Water on Earth and Its Properties

Water on Earth

• Earth is called the blue planet because of its abundance of water.
• Water is essential for all life and human activities.
• Water molecules consist of two hydrogen atoms and one oxygen atom.
• Water's use includes transport, excretion, chemical reactions, and plant support in small plants.
• Water is crucial for modern human activities like cooking, cleaning, agriculture, and manufacturing.
• Fresh water shortages exist though the water cycle replenishes fresh water.

Water's Molecular Structure and Properties

• Water molecules have a bent shape due to the bonding angles of hydrogen and oxygen.
• Water is a polar molecule with partial positive charges on hydrogen and a negative charge on oxygen.
• Water molecules can form hydrogen bonds.
• Only polar molecules dissolve in water.
• Water's unique properties are due to its polarity and hydrogen bonding.

Water Cycle

• The water cycle is the continuous movement of water on, above, and below Earth's surface.
• Key processes include evaporation, condensation, precipitation, sublimation, transpiration, runoff, and infiltration.
• Water transits from liquid to gas to liquid through these cyclical processes.
• The water cycle is crucial for maintaining life, weather, and ecosystems.
• Evapotranspiration combines evaporation from bodies of water and transpiration from plants.

Phase Changes of Water

• Phase changes (solid, liquid, gas) occur when energy or pressure changes.
• Processes include evaporation, condensation, sublimation, deposition, freezing, and melting.
• Critical point is where the liquid and vapor phases become indistinguishable.
• Triple point is where all three phases (solid, liquid, gas) can coexist.

Runoff and Infiltration

• Runoff is the flow of water over the Earth's surface after precipitation.
• Runoff happens when the water encounters non-porous surfaces or saturated ground.
• Runoff can cause erosion and damage to ecosystems.
• Infiltration is water seeping into the soil.
• Infiltration rates depend on soil permeability and vegetation.

Water Conservation

• Water conservation involves strategies to save water.
• Sustainability is a key aspect of water conservation, balancing current needs with future availability.
• Water use types include consumptive (used and not returned), non-consumptive (used and returned), and sustainable (reused or recycled).
• Drip irrigation and specialized fountains are examples of sustainable water use.

Oceans and Seas

• Oceans and seas cover 71% of Earth's surface and contain ~96% of Earth's water.
• Oceans are large bodies of salt water between continents.
• Seas are smaller portions of oceans and are often connected to gulfs and oceans.
• Ocean water has high salinity and contains dissolved minerals and gases.
• Ocean temperature and density depend on salinity and temperature.

Tectonic Plates and Coastlines

• Earth's surface is divided into tectonic plates.
• Plate movement causes tectonic and seismic activity.
• Active continental margins have mountain ranges, oceanic trenches, and volcanic activity.
• Passive margins have little activity and often create flat landforms.
• Coastlines are formed on both passive and active margins.

Ocean Basins

• Ocean basins are depressions filled with water and diverse life.
• Ocean basins have several topographical features (continental shelves, slopes/rises, abyssal plains).
• Plate tectonic activity shapes ocean basins and their features.
• Features include oceanic ridges (sea floor spreading), abyssal hills, seamounts, and guyots.
• Trenches are formed by subduction.

Oceanic Ridge System

• The oceanic ridge system is a continuous underwater mountain chain.
• It's formed by tectonic plate movement, creating new ocean crust through seafloor spreading.
• Tectonic plates on Earth's lithosphere (crust and upper mantle) move on the asthenosphere, a warmer, deformable layer.
• Magma rising from the asthenosphere creates new crust.

Watersheds

• A watershed is a land area that drains water to a common outlet (river, lake, etc.).
• Drainage divides are boundaries between watersheds.
• Watersheds are important for water quality and flow.
• Non-point source pollution can affect downstream water quality.

Groundwater

• Groundwater seeps into subsurface rock formations.
• Factors that influence groundwater flow include porosity, permeability, and gravity (hydraulic gradient).
• Porosity determines water holding capacity, while permeability and gravity determine flow rate.