Demonstration of Capillarity
Capillarity is the action that causes water to rise in narrow tubes. Cap-illarity is made possible by cohesion and adhesion forces. Cohesion is the attraction between molecules of the same substance and adhesion is the at-traction between molecules of different substances. Water molecules in a plant are attracted to each other (cohesion) as well as to the walls of the xylem vessel (adhesion). Xylem vessels have a narrow tube which makes it possible for water to rise in them by capillarity.
To conduct an experiment to demonstrate capillarity.
Plastic tubes of different diametres (the empty ink tube of a pen or a straw can be used), water, GV stain*, clothes pin, and 2 beakers*.
GV will stain clothes and skin.
1. Fill a beaker half way with water and add a few drops of GV to make a coloured solution.
1. Dip the different straws in the coloured solution.
2. Attach 1 clothes pin to the edge of the beaker and tie the other clothes pin to it. In the clothes pin there will be 2 holes. Place 2 straws in the 2 holes.
3. Observe the changes as time goes by.
The coloured solution climbed to a higher level in the thinner tube than the wider one. Xylem vessels in a plant works the same way as a capillary tube.
Collect all the used materials, cleaning and storing items that will be used later. GV stain should be disposed of in the pit latrine.
The narrower the tubes used in this experiment, the more you will be able to see the capillary e ect.
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