The Sea Around UsLecture 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:

• 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:

• 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

http://www.wtsp.com/news/science/story.aspx?storyid=169031&catid=67

World Ocean Council See link for Internship Program.

Water Promotes Continuity of Life on EarthLow viscosity

• rapid flow to equalize pressure differencesHigh 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)

Tem

pera

ture

(°C

)

water

Heat, Temperature and Changes of PhaseWhich 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

05

0-5

010 50

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

4190Kg °C

J-1 Te

mpe

ratu

re (

°C)

Heat Capacity Heat required to change the temperature (by 1 °) of a given mass

Heat input (J/kg or cal/gram)

Tem

pera

ture

(°C

)

Liquid water

Rock & Soil

10 50

20

10

30

Pepsi

Heat Capacity Heat required to change the temperature (by 1 °) of a given mass

Heat input (J/kg or cal/gram)

Tem

pera

ture

(°C

)

Liquid water

Rock & Soil

10 50

20

10

30

Heat Capacity Heat required to change the temperature (by 1 °) of a given mass

Heat input (J/kg or cal/gram)

Tem

pera

ture

(°C

)

Liquid water

Rock & Soil

10 50

20

10

30

Heat Capacity Heat required to change the temperature (by 1 °) of a given mass

Heat input (J/kg or cal/gram)

Tem

pera

ture

(°C

)

Liquid water

Rock & Soil

10 50

20

10

30

Heat Capacity Heat required to change the temperature (by 1 °) of a given mass

Heat input (J/kg or cal/gram)

Tem

pera

ture

(°C

)

Liquid water

Rock & Soil

10 50

20

10

30

Heat Capacity Heat required to change the temperature (by 1 °) of a given mass

Heat input (J/kg or cal/gram)

Tem

pera

ture

(°C

)

Liquid water

Rock & Soil

10 50

20

10

30

Heat capacity and phase changes: ice (solid)

water (liquid) vapor or steam (gas)

0 200 400 600 800Heat input (cal/gram)

Tem

pera

ture

(°C

)

150

100

-100

50

0

-50

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

B. A low viscosity liquid pours more slowly than a high viscosity liquid

C. The viscosity of water is zero

D. 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

E. 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 capacityPot 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 CapacityWhat is heat capacity? Why is it so high for H20?

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 formationEnergy 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 917.0 kg/m3

• 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/m3 (1kg/liter)

• Density decreases as water is heated above 4°C

• At 20 °C, density

of pure H2O is

998.23 kg/m3

How much heat energy is required to melt 10 grams of ice?

A. 80 caloriesB. 540 caloriesC. 800 caloriesD. 54 caloriesE. 5400 calories

0 200 400 600 800Heat input (cal/gram)

Tem

pera

ture

(°C

)

150

100

-100

50

0

-50

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 riseB. Release of latent heat associated with melting of ice particles,

which makes air heavierC. Using their Lion cardD. Absorbing heat from the sunE. 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 ppt30 ppt Surface water salinity

Why the Sea is Salty

Why the Sea is Salty

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

http://www.youtube.com/watch?v=BayExatv8lE

Was the Chemistry of the Ancient Oceans the Same as Today?

Time (billions of yrs)O

cean

Salin

ity

35 0/00

Surface water salinity

Note theattraction ofoppositely

charged ends ofwater moleculesfor one another

Cl-, Na+, S04-2, Mg+2, Ca+2, K+ >99% of salt in sea water

HC03-2, Br-, Sr-2, B+2, F- (with these, 99.99%)

http://www.webelements.com/

Seawater is essentially an NaCl solution (saltwater)

All other elements occur at very low concentrations (ppm to ppb: 10-6 to 10-9)

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, SO4, 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-, SO4

-2Major 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, SO2, CO2

-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.