Study Guide

Quick meanings for every word. Pair Tier 3 words with pictures to support newcomers.

Word	Meaning
Pollution	Harmful substances introduced into air, water, or land that can damage the health of people, animals, or plants.
Precipitation	Water that falls from clouds as rain, snow, sleet, or hail.
Temperature	A measure of how hot or cold matter is, related to the average kinetic energy of its particles.
Water	The substance H₂O, which can exist as solid ice, liquid, or gas.
Acid / Acidic	Describes a water-based solution with a pH below the neutral value, which is 7 at 25 °C.
Alkaline	Describes a water-based solution with a pH above the neutral value, which is 7 at 25 °C.
Aquifer	A body of rock or sediment that stores groundwater and lets enough of it flow to supply wells or springs.
Atmosphere	The layers of gases that surround Earth.
Base / Basic	Describes a water-based solution with a pH above the neutral value, which is 7 at 25 °C.
Condensation	A gas changing into a liquid, often as it cools.
Evaporation	A liquid changing into gas at its surface; this can happen below its boiling point.
Ground	The solid surface of land that people and animals walk on.
Hydrologic Cycle	The nonstop movement of water between the land, the ocean, the air, and living things. Also called the water cycle.
Hydropower	Electricity generated using the force of moving or falling water.
Hydrosphere	All of the water on Earth: oceans, lakes, rivers, ice, ground water, and water vapor.
Infiltration	Water soaking down into the ground.
Neutral	Describes a water-based solution with equal hydrogen- and hydroxide-ion activities; its pH is 7 at 25 °C.
Permeability	How easily a fluid can move through connected spaces in a material.
Permeable	Letting water or air pass through.
pH Level	A number describing how acidic or basic a water-based solution is; lower values indicate greater acidity.
Porosity	The fraction of a material’s total volume made up of open spaces.
Puddling	Water collecting and standing on the surface instead of soaking into the ground.
Runoff	Water that flows over the land surface instead of soaking in.
Salinity	How much salt is dissolved in water.
Surface	The outermost, top layer of something, such as land or water.
Sublimation	A solid changing straight into a gas without melting first.
Watershed	All the land that drains into one river or lake.
Water Quality	The physical, chemical, and biological condition of water, considered in relation to a use or the needs of living things.