Title: Water Chemistry
1Water Chemistry Properties of Water
2 Water statistics
(why understanding it is important!)
- Covers 75 of Earths surface
- 97 oceans
- 3 freshwater
- 2 in ice caps and glaciers
- 1 in lakes, underground aquifers, or in
atmosphere - Makes up 70 of the human body
- 92 of blood plasma
- 80 of muscle tissues
- 60 of red blood cells
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4lt 0o C - ice 0o C - 100o C liquid gt
100o C - steam
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7Water is a Polar Molecule -has oppositely
charged ends
- Water consists of an oxygen atom bound to two
hydrogen atoms by two single covalent bonds. - Oxygen has unpaired paired electrons which
gives it a slightly negative charge while
Hydrogen has no unpaired electrons and shares all
others with Oxygen - Leaves molecule with positively and negative
charged ends
8Water molecules form Hydrogen bonds
slightly positive charge
hydrogen bond between () and (-) areas of
different water molecules
slightly negative charge
9Waters Properties
- Cohesion
- Adhesion
- Capillarity
- High Specific Heat
- Latent Heat of Vaporization
- Latent Heat of Melting
- Latent Heat of Sublimation
- Latent Heat of Fusion
- Solid water (ice) is less dense than liquid
- Universal Solvent
- Transparent
10Cohesion
- Water clings to polar molecules through hydrogen
bonding - Cohesion refers to attraction to other water
molecules. - responsible for surface tension
- a measure of the force necessary to stretch or
break the surface of a liquid
11Adhesion
- Adhesion refers to attraction to other
substances. - Water is adhesive to any substance with which it
can form hydrogen bonds.
12Cohesion Adhesion
- For water, adhesion is stronger than cohesion
- Meniscus curve at the surface of a liquid
- If cohesion is stronger than adhesion, meniscus
is convex (like mercury)
Capillary action combo of adhesion cohesion
that shows how water is transported in plants
(ex 200 from roots to needles in a California
sequoia)
13Capillary action
water evaporates from leaves transpiration
adhesion, cohesion and capillary action
water taken up by roots
14- trees have specialized structures to transport
water xylem and phloem plumbing - water molecules are dragged from the roots to
the top of the tree by capillary action and
cohesion hydrogen bonds help water molecules to
each other
15Adaptations of Aquatic Plants/Macrophytes to
Viscosity
- How have aquatic macrophytes have adapted to
emergent life?
16High Specific Heat
- High specific heat
- Amount of heat that must be absorbed or expended
to change the temperature of 1g of a substance 1o
C. - The specific heat of water is 1 calorie/gram C
4.186 joule/gram C which is higher than any
other common substance.
17Impact of waters high specific heat ranges from
the level of the whole environment of Earth to
that of individual organisms.
- A large body of water can absorb a large amount
of heat from the sun in daytime and during the
summer, while warming only a few degrees. - At night and during the winter, the warm water
will warm cooler air. - Therefore, ocean temperatures and coastal land
areas have more stable temperatures than inland
areas. - The water that dominates the composition of
biological organisms moderates changes in
temperature better than if composed of a liquid
with a lower specific heat.
The Earth is over 75 water!
18Latent Heat of Vaporization
- High heat of vaporization
- Amount of energy required to change 1g of liquid
water into a gas (586 calories). - large number of hydrogen bonds broken when heat
energy is applied
19- As a liquid evaporates, the surface of the liquid
that remains behind cools - Evaporative cooling. - Evaporative cooling moderates temperature in
lakes and ponds and prevents terrestrial
organisms from overheating. - Evaporation of water from the leaves of plants or
the skin of animals removes excess heat.
20Thermal Inertia
- High specific heat of water can have large
affects on climate conditions of adjacent air
land masses. - Can you provide any examples?
21Latent Heat
- Latent Heat of Melting amount of heat required
to change ice to liquid water (79.72 cal g-1). - Latent Heat of Evaporation disruption of
hydrogen bonding on evaporation of water (540 cal
g-1). - Latent Heat of Sublimation direct sublimation
of ice to water (679 cal g-1).. - Latent Heat of Fusion fusion of molecules of
0C water to ice (79.72 cal g-1).. - B/C of these properties, large energy inputs are
required to melt ice in the spring, and large
energy losses due to ice cover in winter.
22Universal Solvent
- A liquid that is a completely homogeneous mixture
of two or more substances is called a solution. - A sugar cube in a glass of water will eventually
dissolve to form a uniform mixture of sugar and
water. - The dissolving agent is the solvent and the
substance that is dissolved is the solute. - In our example, water is the solvent and sugar
the solute. - In an aqueous solution, water is the solvent.
- Water is not really a universal solvent, but it
is very versatile because of the polarity of
water molecules.
23- Water is an effective solvent as it can form
hydrogen bonds. - Water clings to polar molecules causing them to
be soluble in water. - Hydrophilic - attracted to water
- Water tends to exclude nonpolar molecules.
- Hydrophobic - repelled by water
24- Water transports molecules dissolved in it
- Blood, a water-based solution, transports
molecules of nutrients and wastes organisms - Nutrients dissolved in water get transported
through plants - Unicellular organisms that live in water absorb
needed dissolved substances
25Solid water (ice) is less dense than liquid
- Ice is less dense than water the molecules are
spread out to their maximum distance - Density mass/volume
same mass but a larger volume
26Oceans and lakes dont freeze solid because ice
floats
- water expands as it solidifies
- water reaches maximum density at
4-degrees C (3.94?C) - water freezes from the top down
- organisms can still live in the water underneath
the ice during winter
27Water is Transparent
- The fact that water is clear allows light to pass
through it - Aquatic plants can receive sunlight
- Light can pass through the eyeball to receptor
cells in the back
28Water Viscosity
- Far greater than viscosity of air inversely
proportional to temp. - Do you think viscosity and buoyancy of water has
helped org. adapt to aquatic environment? Why or
why not?