The Sea Around Us Lecture 4: 23 January 14 Water is The Wonder Substance: Physical & Chemical Properties Drown with Me Porcupine Tree. Thanks to Zach R. Ocean Breathes Salty Modest Mouse Water Cycle Jump!

Lecture Review Questions:Lecture Review Questions: TA Office Hours (T & W 11-12) On-line Assignment 2 is due tonight by 11pm Homework 1 is available on Angel Cell Phone Recycling Book pics! (Angel dropbox) Thanks to Wanyu L. Read Chap. 5 of Trujillo and Thurman (on reserve in EMS Library, Deike Bld)

Lecture Review Questions:Lecture Review Questions: TA Office Hours (T & W 11-12) On-line Assignment 2 is due tonight by 11pm Homework 1 is available on Angel Cell Phone Recycling Book pics! (Angel dropbox) Thanks to Sze Yu Y. Read Chap. 5 of Trujillo and Thurman (on reserve in EMS Library, Deike Bld)

Florida couple planning for life under the sea cience/story.aspx?storyid= &catid=67 World Ocean CouncilWorld Ocean Council See link for Internship Program.

Water Promotes Continuity of Life on Earth Low viscosity rapid flow to equalize pressure differences High surface tension allows wind energy to be transmitted to sea surface allows cells to hold shape --and life to form controls the behavior of water drops High heat capacity cools/warms slowly relative to land aids in heat retention & transport minimizes extremes in temperature helps to maintain uniform body temps High latent heat of evaporation very important in heat/water transfer in atmosphere

Heat (cal, or Joules) Temperature (°C) water Heat, Temperature and Changes of Phase Which statement is correct about this plot? Ice changes to water (melts!) at 0° C If we add heat to water (or ice) the temperature rises, this is known as sensible heat Heat is required to change the phase of a substance (for example, ice to water); this is known as latent heat Ice Latent heat Sensible heat

Latent Heat and Changes of State Latent heat of fusion (or melting) Heat to form or melt ice (liquid to solid phase) 333 kJ/kg (80 calories/gram) Latent heat of vaporization (or precipitation) Heat to vaporize (boil) a liquid or condense liquid from a gas phase 2260 kJ/kg (540 calories/gram) Evaporation of water from the surface can occur at any temperature. However, it takes more energy to evaporate at low T than to boil off vapor once water reaches 100°C

Heat Capacity Heat required to change the temperature (by 1 °) of a given mass Heat input (J/kg or cal/gram) Liquid water Rock & Soil 4190 Kg °C J Temperature (°C)

Heat Capacity Heat required to change the temperature (by 1 °) of a given mass Heat input (J/kg or cal/gram) Temperature (°C) Liquid water Rock & Soil Pepsi

Heat Capacity Heat required to change the temperature (by 1 °) of a given mass Heat input (J/kg or cal/gram) Temperature (°C) Liquid water Rock & Soil

Heat Capacity Heat required to change the temperature (by 1 °) of a given mass Heat input (J/kg or cal/gram) Temperature (°C) Liquid water Rock & Soil

Heat Capacity Heat required to change the temperature (by 1 °) of a given mass Heat input (J/kg or cal/gram) Temperature (°C) Liquid water Rock & Soil

Heat Capacity Heat required to change the temperature (by 1 °) of a given mass Heat input (J/kg or cal/gram) Temperature (°C) Liquid water Rock & Soil

Heat Capacity Heat required to change the temperature (by 1 °) of a given mass Heat input (J/kg or cal/gram) Temperature (°C) Liquid water Rock & Soil

Heat capacity and phase changes: ice (solid) water (liquid) vapor or steam (gas) Heat input (cal/gram) Temperature (°C) Liquid water Ice Vapor Latent Heat Heat needed to change phase (from solid to liquid, liquid to gas, liquid to solid, etc.) Latent heat of vaporization or condensation 540cal/gm Latent heat of fusion or melting 80cal/gm Ice + liquid vapor+ liquid

Clicker question: Which is the best answer A.Viscosity is a measure of resistance to shear motion A.A low viscosity liquid pours more slowly than a high viscosity liquid B.The viscosity of water is zero C. Water is highly compressible, which means that 1 kg of it occupies a much, much smaller volume at the bottom of the ocean than near the ocean surface D.A & D

Consider: two identical pots, filled with equal masses of fluid, on identical burners on a stove. Pot A is filled with a fluid of low heat capacity Pot B is filled with a fluid of high heat capacity After a time….. A.The material in Pot A has reached higher temp. B.The material in Pot B has reached higher temp. C.Both pots are at the same temp. Heat Capacity is the heat required to change the temperature (by 1 °) of a given mass of material

The high heat capacity of water means that it heats up and cools off more slowly than land.

