Surface Water Tension: Unraveling the Secret of Aquatic Insects!
Seeing this beautiful picture of these two aquatic insects recorded by the photographer Vladimir Ovchinnikov, I remembered a curiosity studied by me that I would like to share with all of you. The initial question to ask is this, "Why do not aquatic insects sink and manage to walk on water?"
The answer and the following my dear friends water is a substance that has numerous interesting physicochemical properties of their own that greatly benefit life, among them adhesion and cohesion, capillarity and surface tension. Surface tension is the force with which the water molecules are attached to each other to form a surface and that surface has a resistance that allows the insects to walk over the water.
The surface tension of the water is the result of the hydrogen bonds, that is to say, it is result of intermolecular forces caused by the attraction of the hydrogens of certain molecules of water with the oxygen of the neighboring water molecules. However, this attraction of the molecules is different inside the liquid, the attraction force of the molecules found on the surface of the water being greater than the attraction force of the molecules below the surface.
The surface tension of the water explains the spherical shape of the water droplets, the fact that some insects are able to stand or "walk" on the water and that some small and light objects do not sink if placed carefully and horizontally .
Image source: Vladimir Ovchinnikov
reference:
- Medeiros RVB, Resende RR. ESTUDANDO A SOLUBILIDADE E A DENSIDADE DE LÍQUIDOS E OBJETOS. Nanocell News. 2015 02/19/2015;2(7). Epub 02/19/2015.2.
- Maia, SRR. et. al. MANUAL DE AULAS PRÁTICAS DE UM LABORATÓRIO DE QUÍMICA COM MATERIAIS ALTERNATIVOS. Subprojeto PIBID/Química/FAEC-UECE, 2013.