Home School Life Journal From Preschool to High School

Home School Life Journal ........... Ceramics by Katie Bergenholtz
"Let us strive to make each moment beautiful."
Saint Francis DeSales

Ocean Currents, Part II: Salinity Currents

Salinity and temperature differences create masses of water with different densities. Gravity causes more dense water to sink below less dense water As a result, the less dense water rises. These factors create currents.
 For the next few experiments, we will explore how water of different salinity levels and of different temperatures react. Our first experiment will be with water of different salinity levels.

You will need:

  • 2 identical plastic bottles (about 12-16 ounces) with straight sides and threaded mouths (water bottles are good)
  • a tornado tube
  • a white dish towel
  • salt, Kosher preferred because it leaves the water more clear
  • food coloring (any color but yellow)
  • a yogurt or small container of sour cream lid with the rim cut off
  • room temperature water
  • a tablespoon

Fill two bottles with room temperature tap water. Fill one bottle to the very top and leave about an inch of space at the top of the second bottle. Add approximately  4 Tablespoons of salt (preferably Kosher salt as it leaves the water clear) and six drops of food coloring to the bottle with the space at the top and shake well. This is the salty water bottle. Screw a tornado tube tightly onto the salty water bottle. Finish filling the salty water bottle to the very top on the tornado tube with tap water.
Place a yogurt lid with the rim cut off over the top of the fresh water bottle. Press down firmly on the yogurt lid, invert the fresh water bottle and quickly place it over the opening of the tornado tube attached to the salty water bottle.
Carefully slide away the yogurt lid, allowing the two bottles to join together with the tornado tube between them. Screw the fresh water bottle tightly into the tornado tube.
Lay the bottles gently on their sides on a white dish towel to catch any drips. Have the one side of the dish towel bend up by attaching it to a box or a wall if one is close so that you can see the movement of the colored water. Try to disturb the bottles as little as possible. You may have to tighten the  tornado tube if you see more than a few drops leaking from either bottle.
Bend down to eye level and watch the movement of the water. At first the colored water will slowly seep into the clear water bottle and gather a little on the bottom of the tube. 
 If you continue to watch the bottles for at least 5 minutes, you will see that the bottles pretty evenly divide, with the colored water on the bottom and the clear water on the top.

 What do you think this tells you about when waters of different salinity levels come in contact with each other?
The water with the most salt and therefore the most density, will move to below the water with less salt and therefore less density. This movement can create a current.
If you like, you can sketch first the set up, labeling which bottle has fresh water and which has salty water, and then using colored pencils, show the movement of the colored water in the bottles and where it ends up.
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Originally posted Jan 21, 2011


  1. That is so cool. Now I want to go out and get a tornado tube even more. I was thinking about getting one this week to let the kids see how a tornado works.

  2. It's just so pretty! I love the shades of blue :)

  3. Very neat! I've never used a torndado tube, because we've managed to do the tornados without them - but that might be worth picking one up for.

  4. I just got a tornado tube recently but I didn't do any experiments besides just letting my daughter look at the tornado.

    This is a great idea, I will have to try it out!

    Ticia recommended that I come check out the activties that you did.

  5. We didn't have a tornado tube, so we just did this one in a jar. Still worked!


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