Unique Nature of Pure Water
What type of molecule is water — polar or nonpolar?
Polar
What is the term for the amount of dissolved salts in seawater?
Salinity
What two ions make up most of the salt in the ocean?
Sodium and chloride
What is the main human activity causing ocean acidification?
Burning fossil fuels
What form of carbon do plants and algae take in during photosynthesis?
Carbon dioxide (CO₂)
What causes water molecules to “stick” together?
Hydrogen bonding
How does increasing salinity affect seawater’s density?
It increases the density.
What is the main reason seawater is slightly basic?
It contains dissolved carbonate and bicarbonate ions.
What happens when CO₂ reacts with seawater?
It forms carbonic acid.
What is released when organisms break down food for energy?
Carbon dioxide
Why does water have surface tension?
Because of strong cohesion between molecules at the surface
What physical property decreases with depth in most parts of the ocean?
Temperature
What is the range of normal seawater pH?
Around 7.8 to 8.4
How does ocean acidification impact coral reefs?
It makes it harder for corals to build calcium carbonate skeletons.
What role does the ocean play in the carbon cycle?
It acts as a major carbon sink, absorbing CO₂ from the atmosphere.
Why can ice float on liquid water?
Ice is less dense because the molecules spread apart as it freezes.
What process causes the formation of sea ice to raise the salinity of nearby water?
Freezing removes fresh water, leaving salt behind.
What natural process helps maintain the chemical balance of the ocean?
The buffering system between carbonic acid, bicarbonate, and carbonate
What happens to carbonate ion concentration as acidity increases?
It decreases.
How does carbon become stored long-term in the ocean?
It settles as sediments or gets trapped in shells and rocks.
How does water’s high heat capacity benefit Earth’s climate?
It helps regulate temperature by absorbing and releasing heat slowly.
What term describes layers of seawater with different densities that resist mixing?
Stratification
Why doesn’t seawater composition change much even when evaporation occurs?
Because the proportions of dissolved ions stay constant
Why is ocean acidification a threat to the food chain?
It affects shell-forming plankton that are the base of marine food webs.
What human impact has disrupted the natural carbon cycle?
Excess carbon emissions from deforestation and fossil fuel burning.