General Chemistry

1. General Chemistry • Element • composed of atoms • Nucleus • protons and neutrons • electrons

2. General Chemistry • Molecule • a group of atoms held together by chemical bonds

3. General Chemistry • Bonds • covalent bonds form when electrons are shared

4. General Chemistry • Bonds • ionic bonds form by attraction between particles with opposite charges

5. Water • H2O • covalent bonds hold the 2 hydrogen & 1 oxygen together

6. Water • Water molecules have an uneven distribution of charge = polar • H positive • O negative

7. Water • Polar nature of water leads to: • attraction of other water molecules • attraction of other charged or polar molecules

8. Water • Hydrogen Bonds • form between hydrogen of one water molecule and the oxygen of another • cohesion

9. cohesion Water spider fnft

11. 3 “states” of Water • Solid • Liquid • Gas • (and it can go back and forth between these “states” many times!)

14. So you can have more than 1 state at a time…and why ice floats!

15. Water • Universal solvent • Solution • solvent • solute

16. Seawater • 96.5% water & 3.5% solutes • solutes change properties of water

18. Seawater • 96.5% water and 3.5% solutes • The SOLUTES are: 85% Salt (Sodium Chloride) and 15% “other.”

20. Seawater • Salinity • total concentration of all dissolved inorganic solids • average = 3.5% or 35 ppt (35o/oo)

22. Seawater • Source of ocean’s salts • weathering of surface rocks • sodium, magnesium, calcium • outgassing • chlorine, carbon dioxide, sulfur, hydrogen

24. Water is recycled continually between the ocean and the land • The reservoirs of water include: • Oceans: • cover 60% of the northern hemisphere • cover 80% of the southern hemisphere • contain 97% of Earth’s water • Rivers, lakes and glaciers • Groundwater • contains a larger volume of water than all of the combined water in lakes and rivers

25. The hydrologic cycledescribes the exchange of water between ocean, land and atmosphere. • On land precipitation exceeds evaporation. • In the ocean evaporation exceeds precipitation.

26. Recycling of Water

28. Heat vs Temperature • Heat • energy produced by the random vibration of atoms or molecules • Temperature • an objects response to the input or removal of heat energy

29. Heat Capacity • the heat required to raise the temperature of 1 gram of a substance by 1oC • Heat capacity of water = 1 calorie • the highest of all known substances • water resists changing temperature when heat is added or removed

30. Density and Temperature • density of water increases as water is cooled until a maximum of 1 g/cm3 is reached at 4oC • the density decreases as freezing takes place • ice is less dense than water

31. Why does ice float – ice is less dense than (liquid) water

32. Seawater vs. Pure Water • Seawater has a • lower heat capacity • lower freezing point • density increases until freezing point is reached • ice is pure water & cold, salty water left behind sinks

33. Density of Water • Depends on temperature and salinity • density increases as temperature decreases • density increases as salinity increases

34. Temp., Salinity and Density have a complex relationship – you can have the SAME density at different concentrations of Temp. and salinity.

35. Density Zones in the Ocean • 1. surface zone or mixed layer • temperature and salinity are constant with depth • 2. a middle layer where density changes rapidly with depth (because of extreme env. changes) = pycnocline • Thermocline: temp. changes rapidly w/ depth • Halocline: salinity changes rapidly w/ depth • NOTE: These 3 zones can ALL coincide together! 3. The DEEP ZONE (80% of all ocean water) is the layer below the pycnocline (but little change occurs here).

36. Fig 6-19, p.136

37. TheSurface Layer • About 100m thick • Comprises about 2% of the ocean volume • Is the most variable part of the ocean because it is in contact with the atmosphere. • Is less dense than the layers below because of its lower salinity or higher temperature.

38. Sea Surface Temperatures • Insolation and ocean-surface water temperature vary with the season. • Ocean temperature is highest in the tropics (25oC) and decreases poleward.

39. The Pycnocline • Is transitional between the surface and deep layers. • Comprises 18% of the ocean basin. • In the low latitudes, the pycnocline coincides with the thermocline. • In the mid-latitudes it coincides with the halocline.

40. Tropical and subtropical oceans are permanently layered with warm, less dense surface water separated from cold, dense deep water by a thermocline. • The thermocline is a layer in which water temperature and density change rapidly. • Temperate regions have a seasonal thermocline and polar regions have none.

41. The Deep Layer • Represents 80% of the ocean volume. • Water in the deep layer originates at the surface in high latitudes, where it: • cools • becomes dense • sinks to the sea floor • flows equatorward across the ocean basin

42. Density Zones in the Ocean • 3. the deep zone • a cold (1 to 3oC), dense layer on the bottom • most of the ocean (80%)

43. The water column in the ocean can be divided into the: • surface layer • pycnocline • deep layer

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47. Contrasting features of shallow and deep ocean water

48. Thermocline, Halocline, and Pycnocline

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50. Refraction, Light and Sound • Refraction: The “bending” of waves. Light and Sound are a direct result/reaction of these waves. • Light and Sound waves travel at DIFFERENT speeds depending upon the medium that they are in.