Ocean Water ChemistryOcean Water Chemistry

Chap 14, Sec 4Chap 14, Sec 4

Essential Questions:Essential Questions:

1.1. How salty is ocean water?How salty is ocean water?

2.2. Why is the ocean salty?Why is the ocean salty?

3.3. Why doesn’t the salinity change Why doesn’t the salinity change drastically?drastically?

4.4. How do the temperature and gas How do the temperature and gas content of ocean water vary?content of ocean water vary?

5.5. How do conditions in the ocean How do conditions in the ocean change with depth?change with depth?

What is Ocean water made What is Ocean water made of?of?• WaterWater

• Dissolved gasesDissolved gases– Such as oxygen, carbon dioxide, and nitrogenSuch as oxygen, carbon dioxide, and nitrogen

• Dissolved saltsDissolved salts– Such as chloride, sodium, sulfate, magnesium, Such as chloride, sodium, sulfate, magnesium,

calcium, and potassiumcalcium, and potassium• Calcium, magnesium, and sodium come from rocks Calcium, magnesium, and sodium come from rocks

and are dissolved slowly by rivers and groundwaterand are dissolved slowly by rivers and groundwater

• Sulfate and chloride come from erupting volcanoesSulfate and chloride come from erupting volcanoes

Salts in SeawaterSalts in Seawater• Sodium and chloride make up 85 % of ions Sodium and chloride make up 85 % of ions

in saltwater. When removed from water in saltwater. When removed from water these combine to make halite (common these combine to make halite (common table salt).table salt).

• Salinity is the measure of the amount of Salinity is the measure of the amount of salts dissolved in seawater. One kilogram salts dissolved in seawater. One kilogram of seawater contains about 35 g of of seawater contains about 35 g of dissolved salts (3.5 %)dissolved salts (3.5 %)

•This meansThis means……If you boiled a ……If you boiled a kilogram of ocean water in a pot until all the kilogram of ocean water in a pot until all the water was gone, there would be about 35 water was gone, there would be about 35 grams of salt left in the pot.grams of salt left in the pot.

Differences in SalinityDifferences in Salinity• Warm ocean water has higher salinity than Warm ocean water has higher salinity than

cold ocean water because the water often cold ocean water because the water often evaporates and leaves salts behind.evaporates and leaves salts behind.

• Pure ocean water has higher salinity than Pure ocean water has higher salinity than water that has mixed with fresh water – water that has mixed with fresh water – such as where a river empties into the such as where a river empties into the ocean.ocean.

• Surface water is lower in salts than deeper Surface water is lower in salts than deeper water because of rain, freshwater mixing in, water because of rain, freshwater mixing in, melting ice and such.melting ice and such.

• Water near the poles is saltier than other Water near the poles is saltier than other places because the salt doesn’t freeze with places because the salt doesn’t freeze with the water – which leaves more salt there.the water – which leaves more salt there.

Steady State of the OceansSteady State of the Oceans

• The oceans are in balance because the salinity The oceans are in balance because the salinity has remained constant for hundreds of millions of has remained constant for hundreds of millions of years. Scientists have gathered evidence that years. Scientists have gathered evidence that says the oceans are not growing saltier.says the oceans are not growing saltier.

• Rivers, volcanoes, and the atmosphere constantly Rivers, volcanoes, and the atmosphere constantly add material to the oceans.add material to the oceans.

• Organisms use dissolved salts to make shells, Organisms use dissolved salts to make shells, marine animals remove calcium ions from the marine animals remove calcium ions from the water to form bones, other animals use the water to form bones, other animals use the dissolved calcium to form shells.dissolved calcium to form shells.

• Elements are added to the ocean at about the Elements are added to the ocean at about the same rate as they are removed.same rate as they are removed.

Salinity affects the properties Salinity affects the properties of water.of water.

• Ocean water freezes at a lower Ocean water freezes at a lower temperature than fresh water (at temperature than fresh water (at 28.5828.58° ° instead of 32instead of 32°° ) )

– Ocean water is denser than fresh Ocean water is denser than fresh water. As a result, water. As a result, 1.1. Salt water weighs more than fresh waterSalt water weighs more than fresh water

2.2. you can float more easily in ocean water you can float more easily in ocean water than in fresh water (buoyancy increases)than in fresh water (buoyancy increases)

– Look at the picture on page 374!Look at the picture on page 374!

