Ocean Water Chemistry

What is the average salinity of the ocean?

• 3%

• 3.5%

• 4%

• 4.5%

Answer explanation

The correct average salinity of the ocean is 3.5%, making it the most accurate choice among the options provided.

Select two reasons as to why salinity can INCREASE

• Evaporation because water is changing into water vapor leaving salt behind.

• Freshwater is added to the ocean at the mouths of large rivers as they empty freshwater into oceans.

• Freshwater is added by rain, snow, and melting ice.

• Surface water freezes into ice, leaving salt behind.

Answer explanation

Salinity can increase due to evaporation, which leaves salt behind as water changes into vapor, and when surface water freezes into ice, leaving salt behind.

Select two reasons as to why salinity can decrease.

• Evaporation because water is changing into water vapor leaving salt behind.

• Freshwater is added to the ocean at the mouths of large rivers as they empty freshwater into oceans.

• Freshwater is added by rain, snow, and melting ice.

• Surface water freezes into ice, leaving salt behind.

Answer explanation

Salinity can decrease when freshwater is added to the ocean at the mouths of large rivers and through rain, snow, and melting ice, diluting the salt content in the water.

Tags

NGSS.MS-ESS2-4

Where do oceans have the lowest salinity?

• along the ocean floor

• at the equator

• on the north pole

• where rivers flow into the ocean

Answer explanation

Oceans have the lowest salinity where rivers flow into the ocean, as freshwater dilutes the salt content.

The density of ocean water is influenced by what two factors?

• Salinity and temperature

• Water color and chlorophyll

• Dissolved gases and dissolved solids

• Dissolved carbon and trace elements

Answer explanation

The density of ocean water is influenced by salinity and temperature, as these factors affect the mass of water molecules and their arrangement.

Where would you find the lowest density seawater?

• surface zone

• deep zone

• transition zone

• abyssal zone

Answer explanation

The lowest density seawater is found in the surface zone due to factors like temperature, salinity, and exposure to sunlight.

Which processes decrease salinity?

• freezing

• melting sea ice

• precipitation

• surface runoff from land

• evaporation

Answer explanation

Processes that decrease salinity include melting sea ice, precipitation, and surface run off from land.

Which processes increase salinity?

• evaporation

• surface runoff from land

• precipitation

• freezing

• melting

Answer explanation

Processes that increase salinity include evaporation and freezing, as they concentrate the salt content in the remaining water.

Which of the following would have the lowest salinity?

• Middle of the Ocean

• Mouth of a river

• Dead Sea

• Bottom of a trench

Answer explanation

The mouth of a river would have the lowest salinity because freshwater from the river dilutes the salt content in the surrounding water.

What is the primary component of ocean water?

• Sodium chloride

• Calcium carbonate

• Magnesium sulfate

• Potassium bromide