Answer :
Final answer:
The rise or fall of water and mercury in a capillary tube is determined by the interplay of surface tension, liquid density, and tube radius. Water rises due to its adhesive forces with glass, while mercury falls due to stronger cohesive forces. Calculations of the exact rise or fall can be made with knowledge of the liquid's properties and the tube's dimensions.
Explanation:
The height to which water or mercury rises or falls in a capillary tube is influenced by several key factors: the liquid's surface tension, the density of the liquid, and the radius of the tube. For water, which exhibits high adhesive forces, it tends to rise in a glass capillary tube.
In contrast, mercury, which has stronger cohesive forces than adhesive forces with glass, falls in the same capillary tube. This difference in behavior is due to the relative strengths of adhesive forces (liquid to glass) versus cohesive forces (liquid to liquid).
At a temperature of 25 °C, the specific phenomenon of capillary action can be quantified using the formula for capillary rise, which takes into account the liquid's surface tension (τ), the density (ρ), gravity (g), and the tube's radius (r). The formula is given by h = (2τ / (ρgr)), where h represents the height to which the liquid rises.
For instance, if we have a capillary tube with a certain diameter and know the surface tension and density of water, we can calculate how high water will rise in that tube. Conversely, applying the same formula to mercury, acknowledging its surface tension and higher density, will give us the distance it falls in the capillary tube. This illustrates the importance of material properties and tube dimensions in capillary action.
