water. water is the solvent of life! solute – substance dissolved in a solvent to form a solution...
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WATER
Water is the solvent of Life!Solute – substance dissolved in
a solvent to form a solution Solvent – fluid that dissolves
solutes
Properties of Water
cohesion = water attracted to other water
Molecules because of polar properties
adhesion = water attracted to other materials
Surface tension = water is pulled together creating
the smallest surface area possible
Properties of WaterCapillary Action Because water has both adhesive and
cohesive properties, capillary action is present.
Capillary Action = water’s adhesive property is the cause of capillary action. Water is attracted to some other material and then through cohesion, other water molecules move too as a result of the original adhesion.
Properties of WaterHigh Heat Capacity In order to raise the temperature of
water, the average molecular speed has to increase.
It takes much more energy to raise the temperature of water compared to other solvents because hydrogen bonds hold the water molecules together!
Water has a high heat capacity. “The specific heat is the amount of heat
per unit mass required to raise the temperature by one degree Celsius.”
Properties of WaterDensity Water is less dense as a solid! This
is because the hydrogen bonds are stable in ice – each molecule of water is bound to four of its neighbors.
Solid – water molecules are bonded together – space between fixed
Liquid – water molecules are constantly bonding and rebonding – space is always changing
Properties of Water
Adhesion Cohesion Capillary action High surface tension Holds heat to regulate
temperature (High heat capacity) Less dense as a solid than a liquid
The ocean moderates coastal temperatures Water has high heat capacity, so it
can absorb (or release) large quantities of heat without changing temperature
Moderates coastal temperatures
Salinity
Salinity = total amount of solid material dissolved in water
Can be determined by measuring water conductivity
Typically expressed in parts per thousand (‰)
Constituents of ocean salinity Average seawater salinity = 35‰ Main constituents of ocean
salinity:Chloride (Cl–)Sodium (Na+)Sulfate (SO4
2–)Magnesium (Mg2+)
Processes affecting seawater salinity Processes that decrease seawater
salinity:PrecipitationRunoff Icebergs meltingSea ice melting
Processes that increase seawater salinity:Sea ice formingEvaporation
Surface salinity variation
Pattern of surface salinity: Lowest in high latitudes Highest in the tropics Dips at the Equator Surface processes help explain
pattern
Surface salinity variation
High latitudes have low surface salinity High precipitation and runoff Low evaporation
Tropics have high surface salinity High evaporation Low precipitation
Equator has a dip in surface salinity High precipitation partially offsets high
evaporation
Seawater density
Factors affecting seawater density: Temperature ↑, Density ↓ (inverse
relationship) Salinity ↑, Density ↑ Pressure ↑, Density ↑ Temperature has the greatest
influence on surface seawater density
All freshwater comes from two sources:
Surface Water Lakes, ponds, rivers,
and streams…ALL water above ground
Most urban areas rely on surface water
Supply resources and allow for travel/trade
Ground Water Water that seeps
below ground Some is taken up
and used by plants Large amounts
found in underground rock formations called aquifers
Surface water movement: Water Cycle Earths water supply is constantly recycled
Surface Water Movement
1) Runoff Water flowing down slope along
Earth’s surface or seep into the ground
Run off speed determined by slope of the hill
Ends up in a stream or lake, evaporate, or accumulate into puddles
Movement
Seep into groundGround must have large enough
pores – loose soil Evaporate
Fate of water: Run off or Seep Certain characteristics will
determine whether not water will either seep into or become runoff
1) Vegetation Vegetation allows for loose soil Loose soil allows water to enter ground Gardeners do not pack their soil
Fate of water
2) Rate of precipitation Heavy: Soil clumps together closing pores Fills up ground to quickly and water
becomes runoff Light: Allows water to gently slide through Less erosion
Fate of Water 3) Soil Composition Effects the waters holding capacity Decayed organic matter (humus) Creates the pores in soil – Increases
retain ability Minerals Clay – fine mineral which clump
together Few Spaces Sand – large pores
Fate of Water 4) Slopes Steep: allows for high runoff & little absorption Little: low runoff and high absorption
Formation of Stream systems Runoff Surface water flows in thin sheets and
eventually collects in small channels Runoff increases, channels widen and
become deeper and longer Channels fill up again each time with rain Channel can become a stream
Water sheds: drainage basin Land where all water drains into Divide: High land area that separates watersheds
Stream Load
All the materials that the stream carries
Solution Material that has been dissolved Depends on area where the steam
runs through Erosion of rocks and dirt
Stream Load Suspension
Small particles held up by the turbulence of stream Clay, silt, sand Depends on volume and velocity of water
Bed Load Turbulence of water pushes heavy things Pebbles and cobbles Larger velocity – large objects B/c of abrasion, rocks are smooth
Stream Velocity & Carrying Capacity Discharge = width x depth x velocity
(m) (m) (m/s) As discharge increases so does carrying
capacity
Floods Water fills over the sides of a stream banks Floodplain: broad flat area of land that extends
out from streams for excess flooding
Characteristics of a Freshwater Ecosystem Slow moving waters Low dissolved salt Plant and animal life depends on
depth of water, rate of flow, and amounts of nutrients, sunlight, and oxygen
Include lakes, ponds, rivers, and wetlands
Rivers
START in mountainous regionsColdShallow bedsHighly oxygenated
A river’s characteristics changes with geography, climate, and the runoff from nearby developments
Wetlands
Covered in water at least part of the year
Trap and fix carbon Control flooding and absorb extra
water when other bodies overflow Produce commercial products like
seafood and berries (bogs)
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