Chemical and Physical Features of the Seawater and the World Oceans Chapter 3 Chemical and Physical Features of the Seawater and the World Oceans (Part 2)

MARINE BIOLOGY Essential Question: What are the chemical and physical properties of water? Learning Goals: Learn the composition of Seawater. Explore topics of Salinity Agenda: Bell Ringer Collect Homework Chapter 3 (Part 2) Classwork CNN/10 (3rd and 7th only) Upcoming: Chapter 3 (Part 3) Chapter 2 Test on 9/29

Bell Ringer What bonding occurs between individual water molecules? At what temperature is pure water most dense? In your own words define: Latent Heat of Melting Latent Heat of Evaporation.

Unique Nature of Water Water absorbs a great deal of heat before its temperature rises. Water has one of the highest heat capacities of any naturally occurring substance. Heat capacity: the amount of heat required to raise a substance’s temperature by a given amount.

Unique Nature of Water High heat capacity means that marine organisms because are not subject to the wide temperature ranges often seen on land Shallow waters are an exception to this rule Shallow bodies of water can warm up quickly due to the small volume of water

Unique Nature of Water A great deal of heat is also required for evaporation to occur. The amount of heat required for a substance to evaporate is known as the latent heat of evaporation. Water has the highest heat of evaporation of any naturally occurring substance.

Unique Nature of Water Water also acts as a solvent, which means that substances can dissolve in water. Water is the UNIVERSAL SOLVENT! Any substance dissolved in water is known as a solute. Ocean water has solutes dissolved in the water – we call the level of solutes salinity.

Seawater The characteristics of Seawater are due to the nature of water and the materials dissolved in it. Solids dissolved in seawater are produced by the chemical weathering of land rocks and are carried to the sea via rivers systems. Other materials come from earth’s interior through hydrothermal vents or are released into the atmosphere where they fall into the ocean as rain and snow.

Salty Solution The main solutes in ocean water are sodium and chloride (NaCl) This gives it a salty taste.

Salinity Salinity: total amount of salts dissolved in seawater measured in parts per thousand (ppt). Salinity is normally around 35 ppt, however, this can vary by location. This means that for every 1000 grams of water, there are 35 grams of salt.

Majority Solutes in Seawater Seawater contains a little of almost everything! BUT…. 99% of solute material is composed of only 6 ions! Chloride Sodium Sulfate Magnesium Calcium Potassium

Salinity Ocean water near a location where a river meets the sea can be 15-25 ppt. (less than normal salinity) Other areas can be higher than normal, if evaporation is high and no rivers are contribute freshwater to that area. Ex. The Dead Sea, Israel (34% Salinity) & Don Juan Pond, Antarctica (40% Salinity)

Unique Nature of Water Water is also relatively transparent (you can see through it). This means that sunlight shining on the surface can penetrate the surface (great for those photosynthetic organisms living under the sea) This level of penetration varies greatly depending on the amount of solutes in the water.

Unique Nature of Water To illustrate that point, imagine the crystal clear waters of the Bahamas (or other tropical locations you may have visited or seen in photos). Compare this with the less transparent water at the NC coast. The difference is rivers. Several rivers in North Carolina empty into the Atlantic. This means more solutes and less transparency (we sometimes also call this visibility).

Adding Water and Solutes to the Oceans Water comes from… Rivers Precipitation (rain, snow) Melting of polar ice. Solutes come from… weathering of rocks hydrothermal vents Land run off from rivers