Properties of Water
Water content of selected organism and foods
% of mass % of mass
Marine
invertebrates 97 Broccoli 90
Human fetus
(1 month) 93 Milk 88
Fish 82 Apples 85
Human adult 70 Grapes 80
Eggs 75
Distribution of Water on the Earth
Only a small percentage (<3%) of water on Earth is fresh water.
Lakes and rivers account for just 0ver 0.1% of the earth’s total water
Global water use (1900-2000)
Hydrologic cycle
Evaporation
Transpiration
Condensation
Precipitation
Processes that
cycle water
between air and
earth surface
Evaporation and transpiration
Transpiration is a process in which water escapes through the pores
on leaf surfaces.
Composition of natural waters
? Fresh water,dissolved solids <0.1%.
– Drinking water standard,dissolved solids <0.05%
– Major constituents,Ca2+,Mg2+,HCO3-.
? Sea water,dissolved solids ~3.5% (Dead sea,25%)
– Major constituents
Cl- 19,000 ppm Na+ 10,600 ppm
SO42- 2,600 ppm Mg2+ 1,300 ppm
HCO3- 140 ppm Ca2+ 400 ppm
Br- 65 ppm K+ 380 ppm
Water as solvent and as ecosystem
? Water is a remarkable solvent,
– dissolves and transports a wide range of materials.
– Interacts with soil and particles and gases in the air
? Water houses ecosystems.
– A large percentage of the biosphere lives in some
form of aqueous environment.
– Water quality is often defined in terms of the ability
of the aqueous environment to support the normal
range of biological species.
Water molecule and hydrogen bonding
H-bonds have a profound effect on the physical properties
of water in both its liquid and solid states.
Boiling point and melting point
Without H-bonds,water would be a gas at the temperature
found on earth,and our form of life and environment would
not be possible.
Heat capacity
? Heat capacity is the amount of heat required to raise the
temperature of a given mass by 1oC,Unit,cal/oC/g
? Water has the highest heat capacity of any common
liquid or solid.
– H2O,Cp =1 cal/oC/g
– Alcohol,0.535 cal/oC/g
– Acetone,0.506 cal/oC/g
– Sulfuric acid,0.411 cal/oC/g
– Benzene,0.389 cal/oC/g
– Carbon tetrachloride,0.198 cal/oC/g
– Mercury,0.03346 cal/oC/g
Heat capacity,Implication
? The same amount of heat absorbed or released by
water causes smaller temperature change than other
substances.
? The oceans absorb heat from the sun in summer,and
release it in the winter without causing dramatic
temperature change,
? Without water absorbing and releasing heat,daily and
season temperatures on the earth would fluctuate as
drastically as they do on the waterless moon and the
planet Mercury,(where T fluctuates by hundreds of
degrees during the light-dark cycle).
? Stabilize temperatures of organisms
Why coastal cities have mild climate?
Heat of fusion and vaporization
? Heat of fusion,the amount of heat required to convert 1g
of solid to a liquid at its melting point.
? Heat of vaporization,the amount of heat required to
convert 1g of a liquid to a vapor at its boiling point.
? H-bonds make the heat of fusion and heat of vaporization
for water higher than for practically any other substances.
? In summer,water evaporates from the surfaces of oceans
and takes heat energy from the surrounding land,? the
nearby land mass is cooled.
? In winter,water vapor condenses and releases heat to
the surrounding ? temperature of the surrounding air is
raised,
Temperature-density relationship
? Water has the maximum density at 4oC
? That’s why ice floats on the water surface,reducing
heat loss from the water under the ice.
? If water trapped in cracks in rocks freezes,the force
of expansion would split the rock,an important
process in the weathering of rock.
Summary,Important properties of water
Property Effects and significance
Excellent solvent Transport nutrients and waste products,
making biological processes possible in an
aqueous medium
Maximum density at 4oC Ice floats
Higher heat of
vaporization than any
other material
Determines transfer of heat and water
between the atmosphere and bodies of water
Higher heat of fusion
than any other liquid
except ammonium
Temperature stabilized at the freezing point
of water
Higher heat capacity
than any other liquid
except ammonia
Stabilization of temperatures of organisms
and geographical regions
Transparent to visible
and longer-wavelength
fraction of UV light
Allow light required for photosynthesis to
reach considerable depth in bodies of water
Study questions
1,On a global scale,what type of water use in human
society demands most water?
2,What are the major processes transporting water
between air and earth surface?
3,Summarize the important physical properties of
water and their significances to the environment.
