Unique Nature of Pure Water
What type of bond holds two hydrogen atoms to one oxygen atom in a water molecule?
Covalent bond
What is the average salinity of seawater in parts per thousand (ppt)?
About 35 ppt
What is the average pH of ocean water?
Around 8.1
What gas causes ocean acidification when absorbed by seawater?
Carbon dioxide (CO₂)
What form of carbon do plants and algae use during photosynthesis?
Carbon dioxide (CO₂)
What kind of bond forms between water molecules, giving water many of its unique properties?
Hydrogen bond
Which two ions make up most of the salt in seawater?
Sodium (Na⁺) and Chloride (Cl⁻)
What term describes a substance that resists changes in pH?
Buffer
What acid is formed when CO₂ reacts with water?
Carbonic acid (H₂CO₃)
What is the process by which organisms release CO₂ back into the atmosphere?
Respiration
What is the term for water’s ability to stick to itself?
Cohesion
How does increasing salinity affect the density of seawater?
Higher salinity increases density
What is the main buffering system in seawater?
The carbonate–bicarbonate system
How does ocean acidification affect shelled marine organisms?
It weakens or dissolves their calcium carbonate shells
What are the two main ocean carbon “pumps” that move carbon from surface waters to the deep ocean?
The biological pump and the solubility pump
Why does ice float on water?
Because ice is less dense than liquid water due to its open crystal structure.
What happens to seawater density as temperature decreases?
It increases
Why doesn’t the ocean become too acidic despite CO₂ dissolving in it?
Because of buffering by carbonate and bicarbonate ions
What human activity contributes most to ocean acidification?
Burning fossil fuels
How do oceans act as a carbon sink?
They absorb more carbon dioxide than they release
What property allows water to absorb large amounts of heat without changing temperature rapidly?
High specific heat capacity
What instrument is commonly used to measure salinity in seawater?
A refractometer or CTD (Conductivity, Temperature, Depth) sensor
What happens to carbonate ion concentration when more CO₂ dissolves in seawater?
It decreases
What chemical reaction represents ocean acidification’s impact on calcium carbonate shells?
CO₂ + H₂O + CaCO₃ → Ca²⁺ + 2HCO₃⁻
Why is the deep ocean an important part of the global carbon cycle?
It stores carbon for hundreds to thousands of years