Twelfth Grade · Science · week 7

The water cycle and the carbon cycle

Trace the major processes and reservoirs of the water cycle and the carbon cycle, and distinguish the fast and slow parts of the carbon cycle.

The water cycle moves water between reservoirs through a handful of named processes: evaporation (liquid water into vapor, mostly from oceans), transpiration (water vapor released by plants), condensation (vapor into clouds), precipitation (rain or snow falling), infiltration (water soaking into soil and groundwater), and runoff (water flowing over land into streams and rivers). About 97% of all water on Earth is saline ocean water, so this whole cycle is really about constantly recycling a small, precious freshwater share.

The carbon cycle has a fast loop and a slow loop. The fast loop exchanges carbon between the atmosphere and living things in months to years: plants pull CO2 out of the air through photosynthesis, and respiration (by plants, animals, and decomposers) puts it back. The slow loop moves carbon through rock, ocean sediment, and fossil fuel formation over millions of years -- carbon buried in ancient swamps and sea life can be locked away as coal, oil, or limestone for geologic ages before anything releases it again.

📋 For the teacher
Teach it (10–15 min):
  • Trace an imaginary raindrop out loud together from the ocean to your kitchen faucet and back -- naming each process keeps the vocabulary from feeling abstract.
  • Point out that a lump of coal is essentially very old, compressed carbon that has been "on pause" in the slow cycle for millions of years.
  • Ask your student which loop -- fast or slow -- humans have most dramatically sped up by burning fossil fuels (this previews next week).
  • Field investigation, watershed walk: after the next rain, follow where water runs from your street or yard -- toward a curb, storm drain, ditch, or stream -- as far as you can observe or reasonably trace, to identify the nearest step in your local watershed.
Talk about it:
  • Which water cycle process do you think is easiest to observe directly where you live?
  • Why does it matter, for climate questions, whether carbon is moving through the fast loop or the slow loop?
  • What is one everyday object made from "slow loop" carbon that took millions of years to form?

Mastery looks like: They can name the correct water cycle process for a described transition and correctly classify a carbon movement as part of the fast loop or the slow loop.

Common stumbles: Confusing weather with the water cycle; assuming all carbon moves at the same speed through the cycle.

Homework for this lessonType it, write it with a stylus, or print it for pencil & paper.open →
Records attendance + 15 min of Science for this learner.
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