Growing Salt Crystals

How Do We Grow Salt Crystals?

Materials

  • Clean cup
  • Salt
  • Hot water
  • Spoon
  • Ruler
  • Fishing wire or thin thread
Procedure
  1. Pour hot water into the cup.
  2. Pour a spoonful of salt into the cup of water and stir.
  3. Repeat step 2 until salt starts appearing on the bottom of the cup after stirring.
  4. Tie a piece of fishing wire or thread onto the center of the ruler.
  5. Place the ruler over the top of the cup with the thread submerged in water.
  6. Leave everything in a room temperature environment for at least a day.
What to Observe
  • Observe the thread and see if anything appears on it.
Discussion

In a solution a solvent can only hold a certain amount of solute. This is called the solubility of a solution. In this experiment, the starting solution had reached its maximum solubility and was thus a saturated solution. However, as the temperature of the solution dropped, its solubility began to decrease and the solution couldn't hold the solute. As a result, the solution now became a supersaturated solution. The solution was forced to get rid of some of the solute and placed it on the nearest surface that could hold it. This was the thread that was submerged in the solution. As the temperature of the solution continued to drop and the volume of the solution also dropped as water evaporated from the solution, more salt accumulated on the thread forming the salt crystal.