A liquid has two properties (amongst many) called cohesion and adhesion. Cohesion is the force of attraction between molecules/atoms of the liquid itself. Adhesion is the force of attraction between the molecules/atoms of the liquid and other substances. Therefore, if the molecules' attraction for another substance is greater than the attraction between the molecules, the molecules will preferentially interact with the other substance. When you have a substance that is more attracted to the walls of a capillary tube than itself (i.e. adhesion > cohesion), the substance will exhibit capillary action and form a concave meniscus. Mercury, however, has a stronger cohesive force between its atoms than adhesive force to the walls of a capillary tube, and therefore will not preferentially interact with the tube, thus not demonstrating capillary action and forming a convex meniscus. Curved surfaces have a higher pressure (called LaPlace pressure) on the concave side of the curve than on the convex side. Because mercury has a convex meniscus it has a lower LaPlace pressure in the capillary than the surrrounding liquid. It will therefore show a capillary drop rather than the more common capillary rise seen with materials that have a concave meniscus like water.
That is capillary attraction.
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There are primarily three types of capillary tubes: open capillary tubes, closed capillary tubes, and capillary tubes with a tapered end. Open capillary tubes are used in applications such as blood sampling, while closed capillary tubes are often employed in thermometers or pressure measurement. Tapered capillary tubes facilitate fluid movement and can enhance the flow rate. Each type serves specific functions based on the requirements of the application.
Mercury is more dense than water.
Capillary tubes are renowned for their capillary action on liquids, i.e. they cause liquids to rise up inside them. Capillary tubes are the essence of thermometers that use a liquid indicator. In biology and the plant world, capillary tubes are fundamental to the movement of fluids through the systems of living organisms.
Capillary rise is influenced by the diameter of the capillary tube; specifically, narrower tubes exhibit a greater height of liquid rise due to stronger adhesive forces between the liquid and the tube walls relative to the cohesive forces within the liquid. This phenomenon is described by the capillary action equation, where the height of rise is inversely proportional to the diameter of the tube—smaller diameters lead to higher capillary rise. As the diameter increases, the height of the liquid column decreases, demonstrating the strong relationship between tube size and capillary action.
capillarity, also known as capillary action.
thermometer consisting of mercury contained in a bulb at the bottom of a graduated sealed glass capillary tube marked in degrees Celsius or Fahrenheit; mercury expands with a rise in temperature causing a thin thread of mercury to rise in the tube
Mercury falls in a capillary tube due to the combination of capillary action and gravity. Capillary action is the tendency of a liquid to be drawn up into a narrow tube against the force of gravity. When the adhesive forces between the mercury and the walls of the capillary tube are greater than the cohesive forces within the mercury, the mercury will move downward in the tube.
Liquid rises in and out of cappilarry to compansate pressure difference. Rise of a liquid in capillary is indirectly proportional to radius of tube so liquid goes higher in a narrow tube.
This happens due to the difference in adhesive and cohesive forces. Water molecules are more attracted to the walls of the tube (adhesive forces) than to each other (cohesive forces), causing water to rise. Mercury has stronger cohesive forces compared to adhesive forces, so mercury is more attracted to itself than to the walls of the tube, causing it to be depressed or fall in the capillary tube.
Capillary motion is a movement of liquids in small tubes. This motion can be also ascensional.