======Evaporating Seawater======


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**Alternative titles:** Salt from Seawater at Home
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====Summary====                   
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====Procedure====  
  - Set a shallow, clear bowl on a stable surface. Pour in warm water (not boiling).
  - Stir in table salt a spoonful at a time until some grains no longer dissolve (a sign of saturation). Let undissolved grains settle.
  - (Optional) Pour the clear solution into a clean dish, leaving any grit behind.
  - Use a dry-erase marker to draw a waterline on the outside of the dish.
  - Place the dish somewhere warm and undisturbed with good airflow (away from pets and small children). Do not cover it.
  - Observe daily: record the water level by adding a new mark and note any salt deposits forming on the sides and bottom.
  - After about a week (or when most water has evaporated), examine the salt crystals that have formed. Gently scrape a few onto dark paper to observe shapes.



====Links==== 
To Separate a Saltwater Mixture by Evaporation - Simple Science and Maths: 
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Science experiment: Separating mixture by EVAPORATION - argenicz: 
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📄 A Super Simple Salt Water Evaporation Experiment - Homeschool by Joanna: [[https://joannacinnamon.com/a-super-simple-salt-water-evaporation-experiment/]]\\


====Variations====
  * Run two dishes: one uncovered at room temperature and one loosely covered, and compare evaporation rate and crystal size.
  * Compare shallow wide dishes vs deeper narrow cups to test how surface area affects evaporation time.
  * Start one dish with a few grains of dry salt (“seeds”) and another with none to see how seeding changes where crystals form first.
  * Try different salts (table, kosher, sea salt) and note differences in crystal clarity and shape.
  * Add a simple measurement: weigh the empty dry dish, then the dish plus dry crystals at the end to estimate salt recovered; graph waterline height vs day.
  * Evaporate water in a cooking pot on the stove.


====Safety Precautions====
  * Adult supervision required when using warm water and glass/ceramic dishes.
  * Do not taste the solutions or crystals prepared for the experiment; label the dish “Do Not Eat.”
  * Keep setup out of reach of young children and pets; clean spills promptly—saltwater can damage some surfaces.
  * If you heat water on a stove, use oven mitts and place hot containers on heat-safe surfaces.





====Questions to Consider====
  * Why doesn’t the salt evaporate with the water? (sodium chloride is nonvolatile at room temperature; only the water molecules evaporate.)
  * Why do crystals form along the rim as the waterline drops? (evaporation at the contact line leaves salt behind; capillary action draws solution up the sides.)
  * How do temperature, airflow, and surface area change the evaporation rate? (warmer air, more airflow, and larger surface area speed evaporation.)
  * What evidence shows the solution became supersaturated before crystals formed? (clear solution at first, then sudden appearance/growth of solid as water volume decreased.)
  * If you wanted to recover fresh water from salt water, what extra step would you need? (collect and condense the water vapor—distillation—rather than just evaporating it.)