SCIENCE 8 Unit 1- Water Systems on Earth

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SCIENCE 8Unit 1- Water Systems on Earth

• Slideshow 2
• Chapter 1 -The water cycle plays a
• vital role on Earth
• Section 1.2 How Ocean Water Differsfrom Fresh
  Water

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Review -Remember These.
Lithosphere - Consists of the solid earth crust
Atmosphere - The layer of air and gases
surrounding the Earth
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More Vocab
Hydrosphere -Consists of all the water found on
the planet including that which is found on the
Lithosphere and in the Atmosphere
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1.2 How Ocean Water Differsfrom Fresh Water

• When distinguishing between ocean water and
  fresh water, one should consider
• salinity
• density
• freezing point

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1.2 How Ocean Water Differsfrom Fresh Water
(Salinity)

• The amount of salt dissolved in a specific amount
  of water is called salinity.
• Ocean waters salinity 200X greater than fresh
  water
• Average salinity of oceans is 35 parts per
  thousand
• This is the same as if you mixed 35 g of salt in
  1 L of water.
• Note
• Oceans at equator (evaporation) and poles (ice)
  have the highest salinity (removing water
  increases salinity)
• Ocean locations near rivers have low salinity,
  due to addition of fresh water

See page 368 - 370
from the World Ocean Atlas 2001
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1.2 How Ocean Water Differsfrom Fresh Water
(Salinity) continued....
From the diagram on the left where is salinity
the highest? Lowest?
Suggest a reason for the salinity differences.
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Composition of Salt Water

• Salt water is composed of minerals dissolved in
  rainwater during run-offs from the land occurring
  over millions of years
• Volcanic eruptions also
• release minerals from
  inside Earth

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Density of Salt Water

• Density is the amount of mass of a substance in a
  certain unit volume.
• If the same volume of a substance ie water has
  more mass it likely has a higher density.
• Density how tightly packed the molecules are in
  an object
• dense matter sinks below less dense matter
• Explain why we float better in salt water
• than fresh water.
• What does this tell you about the density of
• Salt water compared to fresh?

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Density of salt water continued

• Question Time?????
• When river water meets the ocean at the rivers
  mouth the water doesnt mix together
  immediately. Based upon your knowledge of density
  describe what likely happens to the two water
  sources initially.

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Freezing Point

• Salt water has slightly different properties
  than fresh water
• Fresh water freezes at 0 ºC
• Salt water freezes at 1.9 ºC
• What do you think might account for the
  difference in freezing point?