Unique Nature of Pure Water
Covalent bonds
What type of bond holds two hydrogen atoms and one oxygen atom together in a water molecule?
Salinity is the amount of dissolved salts in water.
What is salinity?
The most abundant ion is chloride (Cl⁻), followed by sodium (Na⁺).
What is the most abundant dissolved ion in seawater?
The gas responsible is carbon dioxide (CO₂)
What gas is mainly responsible for ocean acidification?
Photosynthesis is the process plants and algae use to absorb CO₂
What process do plants and algae use to take in carbon dioxide from the atmosphere?
Water is polar because oxygen is slightly negative and hydrogen is slightly positive, creating opposite charges on each end.
Why is water considered a polar molecule?
Salinity changes due to evaporation, precipitation, river runoff, or melting/freezing of ice.
Name two factors that can change the salinity of seawater.
8.1
What is the average pH of seawater?
CO₂ reacts with water to form carbonic acid (H₂CO₃)
What gas is mainly responsible for ocean acidification?
Carbon moves from the atmosphere to the ocean by diffusion, where CO₂ dissolves into surface water.
How does carbon move from the atmosphere into the ocean?
Hydrogen bonds make water boil and freeze at higher temperatures than expected, because they require more energy to break.
How does hydrogen bonding affect water’s boiling and freezing points?
Colder water is denser than warm water; as temperature decreases, density increases.
How does temperature affect the density of seawater?
The rule of constant proportions means that although total salinity varies, the relative ratios of major ions in seawater remain constant.
Explain the concept of the “rule of constant proportions” in seawater chemistry.
Increased acidity dissolves calcium carbonate, weakening shells and skeletons of corals, mollusks, and plankton.
How does ocean acidification affect organisms that use calcium carbonate to build shells or skeletons?
Marine organisms use carbon to build shells and skeletons; when they die, this carbon can become part of sediments or limestone, storing it long-term.
Describe how marine organisms contribute to the long-term storage of carbon.
Ice floats because it’s less dense than liquid water; the hydrogen bonds spread the molecules apart when frozen. This lets life survive under the ice.
Explain why ice floats on liquid water and how this benefits marine life in cold climates.
Stratification occurs because layers form where warmer, less dense water sits on top of colder, saltier, denser water.
Why do layers form in the ocean based on temperature and salinity (stratification)?
Photosynthesis uses CO₂ and produces oxygen; respiration and decomposition use oxygen and release CO₂.
How do chemical processes such as photosynthesis and respiration affect oxygen and carbon dioxide levels in seawater?
As shell-building species decline, entire food webs are disrupted, affecting fish and animals that depend on them
Explain how increased acidity can impact the marine food web.
The ocean acts as a carbon sink by absorbing more carbon than it releases, helping balance Earth’s carbon and reduce global warming.
Explain the role of the ocean as a carbon sink and why it’s important for regulating Earth’s climate.
Water’s high heat capacity allows it to absorb and release large amounts of heat without changing temperature much, keeping Earth’s climate and ocean temperatures stable.
Describe how water’s high heat capacity helps regulate Earth’s climate and ocean temperatures.
Global warming can cause surface waters to warm and mix less with deeper layers, reducing nutrient circulation and oxygen levels that marine life needs.
An example of how global warming could change the physical layering of the ocean and explaination why this matters to marine ecosystems.
High nutrient runoff causes eutrophication, which increases algae growth, depletes oxygen, and changes the chemical balance of seawater.
Describe how the chemical composition of seawater might change in areas with high nutrient runoff from land.
Solutions include reducing CO₂ emissions by using renewable energy, protecting mangroves and seagrasses that absorb carbon, and improving global carbon management
Propose a potential solution or global action that could help slow the rate of ocean acidification and describe how it would work
Human activities like burning fossil fuels and deforestation increase CO₂, disrupting natural carbon storage and leading to acidification and climate change in marine systems.
Analyze how human activities, such as burning fossil fuels, have disrupted the natural carbon cycle in marine environments.