In the water cycle, which process leaves salt behind as water rises into the air?
AnswerEvaporation
When seawater evaporates, the salt stays behind, so rain falls as fresh water.
Nature · Facts & stats
Clearwater facts & stats
7 fact-checked facts about clear water, each with the reason behind it. 5 more are in today's round and join this page after it closes.
The basics
Which of these animals cleans water by filtering out tiny particles as it feeds?
AnswerOysters
Oysters are filter feeders that strain plankton and particles from the water they pump.
Going deeper
Why does very clear, deep water look blue?
AnswerWater absorbs red light more strongly than blue
Water molecules absorb red wavelengths, so the light that travels back to our eyes is bluish.
In water treatment, what is the step where tiny particles clump together to settle out?
AnswerCoagulation and flocculation
Coagulants make particles stick into larger flocs that sink or are filtered out.
What is an algal bloom?
AnswerA rapid increase of algae that can cloud water
Blooms happen when algae multiply quickly, turning water green and murky.
Expert level
What is it called when excess nutrients like nitrogen and phosphorus cause algae overgrowth?
AnswerEutrophication
Eutrophication is nutrient enrichment of water that fuels algae growth and lowers clarity.
How does ultraviolet (UV) light help treat drinking water?
AnswerIt damages the DNA of microorganisms
UV light disrupts the genetic material of bacteria and viruses so they cannot reproduce.
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