Water content of selected organism and foods
% of mass % of mass
Marine
invertebrates 97 Broccoli 90
Human fetus
(1 month) 93 Milk 88
Fish 82 Apples 85
Human adult 70 Grapes 80
Eggs 75
Distribution of Water on the Earth
Only a small percentage (<3%) of water on Earth is fresh water.
Lakes and rivers account for just 0ver 0.1% of the earth’s total water
Global water use (1900-2000)
Hydrologic cycle
Evaporation
Transpiration
Condensation
Precipitation
Processes that
cycle water
between air and
earth surface
Evaporation and transpiration
Transpiration is a process in which water escapes through the pores
on leaf surfaces.
Composition of natural waters
? Fresh water,dissolved solids <0.1%.
– Drinking water standard,dissolved solids <0.05%
– Major constituents,Ca2+,Mg2+,HCO3-.
? Sea water,dissolved solids ~3.5% (Dead sea,25%)
– Major constituents
Cl- 19,000 ppm Na+ 10,600 ppm
SO42- 2,600 ppm Mg2+ 1,300 ppm
HCO3- 140 ppm Ca2+ 400 ppm
Br- 65 ppm K+ 380 ppm
Water as solvent and as ecosystem
? Water is a remarkable solvent,
– dissolves and transports a wide range of materials.
– Interacts with soil and particles and gases in the air
? Water houses ecosystems.
– A large percentage of the biosphere lives in some
form of aqueous environment.
– Water quality is often defined in terms of the ability
of the aqueous environment to support the normal
range of biological species.
Water molecule and hydrogen bonding
H-bonds have a profound effect on the physical properties
of water in both its liquid and solid states.
Boiling point and melting point
Without H-bonds,water would be a gas at the temperature
found on earth,and our form of life and environment would
not be possible.
Heat capacity
? Heat capacity is the amount of heat required to raise the
temperature of a given mass by 1oC,Unit,cal/oC/g
? Water has the highest heat capacity of any common
liquid or solid.
– H2O,Cp =1 cal/oC/g
– Alcohol,0.535 cal/oC/g
– Acetone,0.506 cal/oC/g
– Sulfuric acid,0.411 cal/oC/g
– Benzene,0.389 cal/oC/g
– Carbon tetrachloride,0.198 cal/oC/g
– Mercury,0.03346 cal/oC/g
Heat capacity,Implication
? The same amount of heat absorbed or released by
water causes smaller temperature change than other
substances.
? The oceans absorb heat from the sun in summer,and
release it in the winter without causing dramatic
temperature change,
? Without water absorbing and releasing heat,daily and
season temperatures on the earth would fluctuate as
drastically as they do on the waterless moon and the
planet Mercury,(where T fluctuates by hundreds of
degrees during the light-dark cycle).
? Stabilize temperatures of organisms
Why coastal cities have mild climate?
Heat of fusion and vaporization
? Heat of fusion,the amount of heat required to convert 1g
of solid to a liquid at its melting point.
? Heat of vaporization,the amount of heat required to
convert 1g of a liquid to a vapor at its boiling point.
? H-bonds make the heat of fusion and heat of vaporization
for water higher than for practically any other substances.
? In summer,water evaporates from the surfaces of oceans
and takes heat energy from the surrounding land,? the
nearby land mass is cooled.
? In winter,water vapor condenses and releases heat to
the surrounding ? temperature of the surrounding air is
raised,
Temperature-density relationship
? Water has the maximum density at 4oC
? That’s why ice floats on the water surface,reducing
heat loss from the water under the ice.
? If water trapped in cracks in rocks freezes,the force
of expansion would split the rock,an important
process in the weathering of rock.
Summary,Important properties of water
Property Effects and significance
Excellent solvent Transport nutrients and waste products,
making biological processes possible in an
aqueous medium
Maximum density at 4oC Ice floats
Higher heat of
vaporization than any
other material
Determines transfer of heat and water
between the atmosphere and bodies of water
Higher heat of fusion
than any other liquid
except ammonium
Temperature stabilized at the freezing point
of water
Higher heat capacity
than any other liquid
except ammonia
Stabilization of temperatures of organisms
and geographical regions
Transparent to visible
and longer-wavelength
fraction of UV light
Allow light required for photosynthesis to
reach considerable depth in bodies of water
Study questions
1,On a global scale,what type of water use in human
society demands most water?
2,What are the major processes transporting water
between air and earth surface?
3,Summarize the important physical properties of
water and their significances to the environment.
