Salt Water Purifier

This experiment demonstrates how salt water can be turned into fresh water using evaporation and condensation. It models the natural water cycle, showing how solar energy drives evaporation, and how condensation can collect purified water, leaving the salt behind.

1. Fill a large bowl with about 3 cm (1 inch) of warm water.
2. Add salt and stir until it dissolves, creating salt water similar to seawater.
3. Place a smaller empty bowl inside the large bowl, ensuring it sits above the salt water but is still surrounded by it.
4. Cover the large bowl tightly with plastic wrap and tape it around the edges to seal it.
5. Place a coin or small pebble in the center of the plastic wrap so that it dips slightly toward the middle above the small bowl.
6. Put the setup in a sunny spot (or under a warm lamp) for several hours.
7. Observe droplets forming on the underside of the plastic wrap and dripping into the smaller bowl.
8. After several hours, carefully remove the cover and taste a small amount of the collected water—it should be fresh.

Salt water purifier - The Experiment Archive:

Science Is Everywhere: Fresh Water from Salt Water — Desalination - Children's Discovery Museum of San Jose:

📄 Salt water purifier - Science Buddies: https://www.experimentarchive.com/experiments/salt-water-purifier/

• Use bowls of different sizes to test how surface area affects the amount of collected water.
• Try deeper or shallower salt water levels.
• Add food coloring to the salt water to visualize that only clear water evaporates.
• Conduct the experiment indoors with a lamp instead of sunlight.
• Add soil and grass to simulate natural evaporation from the ground (do not drink the water from this version).

• Do not drink the salt water or any unpurified samples.
• If adding soil or organic materials, do not consume the collected water.
• Handle glass bowls carefully to prevent breakage.
• Conduct the experiment in a stable, sunny, and safe area away from small children or pets.

• Why does the water that collects in the small bowl not taste salty? (Because when salt water evaporates, only water molecules turn into vapor; the salt and other impurities remain behind.)
• What role does the coin play on the plastic wrap? (It creates a low point where condensed water can drip into the center bowl.)
• How is this process similar to the natural water cycle? (It involves evaporation from a liquid surface, condensation on a cooler surface, and collection as precipitation.)
• What factors affect how quickly water evaporates? (Temperature, light intensity, surface area, and air movement.)
• How could this technique be useful in real life? (It models solar desalination, a method used in survival situations and water purification systems in arid regions.)