In this paper, a qualitative explanation of the causes of surface tension forces at a liquid–gas interface acting parallel to an interface is presented. None of the common explanations of surface tension given in preliminary physics courses consider the reasons behind the attractive forces between nearest neighbor molecules acting parallel to a surface. The earlier proposed explanations are based on the assumption that there is a concentration gradient at the liquid–gas interface. The analysis is based on considering the anisotropic pressure tensor in the interface layer. Unfortunately, these explanations are difficult to understand in preliminary physics courses. Additionally, they do not pay enough attention to the physical reasons for the formation of a special surface layer with the distance between the nearest neighbors in the direction parallel to the surface greater than in the direction normal to it. In this paper, a simple qualitative explanation of surface tension forces at a liquid–gas interface is provided. The consideration includes the reasons for the formation of a special liquid–gas interface and the reasons for the appearance of tangent surface tension forces. The instability of the liquid–gas interface and the associated fluctuations are also discussed.

在本文中，对平行于界面作用的液-气界面处的表面张力的原因进行了定性解释。在初级物理课程中给出的表面张力的常见解释都没有考虑到与表面平行的最近邻分子之间的吸引力背后的原因。早先提出的解释是基于在液-气界面存在浓度梯度的假设。该分析基于考虑界面层中的各向异性压力张量。不幸的是，这些解释在初级物理课程中很难理解。此外，他们没有足够注意形成特殊表面层的物理原因，在平行于表面的方向上最近邻之间的距离大于在垂直方向上的距离。在本文中，提供了液气界面表面张力的简单定性解释。考虑包括形成特殊液-气界面的原因和出现切线表面张力的原因。还讨论了液-气界面的不稳定性和相关的波动。考虑包括形成特殊液-气界面的原因和出现切线表面张力的原因。还讨论了液-气界面的不稳定性和相关的波动。考虑包括形成特殊液-气界面的原因和出现切线表面张力的原因。还讨论了液-气界面的不稳定性和相关的波动。