When a capillary tub eis dipped into a liquid, the capilary ridse is h
Answers
Capillary action (or capillarity) describes the ability of a liquid to flow against gravity in a narrow space such as a thin tube.
This spontaneous rising of a liquid is the outcome of two opposing forces:
Cohesion – the attractive forces between similar molecules or atoms, in our case the molecules or atoms of the liquid. Water, for example, is characterized by high cohesion since each water molecule can form four hydrogen bonds with neighboring molecules.
Adhesion – the attractive forces between dissimilar molecules or atoms, in our case the contact area between the particles of the liquid and the particles forming the tube.
The capillarity of the liquid is said to be high when adhesion is greater than cohesion, and vice versa. Hence, knowledge of the liquid is not sufficient to determine when capillary action will occur, since we must also know the chemical composition of the tube. These two, together with the contact area (the tube's diameter), comprise the key variables. For example, water in a thin glass tube has strong adhesive forces due to the hydrogen bonds that form between the water molecules and the oxygen atoms in the tube wall (glass = silica = SiO2). In contrast, mercury is characterized by stronger cohesion, and hence its capillarity is much lower.
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