Explain the water cycle as a system driven by energy from the sun and the pull of gravity, naming each stage in order.
Water on Earth is always moving through a cycle, endlessly recycled, never used up. The sun's energy heats water in oceans, lakes, and rivers until it evaporates, turning from liquid into invisible water vapor gas that rises into the air. High in the sky, that vapor cools and condenses back into tiny liquid droplets, clustering together as clouds.
Once cloud droplets grow heavy enough, gravity pulls them down as precipitation: rain, snow, sleet, or hail. Some of that water soaks into the ground, infiltration, to become groundwater; some flows over the surface into streams and rivers, runoff, back toward the ocean; and some is taken up by plant roots and released back into the air through their leaves, transpiration. Two forces run this whole system: the sun's energy lifts water up, and gravity brings it back down.
Mastery looks like: They can name the water cycle stages in order and correctly identify whether the sun's energy or gravity is driving each stage.
Common stumbles: Thinking water is "used up" instead of recycled; forgetting transpiration and infiltration as real stages alongside the more famous ones.