Cohesive forces between molecules cause the surface of a liquid to contract to the smallest possible surface area. This general effect is called surface tension. Explain the phenomena of surface tension and capillary action Key Points. Attractive forces between molecules of the same type are called cohesive forces. Surface tension arises from the strong interactions between water molecules, explain phenomena such as meniscus, surface tension and capillary action.
A shown on Left -- a concave meniscus occurs when the particles of the liquid are more strongly attracted to the container than to each other, causing the liquid to climb the walls of the container. This occurs between water and glass. B shown on Right -- a convex meniscus occurs when the particles in the liquid have a stronger attraction to each other than to the material of the container.
Convex menisci occur, for example, between mercury and glass in barometers.
Capillary action - Wikipedia
Cohesive attraction or cohesive force is the action or property of similar molecules sticking together, being mutually attractive. Cohesion, along with adhesion attraction between unlike moleculeshelps explain phenomena such as meniscus, surface tension and capillary action. Examples of surface tension in action include the following: Surface tension has the dimension of force per unit length, or of energy per unit area. The two are equivalent—but when referring to energy per unit of area, people use the term surface energy—which is a more general term in the sense that it applies also to solids and not just liquids.
11.4: Intermolecular Forces in Action: Surface Tension, Viscosity, and Capillary Action
Its SI unit is newton per meter. In terms of energy: Thus, surface tension can be also measured in the SI system as joules per square meter. Since mechanical systems try to find a state of minimum potential energy, a free droplet of liquid water will try to assume a spherical shape, which has the minimum surface area for a given volume. Adhesion of water to the surface of a material will cause an upward force on the liquid. The surface tension acts to hold the surface intact.
Capillary action occurs when the adhesion to the surface material is stronger than the cohesive forces between the water molecules. The height to which capillary action will take water is limited by surface tension and gravity. Because they affect the surface properties of a liquid, soaps and detergents are called surface-active agents, or surfactants.
The surfactants reduce the surface tension of water below that of fuel, so the fluorinated solution is able to spread across the burning surface and extinguish the fire. Such foams are now used universally to fight large-scale fires of organic liquids. The Phenomenon of Capillary Action. Capillary action seen as water climbs to different levels in glass tubes of different diameters.
When a glass capillary is is placed in liquid water, water rises up into the capillary.
The height to which the water rises depends on the diameter of the tube and the temperature of the water but not on the angle at which the tube enters the water. The smaller the diameter, the higher the liquid rises. Cohesive forces bind molecules of the same type together Adhesive forces bind a substance to a surface The same phenomenon holds molecules together at the surface of a bulk sample of water, almost as if they formed a skin.
When filling a glass with water, the glass can be overfilled so that the level of the liquid actually extends Capillary action is the net result of two opposing sets of forces: Water has both strong adhesion to glass, which contains polar SiOH groups, and strong intermolecular cohesion. When a glass capillary is put into water, the surface tension due to cohesive forces constricts the surface area of water within the tube, while adhesion between the water and the glass creates an upward force that maximizes the amount of glass surface in contact with the water.
Surace Tension and Capillary Action
If the adhesive forces are stronger than the cohesive forces, as is the case for water, then the liquid in the capillary rises to the level where the downward force of gravity exactly balances this upward force. The upper surface of a liquid in a tube is called the meniscus, and the shape of the meniscus depends on the relative strengths of the cohesive and adhesive forces.
Capillary action of water compared to mercury, in each case with respect to a polar surface such as glass.
Differences in the relative strengths of cohesive and adhesive forces result in different meniscus shapes for mercury left and water right in glass tubes.
Mark Ott Polar substances are drawn up a glass capillary and generally have a concave meniscus. Fluids and nutrients are transported up the stems of plants or the trunks of trees by capillary action. Plants contain tiny rigid tubes composed of cellulose, to which water has strong adhesion.Capillarity and Surface Tension - Surface Tension - Physics
Jules Renouard et cie. Joseph and Edward Parker,volume 10, pp. John Uri Lloyd "References to capillarity to the end of the year ," Archived at the Wayback Machine. On pages 91—92, he quotes from this book: He proposed that mosquitoes, butterflies, and bees feed via capillary action, and that sap ascends in plants via capillary action.
Vincenzo Giuntini,pp. Archived at the Wayback Machine. Hall,pp. Robert Hooke An attempt for the explication of the Phenomena observable in an experiment published by the Right Hon. Robert Boyle, in the 35th experiment of his Epistolical Discourse touching the Air, in confirmation of a former conjecture made by R.
- Capillary action
Hooke's An attempt for the explication James Allestry,pp.