Izvleček
V prispevku je prikazana eksperimentalna vaja, s katero učenci raziskujejo obnašanje ledene kocke v vodi in v jedilnem olju. Izvajamo jo z učenci, ki že imajo znanje o vzgonu. Vaja zgolj z uporabo preprostih, vsakdanjih pripomočkov omogoča raziskovanje fizikalnih konceptov, ki so sicer v učnih načrtih prisotni le v manjši meri, vendar imajo velik pomen v naravi in pri vsakdanjih opravilih. Eden takšnih konceptov je površinska napetost. Z eksperimentalno vajo učenci preverjajo razumevanje vzgona, spoznajo učinek površinske napetosti v smislu lepljenja in raziščejo vpliv dodajanja surfaktantov. Izkaže se, da led ob postopnem dodajanju detergenta spreminja orientacijo, način spreminjanja pa je odvisen tudi od gostot posameznih uporabljenih snovi.
Abstract
Buoyancy and Surface Tension
This paper presents an experimental task in which students investigate the behaviour of an ice cube in water and cooking oil. It is conducted with students who are already familiar with buoyancy. Using simple tools, the task allows the exploration of physics concepts that receive limited attention in the curriculum but are significant in nature or in everyday life. One such concept is surface tension. Through this experiment, students test their understanding of buoyancy, learn about the impact of surface tension in terms of adhesion, and investigate the effect of adding surfactants. The results indicate that an ice cube changes its orientation progressively when detergent is added, with the specific change depending on the densities of the substances involved.