If a basin loses half its water by evaporation while salt remains dissolved, its concentration doubles in this ideal example. Adding fresh water reverses that dilution relationship without creating or destroying salt. The model excludes overflow, crystals forming, additional ions and exchanges with an open ocean.
Water and oceans · Discover & try
Why does evaporation leave the ocean’s salt behind?
Reading level 4 of 5 · FluentChange
Word help
Salinity
The concentration of dissolved salts in water.
Dilution
A reduction in concentration when more solvent is added.
Dissolved
Mixed into a liquid at the molecular or ionic scale.
Watch · Try · Explain
See how it works
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Ideal well-mixed basin using grams per litre; no crystallization, overflow or full ocean chemistry.
What to look for
- Keep salt mass fixed while water changes.
- Compare evaporation with fresh-water addition.
- Read grams per litre separately from total grams.
Explain what you noticed
A new covered bowl contains 20 grams of dissolved salt in 2 litres of water. It gains 2 litres of fresh water without losing salt. What happens?
Keep this idea: Evaporation removes water while leaving most dissolved salt; rain adds fresh water and dilutes it.
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