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Hydrosphere Review

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Hydrosphere Review

  1. 1. Hydrosphere Review Water's Special Properties & The Water Cycle
  2. 2. Chemical Formula • H2O • Shows how many and which type of atoms make a single molecule O H H • How many atoms form one water molecule? Chemical bond
  3. 3. Polarity • Oxygen hogs the electrons • Hydrogen atoms don't get their fair share of "shared electron time" • Water is a polar molecule – O end of molecule = slight negative charge – H end = slightly positive • NOT an ion (no net charge)
  4. 4. Hydrogen Bonding • Attraction between oppositely charged regions of water molecules • Each molecule can have H-bonds with four other water molecules • Weak bonds continually break & reform
  5. 5. Frozen Water's Density • • • • Water freezes at 0° C (32o F) H2O is most dense at 4° C (as a liquid) Crystal lattice formation the result of water's polarity Density of solid H2O is 9% less than liquid H2O
  6. 6. Cohesion • Attraction between particles of the same substance (i.e. water molecules) • Results in Surface Tension – molecules at the surface cling together – produces a "film" on top of water that allow some things to remain afloat – only at surface
  7. 7. Adhesion • Attraction between particles of different substances – i.e. water and glass • Explains capillary action – water molecules will “tow” each other along when in a thin tube • Transports water against gravity (roots to leaves) in plants
  8. 8. Water Resists Temperature Changes • Heat = how fast molecules are moving • Water's polarity makes the molecules both "sticky" and "slippery" (like magnets that attract & repel) – stickiness: resistant to vaporizing because of cohesion – slipperiness: resistant to freezing because they keep sliding around • Specific Heat = energy needed to raise or lower 1g of anything by 1° C – Water has a very high specific heat • Water stabilizes air temperatures – Absorbs/releases large amounts of heat with only a slight change in its own temperature
  9. 9. Water Vapor • Water boils at 100°C (212oF) – LOTS of energy to break hydrogen bonds • Evaporation can occur at much lower temperatures • Water vapor in atmosphere resists temperature changes • Evaporation absorbs lots of heat energy – Evaporative cooling (sweat, panting, seashore)
  10. 10. Water Cycle Overview
  11. 11. Transpiration • Emission of water vapor from plants – Plants absorb water from soil to use in photosynthesis – Water vapor released through stomata (pores) under leaves
  12. 12. Precipitation • Water falling from the atmosphere – Vapor molecules collide & join to form droplets – Falls as rain, snow, sleet, or hail
  13. 13. Infiltration • Water absorbed into subsurface of dirt & rocks – Water percolates down between spaces in soil – Groundwater empties into streams/rivers/oceans or is stored underground in aquifers • Saturation = all the spaces in soil & rock are filled with water – Flooding occurs: • when soil becomes saturated, or • when precipitation falls faster than infiltration can occur
  14. 14. Groundwater • Precipitation seeps down through soil & rock • Layers act as filters that trap contaminants • Water table: imaginary line between the waterlogged soil and the soil not saturated with water – varies with seasonal precipitation, pumping, & geography • Two types of aquifers: – unconfined: water supply which has a solid layer of rock under it, but a permeable layer of rocks above it – confined: water supply sandwiched between two solid rock layers through which water cannot pass • pressure builds up and can form an artesian well
  15. 15. Surface Runoff • Water flows over the ground instead of sinking into the ground – Snow melts, rain runs off surfaces, etc. – Streams and rivers carry water back to oceans
  16. 16. Earth's Water Distribution • • • • • 97% in oceans (salt water) 2% trapped in glaciers, icebergs and polar ice caps .7% groundwater and soil moisture .01 % surface fresh water (lakes, rivers, wetlands) .001% atmospheric moisture (rain, dew, water vapor)
  17. 17. Salinity • A measure of the dissolved salt in water – 35 g of salt per kg of ocean water – concentration of salt varies with location • Water dissolves salts & minerals from the soil as it passes over/through the ground – lakes & rivers: have salts too, but are carried away with the water in the hydrologic cycle – Great Salt Lake has no outlet • water only leaves through evaporation
  18. 18. Glaciers • Years of continual snows compress layers below – Firn (hard-packed ice) – Polar or high-altitude areas • Thick layers get heavy/dense • Insulated bottom layer melts – Valley glaciers move down mountainsides – Continental glaciers (ice caps & ice sheets) flow outward in all directions from a central point – Typically move 1 - 3 meters each day
  19. 19. Flowing Ice • Valley (alpine) glaciers carve valleys by scouring mountainsides • Pick up, carry & deposit rocks • Crevasses form when glaciers move quickly (up to 30 m/day) • Retreat: melting occurs faster than snow accumulates
  20. 20. animation
  21. 21. Continental Glacier Ice Shelf Calving • Temperatures remain freezing across continent, even to sea level • Calving occurs as big chunks of the glacier fall off into the ocean to become icebergs
  22. 22. Icebergs • Glaciers reaching seas/lakes float on top – Ice Shelf = portion of connected glacier floating on water (may be miles wide/long) – Large chunks break away into icebergs – 90% of iceberg remains below water surface
  23. 23. GROUNDWATER & SOIL MOISTURE - .7% of Earth's Water • 95% of the water humans use • Gravity pulls water down – deeper underground – out to rivers/lakes/oceans
  24. 24. WATER POLLUTION • Open dumping of waste/litter – industrial legislation has helped • Groundwater contamination: – pesticides & fertilizers – gasoline (storage tanks, oil spills ) – landfills (mercury, human waste, battery acid) – hard to test/monitor sources •Thermal water pollution – flooding/natural disasters –water for cooling machinery raises temperatures when discharged back into lakes/rivers –upsets balance of entire ecosystem
  25. 25. Humidity • Absolute humidity: tells the amount of moisture in the air – warm air holds more water vapor than cool air - why? – example: absolute humidity of 8.7 mg/L at 20 oC • Relative humidity - tells how much water the air is holding compared to the most it could hold at a certain temperature – 50% humidity means the air is holding half of the moisture it is able to hold at that temperature 8.7
  26. 26. Dew • Ground-level condensation – vapor condenses into liquid droplets as it touches cooler ground surfaces • Dew Point = temp. at which atmospheric vapor condenses – varies depending on the humidity (how much vapor is in the air)
  27. 27. Frost • Frozen dew – water vapor skips liquid form and freezes as it touches below 0oC ground surfaces

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