Unique Nature of Pure Water
What type of bond holds water molecules together, giving it high surface tension?
Hydrogen bonds
What is the average salinity of ocean water?
About 35‰ (parts per thousand)
What gas dissolves in seawater to form carbonic acid?
Carbon dioxide (CO₂)
What is the major ion that makes seawater salty?
Chloride (Cl⁻)
What is the main reservoir of carbon on Earth?
The ocean
What is the angle between the two hydrogen atoms in a water molecule?
About 104.5°
How does increasing salinity affect the density of seawater?
Higher salinity increases density
What happens to ocean pH as more CO₂ dissolves in seawater?
It decreases (becomes more acidic)
What law states that the ratio of major ions in seawater remains constant regardless of salinity?
Forchhammer’s Principle (Principle of Constant Proportions)
What process moves carbon from the atmosphere into the ocean?
Gas exchange (dissolution of CO₂ into seawater)
Why is water considered a polar molecule?
Because it has a partial positive charge on the hydrogens and a partial negative charge on the oxygen
What two factors primarily control the density of seawater?
Temperature and salinity
What ion concentration decreases as ocean acidification progresses, threatening shell-building organisms?
Carbonate ion (CO₃²⁻)
What is the pH range of typical seawater?
Around 7.5–8.4
What is the term for the movement of carbon through organisms, the atmosphere, and the ocean?
The carbon cycle
What is the name of the property that allows water to stick to other substances?
Adhesion
What layer of the ocean experiences a rapid change in temperature with depth?
The thermocline
How does ocean acidification affect organisms like corals and mollusks?
It makes it harder for them to build calcium carbonate shells or skeletons.
How do dissolved gases like oxygen and carbon dioxide enter seawater?
Through diffusion from the atmosphere and biological activity
What process removes CO₂ from the atmosphere and converts it into organic carbon in the ocean?
Photosynthesis by phytoplankton
Explain why ice floats on water in terms of molecular structure.
Hydrogen bonding spaces water molecules farther apart in ice, making it less dense than liquid water.
Describe how temperature and salinity interact to influence water column stability.
Warm, less salty water is less dense and stays on top of cold, salty water, creating a stable stratification.
Explain the chemical reaction that occurs when CO₂ reacts with water in the ocean.
CO₂ + H₂O → H₂CO₃ → H⁺ + HCO₃⁻ (carbonic acid dissociates into hydrogen and bicarbonate ions)
Explain why oxygen concentrations are often low in deep ocean waters.
Because decomposition of organic matter consumes oxygen and limited mixing reduces replenishment.
Explain how the “biological pump” helps regulate Earth’s climate.
It transfers carbon from surface waters to the deep ocean as organic matter sinks, reducing atmospheric CO₂.