The Hydrosphere

Unit Review Sheet

Facts and Definitions

Lesson 1: The Hydrosphere and the Nature of Water

• The hydrosphere is the Earth system that includes all the water on Earth, including oceans, lakes, rivers, groundwater, ice, and water in the atmosphere.
• Water is made of molecules, and each water molecule is made of two hydrogen atoms and one oxygen atom (H₂O).
• Water molecules are always moving and are constantly interacting with other water molecules.
• Polarity means that a molecule has a slightly positive end and a slightly negative end.
• Water is a polar molecule, which means its positive and negative ends affect how it interacts with other molecules.
• Cohesion is the attraction between molecules of the same substance, such as water molecules sticking to each other.
• Adhesion is the attraction between molecules of different substances, such as water sticking to glass.
• Surface tension is a property of water that allows its surface to resist being broken or stretched.
• Surface tension is caused by cohesion, which pulls water molecules together at the surface.

Lesson 2: Density, Salinity, and Water Behavior

• The density of a material is its mass per unit volume. Density is mass divided by volume ($D=\frac{M}{V}$).
• Substances have different densities depending on their content. For example, tap water is less dense than salt water.
• Mass and weight are not the same - mass measures the amount of matter in an object, and weight measures how heavy the object is.
• Salinity is a measure of how much salt is in water. Salinity and temperature influence density.
• Differences in salinity and density affect how water moves and mixes.

Lesson 3: Oceans and Ocean Currents

• A current is the steady flow of water in a particular direction, often caused by differences in temperature, salinity, or wind.
• Thermohaline circulation is the deep, slow-moving system of currents in the ocean.
• Upwelling is the process in which winds blow the surface water away, and deep, cold, nutrient-rich water rises to the top.
• Density plays a significant role in the movement of the oceans' waters. Variations in density due to variations in temperature and salinity drive a global pattern of interconnected ocean currents.
• The ocean exerts a major influence on weather and climate by absorbing energy from the sun, releasing it over time, and globally redistributing it through ocean currents.
• The complex patterns of the changes and the movement of water in the atmosphere, determined by winds, landforms, and ocean temperatures and currents, are major determinants of local weather patterns.

Lesson 4: Freshwater and Groundwater

• Groundwater is water contained in the open spaces (pores) found in soil and/or rock.
• A permeable layer is a layer through which water flows or passes easily (for example, limestone).
• An impermeable layer is a layer through which water does not flow or pass (for example, granite).
• An aquifer is an underground layer of rock or soil that stores and holds groundwater between particles.
• The zone of saturation is the zone found in an aquifer that has all the pores filled with water.
• The water table is the top surface of the zone of saturation. It may be above or under ground.
• The zone of aeration is an area of an aquifer where the pores are partially filled with water and partially filled with air.
• Runoff is the water from rain or melting snow that flows over the land and into rivers, lakes, or oceans.
• Growth of living organisms like animals and humans and population increases are limited by access to water.
• Freshwater moves through the ground and is stored in underground reservoirs that support ecosystems and human life.

Lesson 5: Aquatic Ecosystems

• The biosphere is made up of all the ecosystems found on Earth.
• An estuary is a coastal area where freshwater from rivers and streams blends with saltwater from the ocean, creating a partially enclosed water body.
• Brackish water is water that is a mixture of freshwater and saltwater, usually found in places like estuaries where rivers meet the ocean.
• Thousands of species of birds, mammals, fish, and other wildlife rely on estuarine habitats for living, feeding, and reproducing.
• Biodiversity describes the variety of species found in an aquatic ecosystem.
• The integrity of an ecosystem's biodiversity is used as a measure of its health.
• Aquatic ecosystems depend on water conditions and the interactions of living organisms within them.

Lesson 6: The Water Cycle

• The water cycle is the continuous movement of water on Earth as it changes form—evaporating into vapor, forming clouds, and falling back as rain or snow
• Evaporation is the process by which liquid water changes into water vapor and enters the atmosphere.
• Condensation is the process by which water vapor (gas) cools and changes back into liquid water, forming clouds.
• Precipitation is any form of water that falls from clouds to Earth, such as rain, snow, sleet, or hail.
• Transpiration is the process where water is taken in by plant roots, transported to its leaves, and released back into the atmosphere
• Infiltration is the process by which water soaks into the ground and enters the soil.
• Percolation is the process by which water moves downward through soil and small spaces in rock due to gravity

Lesson 7: Weathering and Erosion

• Water movements cause weathering and erosion, which change the land's surface features.
• Mechanical weathering is the process of breaking rocks into smaller pieces without changing what the rock is made of. This can happen when water freezes in cracks, roots grow into rocks, or rocks bump into each other.
• Chemical weathering is the process of breaking down rocks by changing their chemical makeup. This happens when water, acids, or oxygen react with minerals in the rock, forming new substances.
• Erosion is the process by which natural forces like wind, water, glaciers, and gravity move sediments from one place to another.
• Deposition is the process where moving water, wind, or ice drops sediments in a new location. This happens when the movement slows down and can no longer carry the materials.
• Sediments are small pieces of rock, soil, and organic material that are carried by natural forces like water, wind, ice, or gravity.

Lesson 8: Water Pollution

• Agricultural runoff is water that flows over farmland and carries fertilizers, pesticides, and waste into nearby rivers, lakes, and oceans.
• Hypoxia is a lack of oxygen.
• Eutrophication is when excess nutrients in water cause rapid algae growth, leading to oxygen depletion and harm to aquatic life.
• As human populations grow and resource consumption increases, the negative effects on Earth's environment, including those from farming, typically rise—unless activities and technologies are carefully engineered to reduce harm.
• Ecosystems are dynamic in nature; disruptions to any physical or biological component can lead to shifts in all its populations.
• Oxygen is a key factor in the chemistry and biology of coastal waters, and its concentration indicates water quality, with higher levels supporting thriving ecosystems.
• Nitrogen is essential for photosynthesis in marine plants, but it must first be converted into usable forms like nitrate or ammonia before plants can absorb it.

Lesson 9: Water Treatment, Conservation, and Clean Water

• Filtration is the process of removing solid particles from a liquid by passing it through a material that traps the solids.
• Sedimentation is the process in which heavier particles settle to the bottom of a liquid due to gravity.
• Treatment is the process of making water safe to use by removing harmful substances and organisms.
• Conservation is the careful use and protection of natural resources to prevent waste and ensure they are available in the future.
• Chlorination is the process of adding chlorine to water to kill harmful bacteria and other microorganisms.
• Wastewater is water that has been used and contains waste materials from homes, industries, or businesses.
• Stewardship is the responsible care and management of natural resources, including protecting and preserving water for future use.

Final Project: Local Water Investigation

• [none]