Videos from sea floor

• http://www.youtube.com/watch?v=hmMlspNoZMs

• http://www.youtube.com/watch?v=rFHtVRKoaUM

Do Now

• Use your textbook to look up and write down the definitions to the following terms• Heat capacity• Latent heat of melting• Latent heat of evaporation

Chemical and Physical Features of Seawater and

the World OceanChapter 3

Surface Tension

• http://www.youtube.com/watch?v=2suY9h7xnKg

Hydrogen Bonds

• Attractions between water molecules • Weak • Temperature reflects average speed of the

molecules• D=m/v• As sea water gets colder, it gets more

dense.

Less Dense Frozen

Melting Ice

• Takes a lot of heat. • Hydrogen bonds have to be broken.• The amount of heat required to melt a

substance is called the latent heat of melting

• http://www.youtube.com/watch?v=MpDJmRydR04

Heat capacity

• The amount of heat it takes to raise a substances temperature by a given amount.

• Water has a high heat capacity

Latent heat of evaporation

• Water absorbs a great deal of heat when it evaporates.

Universal Solvent

• Water is very good at dissolving salts• Charged atoms or groups of atoms are

known as ions• Salts have much stronger electric charges

than the opposite end of the water molecule.

• Bonds between ions are stronger than hydrogen bonds

Water dissolves salt

Seawater

• Characteristics of seawater are due to the nature of pure water and solutes

• Weathering• Volcanoes• Hydrothermal vents.

Salt composition

• Seawater contains a little of almost everything, most of the solutes are made up of a small group of ions

• 6 ions compose over 99% of the solids dissolved in seawater

• Sodium chloride accounts for 85%

Salinity

• The total amount of salt dissolved in seawater• How is it expressed?• Parts per thousand

• Because of the electrical charges ions are good conductors of electricity

• Electric conductivity of seawater therefore reflects salt concentration• Practical salinity units (psu)

Salinity on organisms

• Organisms are affected by total amount of salt and the type of salt

• Examine salts left after evaporation

Table 3.1

Rule of constant proportions

• William Dittmar – chemist analyzed samples from the Challenger expedition.

• Found that percentage of the various ions in seawater remained constant even though the total amount of salt varied from place to place

• Oceans are chemically well mixed• Varies by addition or subtraction of pure

water

Average Salinity

• 35 0/00• Open ocean varies little between 33 0/00

and 37 0/00• The variation mostly depends on

evaporation and precipitation

Red Sea

• The Red Sea is very salty • About 40 0/00

• Salinity affects the density of water like temperature• Salty water is more dense than freshwater

• Discovery Ed Red Sea clip

Salt water

• Freezes at a lower temperature that freshwater

• Oceans are less prone to freezing than lakes and rivers are

• Temperature varies more in the ocean than salinity • Open ocean range is about -2 degrees C and

30 degrees C

Do Now

Measuring temp. and salinity

• Specially designed bottles and thermometers on a wire to the desired depth

• A weight known as a messenger is released to slide down the wire.

• Temperature profile

Temperature profile

CTDs

• Conductivity, temperature and depth in the water column

• Used along with other instruments. • Bathythermographs – measure temp but not

salinity

Complications w/ samples

• What are some complications that scientists may face when collecting samples?

• Hmm..• Trying to get samples from multiple sites• Weather and climate variability

Solutions

• What are some solutions to these problems?

• Hmm…• Instruments could drift with the currents