Superhydrophobic Sand Repels Water

Autor/in	Williams, Hollis
Titel	Superhydrophobic Sand Repels Water
Quelle	In: Physics Teacher, 61 (2023) 2, S.138-139 (2 Seiten)Infoseite zur Zeitschrift PDF als Volltext Verfügbarkeit
Zusatzinformation	ORCID (Williams, Hollis)
Sprache	englisch
Dokumenttyp	gedruckt; online; Zeitschriftenaufsatz
ISSN	0031-921X
Schlagwörter	Science Instruction; Biology; Scientific Concepts; Demonstrations (Educational); Water; Physics; Concept Formation + Suchen Sie Ihr Suchwort? Teaching of science; Science education; Natural sciences Lessons; Naturwissenschaftlicher Unterricht; Biologie; Demonstrationsexperiment; Demonstrationsmodell; Demonstrationsunterricht; Wasser; Physik; Concept learning; Begriffsbildung
Abstract	A key concept in current fluid dynamics and its applications to biology and technology is a phenomenon known as wetting. Wetting is familiar from everyday life and is simply the ability of a liquid to stay in contact with a solid surface. The wettability depends on the properties of the liquid and the solid and can be characterized by the static equilibrium contact angle ? (the angle at which the liquid--gas interface meets the liquid--solid interface). A contact angle below 90° indicates favorable wetting such that a drop of the liquid would spread over a large amount of the flat solid surface, whereas a high contact angle indicates that very little of the solid is wetted (this can be seen in Fig. 1, which shows various stages of surface wetting in terms of the equilibrium contact angle). Nevertheless, this theory generally sounds quite dry or difficult to visualize when explained to students for the first time. The theory of the contact angle also contains some controversies and has undergone some recent developments. We propose a simple classroom demonstration with superhydrophobic sand that gives a concrete visualization of "superhydrophobicity" and outline how the phenomenon can be explained macroscopically with wetting theory. There are several interesting physical effects that are due to superhydrophobicity: experimental studies have found, for example, that superhydrophobic spheres always splash when they impact a body of liquid. In terms of applications, there are various possibilities for water storage with superhydrophobic sand outlined in the chemistry literature. (As Provided).
Anmerkungen	American Association of Physics Teachers. One Physics Ellipse, College Park, MD 20740. Tel: 301-209-3300; Fax: 301-209-0845; e-mail: pubs@aapt.org; Web site: http://aapt.scitation.org/journal/pte
Erfasst von	ERIC (Education Resources Information Center), Washington, DC
Update	2024/1/01