let's learn about surface tension surface tension is a force that can be produced by water molecules this coin doesn't sink because it is held up by surface tension water forms a domed or droplet shape due to surface tension water molecules produce surface tension water mole ules have a slight negative charge on one side and a slight positive charge on the other water molecules are polar because of these charges weak bonds can form between water molecules these weak bonds are called polar calent bonds and are characterized by a partial sharing of electrons surface tension plays a role in the respiratory system the tiny Alvis is the part of the lung that exchanges oxygen and carbon dioxide with the blood the spherical alvioli form clusters the Alvi are also lined with mucus the curved surface of the Alvi produce surface tension let's look at this in a little bit of detail lass's law describes the relationship between the gas pressure needed to balance the surface tension and the radius of a curved surface such as a sphere the gas pressure must balance the collapsing force of the surface tension the small radius of the Alvis results in a large balancing pressure the large Pressure Works to collapse the Alvis however in a healthy lung the Alvis does not collapse because of a substance called surfactant that is secreted by type 2 cells lining the alvas surfactant Works to reduce surface tension as long as the surfactant secreting cells are healthy the alvioli remains inflated and do not collapse we hope you have learned something about surface tension and see you next time