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Water on Earth

S8.D.1.3.1-4

Unit 4

Lesson 3

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Water Cycle

When water evaporates from a plant

Why clouds float?

3

Water cy

cle for ki

ds

The Sun powers the Water cycle

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Watershed

• An area of land that drains rain or snow into a particular body of water

• An area of land that water flows over to reach a river is the river’s watershed

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Chesapeake Bay Watershed

• We live in both the Susquehanna River and Chesapeake Bay watersheds

• About 150 different rivers and streams flow into Chesapeake Bay

• In the bay, fresh water from rivers mixes with saltwater from oceans

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Pollution in Watersheds

• Pollution anywhere in a watershed can lead to pollution in a body of water

• Runoff can wash soil, fertilizers, litter, toxic chemicals, and other pollutants into creeks rivers bay ocean

Farmers often add nutrients to soil to help crops grow

• Nutrients can make their way to a body of water and cause an overgrowth of algae (Algal Bloom)

• Algae depletes the water of oxygen that other organisms need to live

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Freshwater Bodies

Lotic Systems–Creeks, streams, and rivers–Water is moving from high elevation to lower elevation–Flow rate or current rate at which water flows– Organisms have adaptations to prevent them from being swept downstream

Lentic Systems–Water is still or almost still–Lake, wetlands

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Changes to Lentic Systems

– Changes in flow rate, temperature ,and water quality can affect a river’s/stream’s Biodiversity (variety of organisms that can live there)

• Heavy rainfall can increase flow rate

• Power plants use river water for cooling

• Litter and pollutants can move into a stream from the watershed

Bill Nye- Rivers and Streams

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Wetlands• Marshes, swamps, bogs

• An area of land that is underwater for all or part of the year

• Form when water washes over land from rivers, creeks, streams, and lakes

•Filter pollutants, excess nutrients, and sediments out of the water that moves through them

•Improve quality of water that flows to other bodies of water downstream

Link

How they Help?

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Saltwater Bodies

• Oceans cover 70% of Earth

• Estuary- the wide part of a river where it nears the sea; fresh and

salt water mix • Bay- body of water that

connects to an ocean

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Saltwater vs Freshwater

Salinity• Is the dissolved salt content (NaCl) in water• Measured in ppm (parts per million)

– Oceans have a salinity of 35,000 ppm (35 ppt)– Freshwater has a salinity of about 500 ppm

Why are oceans salty?

Wiki

seawater

Why are

some lakes

salty?

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Saltwater vs Freshwater

Density• Saltwater is denser than freshwater

• density of saltwater is 1.025g/ml

•Pure water will not conduct electricity•Freshwater is a poor conductor of electricity (has few dissolved ions)•Saltwater is a good conductor of electricity

–When salt dissolves in water Na(+) ions and Cl(-) ions form

Conductivity

Saltwater

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Saltwater vs Freshwater

Freezing and Boiling point• Salt lowers the freezing point and higher the

boiling point• For every 29.2g of salt per liter of water (kg), the

freezing point lowers by 3.3 F• Freshwater freezes at 32 F……..Seawater freezes at ~28 F

• For every 29.2g of salt per liter of water (kg), the boiling point raises 0.9 F

• Freshwater boils at 212 F……..Seawater boils at ~213F

The above numbers assume seawater’s salinity is 35 ppt.The salinity of seawater is not constant everywhere