the high expansion pressure of hot steam into mechanical lifting of loads. As a precursor to Newcomens' steam engine, it can be used to show how the free interaction of forces at the phase transition can be captured in pressure-resistant volumes and made technically serviceable by controlled management of the processes.

Up to this point, this may sound interesting from a physical point of view. What does this have to do with physics lessons at Waldorf schools? If you would like to have the phase structure of the main lesson (conclusion - judgment - concept) spelled out by an experienced Waldorf teacher for physics lessons, you will get your money's worth here: All series of experiments in the described lesson on thermodynamics and especially the treatment of the steam lift follow the three step 1. demonstration experiment, 2. classifying the observations and 3. evaluation. It is a pleasure to see that here a Waldorf pedagogical point of view becomes effective in a way that can convince anyone who is interested in good physics teaching. The brochure is attractively designed. With its solid design and fresh graphics, it fits in well with the greatly increased range of similar publications from the Kassel teaching materials department and shows how this company, which has been in existence for decades, is adapting to changing requirements: The text is bilingual throughout (German / English) and is up to date in accordance with the Guidelines for Safety in the Classroom (RiSU). A further volume on the subject of electroacoustics and digital communication is in preparation.

Wilfried Sommer: Phase Transition Water/Steam: Instructions for the Steam Jack. Physics 9th grade. Volume 2., 139 pages., 15 Euros, edition waldorf, Stuttgart 2021

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