Ocean Chemistry

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

Water Is a Powerful Solvent

What are solutions and mixtures?•A solution is made of two components, with uniform molecular properties throughout:•The solvent, which is usually a liquid, and is the more abundant Component.

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

• The solute, often a solid or gas, is the less abundant component.

• Most mixtures are different from a solution, because solutions are homogenous mixtures. In a mixture the components retain separate identities, so it is NOT uniform throughout.

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

Salinity

Salinity is the total quantity of dissolved inorganic solids in water.

• The heat capacity of water decreases with increasing salinity

• As salinity increases, freezing point decreases

• As salinity increases, evaporation slows

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

http://www.youtube.com/watch?v=qeZgJzt3m04

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

A Few Ions Account for Most of the Ocean’s

Salinity

Mostly Sodium ChlorideAlso, Sulfate, Magnesium, Calcium and Potassium

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

Fig. 7-6, p. 192

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

Components of Ocean Salinity

The Earth’s Crust washes into the sea to add to the salinity of the ocean.

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

http://videos.howstuffworks.com/discovery/31886-howstuffworks-show-episode-4-ocean-water-video.htm

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

The Ocean Is in Chemical Equilibrium

Is the ocean becoming progressively saltier with age?

No, the ocean is in chemical equilibrium. The proportion and amounts of dissolved solids remain constant. This concept is known as the “steady state ocean.“

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

Gas Concentrations Vary with Depth

Oxygen is high at the surface and Carbon Dioxide is low. This is reversed as you increase in depth.

Carbon Dioxide makes up most of the dissolved gasses in the ocean.

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

Dissolved Oxygen is very important to aquatic life

Higher temperatures reduce the amount of dissolved oxygen

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

Fig. 7-12, p. 198

8.0 average ocean pH

pH7.0 7.5 8.5 9.0

0

Upper sunlit layer2,000

1,000 Bottom of photo-synthetic zone

4,000

6,0002,000

8,000

3,000 10,000

Dep

th (

m)

12,000 Dep

th (

ft)

4,000CCD 14,000

5,000 16,000

18,000

6,000

8.0

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

pH

The Ocean’s Acid-Base Balance Varies with Dissolved Components and Depth

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

pH changes as Carbon dioxide dissolves or as carbon is changed into Carbonate in the shells of animals.

The ocean becomes more acidic with more dissolved CO2

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

http://www.youtube.com/watch?v=MgdlAt4CR-4

http://www.youtube.com/watch?v=d0kacyyLVB4