http://www.ck12.org Chapter 15. Water
FIGURE 15.7
Ice fishing, a popular winter activity, would
not be possible without the unusually low
density of solid water, because ice would
sink and lakes would freeze solid.Surface Tension
Surface tension was discussed in the chapter,States of Matter. Water has a high surface tension because of its strong
intermolecular hydrogen bonds. Surface tension can be seen by the curved meniscus that forms when water is in a
thin column, such as a graduated cylinder or a buret (Figure15.8).
FIGURE 15.8
The meniscus of water in a graduated
cylinder (left) forms because of water’s
hydrogen bonding. The diagram on the
right shows the correct way to use a grad-
uated cylinder to measure the volume of
a liquid.Vapor Pressure
The hydrogen bonding between liquid water molecules also explains water’s unusually low vapor pressure for a
molecule of its size. Relatively few molecules of water are capable of escaping the surface of the liquid and entering
the vapor phase. Because evaporation is slow, the resulting vapor exerts a low pressure in a closed container. Low
vapor pressure is an important physical property of water that prevents lakes, oceans, and other large bodies of water
from evaporating at a much faster rate.