Properties of Ocean Water Flashcards

A complete set of practice Q&A flashcards reviewing properties of ocean water, water chemistry, salinity calculations, density, ocean layering, turbidity, and dissolved gases based on lecture notes.

What is the molecular structure and partial charge distribution of a water molecule ($H_2O$)?

A water molecule consists of 2 hydrogen atoms and 1 oxygen atom. It is polar, with slightly positive partial charges on the hydrogen ends and a slightly negative partial charge on the oxygen end.

How do polar covalent bonds and hydrogen bonds differ in water?

A polar covalent bond occurs within one water molecule where oxygen and hydrogen share electrons unevenly. A hydrogen bond occurs when the slightly positive hydrogen of one water molecule attracts the slightly negative oxygen of another water molecule.

What are the density and spacing differences between solid ice and liquid fresh water?

Solid ice has an organized pattern with gaps and a density of about $0.9\,g/cm^3$, while liquid fresh water has molecules close together and a density of about $1.0\,g/cm^3$.

What are the freezing points of fresh water and typical seawater?

Fresh water freezes at $0\,^\circ\text{C}$ ($32\,^\circ\text{F}$), whereas typical seawater freezes at about $-1.8\,^\circ\text{C}$.

Why does ice float on liquid water?

Ice floats because its open structure makes it less dense ($0.9\,g/cm^3$) than liquid water ($1.0\,g/cm^3$).

How is salinity defined and measured in average ocean water?

Salinity is the amount of dissolved salts in water, measured in parts per thousand ($ppt$). Average ocean salinity is about $35\,ppt$, which equals $35\,g$ of salt per $1,000\,g$ of seawater.

Which tool is used to measure salinity?

A refractometer.

Which processes act as freshwater inputs, and how do they affect salinity?

Rainfall, river runoff, and ice melting act as freshwater inputs, which add fresh water and decrease salinity.

Which processes act as freshwater outputs, and how do they affect salinity?

Evaporation and sea ice formation act as outputs, removing water or leaving salt behind, which increases the salinity of the remaining water.

Why does the Amazon River mouth have a lower surface salinity ($30\text{--}34\,ppt$)?

Because the Amazon River adds large amounts of fresh water to the ocean.

Why is salinity higher ($36\text{--}38\,ppt$) around $20^\circ\text{--}30^\circ$ north and south latitude?

Those regions experience high evaporation and little rainfall.

What classroom formula is used to approximate salinity in parts per thousand ($ppt$)?

$$\text{Salinity (ppt)} = \frac{\text{salt (g)}}{\text{water volume (mL)}} \times 1,000$$

How many grams of salt are needed to prepare a $500\,mL$ solution with a target salinity of $35\,ppt$?

$17.5\,g$ of salt ($\text{Salt needed (g)} = 35\,ppt \times 0.5\,L$).

How do temperature and salinity affect seawater density?

Saltier water is denser than fresher water at the same temperature, and cold seawater is denser than warm seawater at the same salinity. Seawater has a density of about $1.03\,g/cm^3$ compared to fresh water at $1.0\,g/cm^3$.

At what temperature is fresh water at its maximum density?

Fresh water is densest near $4\,^\circ\text{C}$.

What are the three main temperature layers of the ocean from top to bottom?

1. Surface mixed layer (warm and uniform)
2. Thermocline (temperature drops quickly with depth)
3. Deep cold layer (cold, around $2\text{--}4\,^\circ\text{C}$)

What is turbidity, and how do the Amazon River and the Bahamas differ in turbidity?

Turbidity measures how cloudy water is due to suspended particles. The Amazon River has high turbidity (muddy, brown water), whereas the Bahamas has low turbidity (clear water).

Why do coastal waters generally contain more nutrients than open-ocean surface waters?

Because rivers and runoff carry materials and nutrients from land, such as nitrogen and phosphorus, into coastal waters.

How does dissolved oxygen ($O_2$) enter the ocean and reach deep waters?

Dissolved oxygen enters surface water from the atmosphere and photosynthesis in sunlit water, and ocean circulation transports it to deep water.