8.1 surface tension 1. 1 Some important concepts and phenomena (1) Surface and Interface Surface: The boundary between non-gaseous phases and vacuum The boundary between liquid or solid phase and their vapors can be approximated as Surface In other cases, the boundary is interface So far, we have only considered bulk properties of materials. In this section, the surface interface properties of pure liquid/vapor, solution surface and solid gas interface will be treatedSurface: The boundary between non-gaseous phases and vacuum. The boundary between liquid or solid phase and their vapors can be approximated as Surface. In other cases, the boundary is interface. 1.1 Some important concepts and phenomena (1) Surface and Interface So far, we have only considered bulk properties of materials. In this section, the surface / interface properties of pure liquid/vapor, solution surface and solid / gas interface will be treated. 8.1 surface tension