Properties of Water - Freshwater Ecology: Concepts and Environmental Applications - page 13

2 Properties of Water
Chemical and Physical Properties
Relationships among Water Viscosity, Inertia, and Physical Parameters
Movement of Water
Forces That Move Water
Summary
Questions for Thought
Unique physical properties dictate how water acts as a solvent and
how its density responds to temperature. These physical properties have
strong biological implications and knowledge of water's characteristics
forms the foundation for aquatic science. The physical properties of water
are so central to science that they form the basis of several systems of mea-
surement, including mass, heat, viscosity, temperature, and conductivity.
The properties of water influence how it changes geomorphology, conveys
human waste, links terrestrial and aquatic habitats, and constrains evolu-
tion of organisms. In this chapter I explore how viscosity and inertia of
water vary with scale, temperature, and relative velocity related to aquatic
ecology. Movement of water is discussed in the last section, including how
flowing water interacts with solid surfaces.
CHEMICAL AND PHYSICAL PROPERTIES
One of the many unusual properties of water is that it exists in liquid
form at the normal atmospheric temperatures and pressures encountered
on the surface of Earth (Table 2.1). The majority of common compounds
or elements take the form of gas or solid in our biosphere (exceptions in-
clude mercury and numerous organic compounds). The range of tempera-
tures and pressures at which water occurs in a liquid state and additional
distinguishing characteristics are related to polarity of the molecule and hy-
drogen bonding. The oxygen atom attracts electrons so the probability is
13