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)