Of state. Contents and Concepts 1. Comparison of Gases, Liquids, and Solids Changes of State

FIGURE 11.19

Liquid levels in capillaries

(A) Capillary rise, due to the attraction of water and glass. Hydrogen bonds between the water molecules and the gas are illustrated. The final water level in the capillary is a balance between the force of gravity and the surface tension of water. (B) Depression, or lowering, of mercury level in a glass capillary. Unlike water, mercury is not attracted to glass.
436 11 States of Matter; Liquids and Solids

▼surface area of this film, the water level begins to rise also. The final water level is a balance between the surface tension and the potential energy required to lift the water against gravity. Note that the meniscus, or liquid surface within the tube, has its edges curved upward; that is, it has a concave shape. In the case of mercury, the liquid level in the capillary is lower than for the liquid outside (Figure 11.19B). Also, the meniscus has its edges curved downward; that is, it has a convex shape. The difference between Figures 11.19A and 11.19B results from the fact that the attraction between mercury atoms is greater than the attraction of mercury atoms for glass, in contrast to the situation for water and glass.