Latent heat is a key factor in Hurricane development and sustainability.

Properties of Water: Heat Capacity What is heat capacity? Why is it so high for H 2 0? Adding heat to water: speeds up molecules break bonds Hence, less warming or less evaporation than expected When heat is removed from water: bonds form and restructure, material condenses (e.g., gas to liquid) energy is released via bonds formation Energy release causes heating and thus temperature decrease is smaller than expected

Density of Fresh Water & Ice Ice is less dense than water. Ice at 0 °C is kg/m 3 Ice has an open hexagonal structure: Ice density is lower than water Water molecular structure Ice molecular structure

Density of Water Fresh water reaches maximum density at 3.98 °C Density= 1,000 kg/m 3 (1kg/liter) Density decreases as water is heated above 4°C At 20 °C, density of pure H 2 O is kg/m 3

How much heat energy is required to melt 10 grams of ice? A.80 calories B.540 calories C.800 calories D.54 calories E.5400 calories Heat input (cal/gram) Temperature (°C) Liquid water Ice Vapor Latent heat of evaporation 540cal/gm Latent heat of fusion or melting 80cal/gm

Hurricanes strengthen and gain energy by: A.Release of latent heat at high elevation within the eye, which causes air to warm-up and rise B.Release of latent heat associated with melting of ice particles, which makes air heavier C.Using their Lion card D.Absorbing heat from the sun E.None of the above

Heat capacity and phase changes: ice (solid) water (liquid) vapor or steam (gas) Latent Heat Heat needed to change phase (from solid to liquid, liquid to gas, liquid to solid, etc.)

Seawater is essentially an NaCl solution Average seawater salinity is 35 ppt (35 g/kg), but it varies from place to place Why the Sea is Salty 37 ppt 30 ppt Surface water salinity

Why the Sea is Salty

And over the eons of time, the sea has grown ever more bitter with the salt of the continents

Was the Chemistry of the Ancient Oceans the Same as Today? Time (billions of yrs) Ocean Salinity 35 0/00 Surface water salinity

Note the attraction of oppositely charged ends of water molecules for one another

Cl -, Na +, S0 4 -2, Mg +2, Ca +2, K + >99% of salt in sea water HC0 3 -2, Br -, Sr -2, B +2, F - (with these, 99.99%) Seawater is essentially an NaCl solution (saltwater)

All other elements occur at very low concentrations (ppm to ppb: to ) Seawater is essentially an NaCl solution Average seawater salinity is 35 ppt or 35 g/kg. Relative abundance of ions in seawater, in rank order: Cl, Na, SO 4, Mg, Ca, K (these make up >99% of the salt in seawater) HCO3, Br, Sr, B, F (with these >99.99% of the salt in seawater)

Charges must balance, therefore: Charge associated with cations: Na +, Mg +2, Ca +2, K + Must equal charge associated with anions: Cl -, SO 4 -2 Major ions in seawater keep “constant proportion,” regardless of salinity Except near river outlets (near coastal regions) Salinity (o/oo) ~1.81 x Chlorinity (o/oo)

But rivers are not the only important input And in soils

Ocean Chemistry is influenced by Erosion and Weathering of the land

For example, exchange of Magnesium (Mg) in seawater for Ca in ocean crust supplies excess Calcium Difference in chemical compositions between rivers and ocean --reflects sedimentation (precipitation) processes --other inputs/exchanges, such as basalt-seawater reactions at midocean ridges Rivers vs. Other Sources

Oceans: Chemical Inputs -rivers (weathering) -volcanic gases: HCl, SO 2, CO 2 -interaction of seawater with seafloor, e.g., hot basalt associated with Hydrothermal Circulation, this is a source of Ca and K Note: A volume of water equal to the entire ocean is circulated through seafloor material (crust) ~ every 10 m.y.

Ocean Chemistry is influenced by: A.By water interacting with rocks (Earth’s crust) at the mid-ocean ridges B.Evaporation of seawater C.River water D.Erosion and weathering of the land E.All of the above.