Water on Earth

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Molecule Noun

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[mol-uh-kyool]

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Molecule

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The smallest electrically neutral unit of a substance, consisting of two or more atoms held together by chemical bonds.

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Example: This image shows a water molecule is made of two hydrogen atoms and one oxygen atom chemically bonded together, representing the term 'Molecule'.

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Atom Noun

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[at-uhm]

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Atom

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The basic unit of a chemical element, consisting of a dense central nucleus surrounded by a cloud of electrons.

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Example: This diagram shows an oxygen atom, a basic unit of matter, with a central nucleus (protons and neutrons) and electrons orbiting in shells.

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Water Vapor Noun

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[waw-ter vey-per]

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Water Vapor

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The gaseous phase of water, which is produced from the evaporation or boiling of liquid water and is invisible.

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Example: Heating liquid water in the kettle causes it to boil and change into a gas, which is visible as steam (water vapor).

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Hydrosphere Noun

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[hahy-droh-sfeer]

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Hydrosphere

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The combined mass of water found on, under, and above the surface of a planet, minor planet, or natural satellite.

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Example: This diagram shows the water cycle, illustrating how water moves through the hydrosphere via evaporation, condensation, and precipitation, connecting all of Earth's water.

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Saline water Noun

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[sey-leen waw-ter]

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Saline water

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Water that contains a significant concentration of dissolved salts, with a salinity greater than that of freshwater.

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Example: This diagram shows that saline water contains salt. When heated, only the water evaporates, leaving the salt behind. The water vapor can then be cooled to produce freshwater.

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Freshwater Noun

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[fresh-waw-ter]

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Freshwater

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Naturally occurring water on Earth's surface with low concentrations of dissolved salts, essential for most terrestrial life.

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Example: This diagram shows a cross-section of a freshwater body, like a lake, and labels its different depth zones where various organisms live.

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Reservoir Noun

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[rez-er-vwahr]

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Reservoir

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A natural or artificial location where a significant amount of water is collected and stored for various uses.

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Example: A dam blocks a river to create a large, artificial lake called a reservoir, which stores water for human use.

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Ice Cap Noun

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[ahys kap]

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Ice Cap

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A large, thick sheet of ice and snow that covers a vast area of land, such as in polar regions.

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Example: This map shows the thickness of the Greenland ice cap. The colors indicate that the ice is a massive dome, over 3000 meters thick at its center.

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Glacier Noun

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[gley-sher]

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Glacier

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A large, persistent body of dense ice that is constantly moving under its own weight over a land surface.

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Example: This diagram shows a glacier is a large body of dense ice that forms from accumulated snow on mountains and moves slowly downhill under its own weight.

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Groundwater Noun

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[ground-waw-ter]

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Groundwater

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Water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations.

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Example: This diagram shows how rain infiltrates the ground, seeping through soil and collecting in a porous underground layer called an aquifer, forming groundwater.