The effect of the partial pressure of water vapor on the surface tension of the liquid water-air interface Articles uri icon

authors

  • PEREZ DIAZ, JOSE LUIS
  • ALVAREZ VALENZUELA, MARCO ANTONIO
  • GARCIA PRADA, JUAN CARLOS

publication date

  • September 2012

start page

  • 180

end page

  • 182

issue

  • 1

volume

  • 381

International Standard Serial Number (ISSN)

  • 0021-9797

Electronic International Standard Serial Number (EISSN)

  • 1095-7103

abstract

  • Precise measurements of the surface tension of water in air vs. humidity at 5, 10, 15, and 20 degrees C are shown. For constant temperature, surface tension decreases linearly for increasing humidity in air. These experimental data are in good agreement with a simple model based on Newton's laws here proposed. It is assumed that evaporating molecules of water are ejected from liquid to gas with a mean normal component of the speed of "ejection" greater than zero. A high humidity in the air reduces the net flow of evaporating water molecules lowering the effective surface tension on the drop. Therefore, just steam in air acts as an effective surfactant for the water-air interface. It can partially substitute chemical surfactants helping to reduce their environmental impact.

keywords

  • surface tension; humidity; water-air interface