Seawater Composition

Seawater is a complex mixture of dissolved solids, gases, and organic substances. The composition of seawater is influenced by various factors including evaporation, precipitation, river inflow, and biological processes.

Major Components of Seawater

Salinity: The total amount of dissolved salts in seawater, usually expressed in parts per thousand (ppt). The average salinity of seawater is about 35 ppt.
Water: The primary component of seawater, making up about 96.5% of its mass.
Chloride: The most abundant ion in seawater, making up about 55% of the total dissolved ions.
Sodium: The most abundant cation in seawater, making up about 30.6% of the total dissolved ions.
Magnesium and Sulfate: Other major ions found in seawater, making up significant proportions of the dissolved solids.

Minor Components of Seawater

Calcium and Potassium: These ions are present in lower concentrations compared to sodium and chloride.
Trace Elements: Seawater contains a wide range of trace elements such as iron, zinc, copper, and manganese, which play important roles in biological processes.
Gases: Seawater also contains dissolved gases such as oxygen, carbon dioxide, and nitrogen, which are essential for marine life.

Factors Affecting Seawater Composition

The composition of seawater can be influenced by several factors:

Evaporation and Precipitation: Evaporation increases salinity, while precipitation decreases it.
River Inflow: Freshwater inflow from rivers can dilute seawater, affecting its composition near river mouths.
Biological Processes: Marine organisms can remove or add certain ions and organic substances to seawater, altering its composition.

Study Tips

When studying seawater composition, it's important to focus on the major components, understand the concept of salinity, and be familiar with the factors that influence seawater composition. Additionally, practice identifying the major ions and trace elements found in seawater.

Try to relate the composition of seawater to its importance for marine life and global processes such as the water cycle and climate regulation.

Finally, make use of visual aids such as diagrams and charts to help you understand the relative proportions of different components in seawater.

◂Earth Science Worksheets and Study Guides High School. The Rock Cycle

Vocabulary/Answer key

The Rock Cycle

Vocabulary/Answer key

The Rock Cycle

Vocabulary/Answer key

The Rock Cycle

The resources above cover the following skills:

EARTH AND SPACE SCIENCE (NGSS)

Earth’s Systems

Students who demonstrate understanding can:

Develop a model to illustrate how Earth’s internal and surface processes operate at different spatial and temporal scales to form continental and ocean-floor features.

EARTH AND SPACE SCIENCE (NGSS)

Earth’s Systems

Students who demonstrate understanding can:

Develop a model to illustrate how Earth’s internal and surface processes operate at different spatial and temporal scales to form continental and ocean-floor features.

EARTH AND SPACE SCIENCE (NGSS)

Earth’s Systems

Students who demonstrate understanding can:

Develop a model to illustrate how Earth’s internal and surface processes operate at different spatial and temporal scales to form continental and ocean-floor features.

EARTH AND SPACE SCIENCE (NGSS)

Earth’s Systems

Students who demonstrate understanding can:

Develop a model to illustrate how Earth’s internal and surface processes operate at different spatial and temporal scales to form continental and ocean-floor features.