Introduction

It is a well known fact that the density of sea water varies from one place to another.

This is due to the differences in the concentration of salt in the sea. The density of sea water is greater, naturally, if more salt is dissolved in it.

Visualizing Different Salt Solution Densities

It is possible to illustrate how liquids of different densities float atop one another.

• Prepare a saturated solution of sodium chloride
• Divide the saturated solution into 3 cups (A, B and C) equally
• Cup A is a 100% saturated sodium chloride solution
• Add 50% water by volume to cup B to make up a 66% sodium chloride solution
• Add 100% water by colume to cup C to make up a 33% sodium chloride solution
• Prepare a cup D of pure water
• To cup A, add Blue food dye
• To cup B, add Orange food dye
• Leave cup C uncolored
• To cup D, add Cochinea Red food dye
• Prepare a clean empty glass test tube
• Use a plastic pipette and drip a few drops of blue dyed sodium chloride solution from cup A into the test tube
• Drip a few drops of orange dyed sodium chloride solution from cup B into the test tube
• Drip a few drops of clear sodium chloride solution from cup C into the test tube

  

• Finally, drip a few drops of Cochinea red dyed water from cup D into the test tube

  

• Observe the colors of the different layers separated by density :
  • Pure water floats on top
  • 33% salt solution
  • 66% salt solution
  • 100% salt solution, the densest, remains at the bottom

Last updated on 22 May 2013