Science / Chemistry / Viscosity: The resistance a liquid exhibits to flow. Experimentally, the frictional force between two liquid layers moving past each other is proportional to area of the layers and the difference in flow speed between them. The constant of proportionality is called 'viscosity' or 'coefficient of viscosity', and is given the symbol eta. The time required for a liquid to drain out of a capillary tube is directly proportional to its viscosity. The poise is a non-SI unit frequently used to express viscosities.

Lithium (Li)

Science / Periodic Table of Elements / Lithium (Li): Atomic number: 3, Atomic mass: 6.941 g.mol -1, Electronegativity: 1.0, Density: 0.53 -3 at 20 °C, Melting point: 180.5 °C, Boiling point: 1342 °C, Vanderwaals radius: 0.145 nm, Ionic radius: 0 MORE

Helium (He)

Science / Periodic Table of Elements / Helium (He): Atomic number: 2, Atomic mass: 4.00260 g.mol -1, Electronegativity: unknown, Density: 0.178*10 -3 -3 at 20 °C, Melting point: - 272.2 (26 atm) °C, Boiling point: - 268.9 °C, Vanderwaals radius MORE


Science / Tides and Currents / Ekmanspiral : A logarithmic spiral (when projected on a horizontal plane) formed by the heads of current velocity vectors at increasing depths. The current vectors become progressively smaller with depth. They spir MORE