Other Ocean PropertiesOther Ocean Properties

• Surface temperatures of the Surface temperatures of the ocean vary (just like on land) ocean vary (just like on land) with location & seasonswith location & seasons

• Gases in ocean water vary as Gases in ocean water vary as well.well.

Ocean Surface TemperatureOcean Surface Temperature

• The ocean absorbs energy from the The ocean absorbs energy from the sun. Near the equator, the sun. Near the equator, the temperature at the surface of the temperature at the surface of the ocean is about 25°C— ( 77ocean is about 25°C— ( 77°° F) about F) about room temperature. The temperature room temperature. The temperature drops as you go away from the drops as you go away from the equator.equator.

Gases in the Ocean Vary:Gases in the Ocean Vary:• Ocean organisms use gases in ocean Ocean organisms use gases in ocean

water. Two gases that ocean organisms water. Two gases that ocean organisms use are carbon dioxide and oxygen. use are carbon dioxide and oxygen. Algae, for example, need carbon dioxide Algae, for example, need carbon dioxide to carry out photosynthesis. Ocean to carry out photosynthesis. Ocean animals need oxygen.animals need oxygen.

• There is much more carbon dioxide in the There is much more carbon dioxide in the ocean than in the air. There is much less ocean than in the air. There is much less oxygen in the ocean than in the air. oxygen in the ocean than in the air. Surface water has more oxygen in it than Surface water has more oxygen in it than deeper water has.deeper water has.

Changes With DepthChanges With Depth

• As you descend through the As you descend through the ocean, the water temperature ocean, the water temperature decreases. decreases. – The deeper you go in the ocean, the The deeper you go in the ocean, the

colder and denser the water is. Cold water colder and denser the water is. Cold water is denser than warm water (which means is denser than warm water (which means it rises).it rises).

• Pressure increases continuously Pressure increases continuously with depth in the ocean.with depth in the ocean.

- Ocean Water Chemistry

Changes with DepthChanges with Depth

• Temperature Temperature decreases as depth decreases as depth increases.increases.

• Pressure increases Pressure increases as depth increases.as depth increases.

• Light decreases as Light decreases as depth increases.depth increases.

Water PressureWater Pressure

• If you could drop from the ocean’s surface to the If you could drop from the ocean’s surface to the ocean floor, you would pass through a section of the ocean floor, you would pass through a section of the ocean known as the water column. Conditions change ocean known as the water column. Conditions change as you go from the top of the water column to the as you go from the top of the water column to the bottom.bottom.

• There are three temperature zones in the water There are three temperature zones in the water column. The surface zone is warmest. The transition column. The surface zone is warmest. The transition zone begins at about 1 kilometer (.6 miles) down. zone begins at about 1 kilometer (.6 miles) down. Temperatures drop quickly in the transition zone. Temperatures drop quickly in the transition zone. Below the transition zone is the deep zone, where the Below the transition zone is the deep zone, where the water is very cold.water is very cold.

• Water pressure is the force of the weight of water. Water pressure is the force of the weight of water. Because of high pressure in the deep ocean, divers Because of high pressure in the deep ocean, divers can go down safely to only about 40 meters (131 can go down safely to only about 40 meters (131 feet).feet).

Essential Questions - Essential Questions - Answered:Answered:1.1. How salty is ocean water?How salty is ocean water?

• 3.5% - 1 kilogram of ocean water contains 3.5% - 1 kilogram of ocean water contains 35 grams of salts35 grams of salts

2.2. Why is the ocean salty?Why is the ocean salty?• The ocean is salty because salts are The ocean is salty because salts are

dissolved from rock by water flowing to dissolved from rock by water flowing to the oceans.the oceans.

3.3. Why doesn’t the salinity change Why doesn’t the salinity change drastically?drastically?

• The oceans are balanced. About as much The oceans are balanced. About as much salt is added as is removed.salt is added as is removed.

Answers ContinuedAnswers Continued

4.4. How do the temperature and gas content How do the temperature and gas content of ocean water vary?of ocean water vary?

• Temperature varies based on latitude and Temperature varies based on latitude and seasons. Gas content varies based on seasons. Gas content varies based on temperature – cold water contains more temperature – cold water contains more oxygen while warm water contains more oxygen while warm water contains more carbon dioxide.carbon dioxide.

5.5. How do conditions in the ocean change How do conditions in the ocean change with depth?with depth?

• As depth increases, temperature decreases, As depth increases, temperature decreases, light decreases, and the pressure increases.light decreases, and the pressure increases.