Try This at Home

Here is a little experiment you can do at home or in the classroom to see for yourself how fresh water floats on salt water.

Materials list:

  1. 1 Five gallon bucket
  2. 1 Four inch diameter plastic pipe 18 inches long
  3. 5 small water balloons
  4. 1 Quart size measurer
  5. Seven pounds of salt
  6. 6. A large baby syringe or turkey baster
  7. Small plastic bag
  8. Small ½ cup measuring cup

Step 1:
Fill bucket with approximately four gallons of water. Add the seven pounds of salt, stir and mix well. Using ½ cup, measure equal amounts of saltwater (from your bucket) and freshwater and pour them into the quart size measurer and mix well. Now using the baby syringe, fill the small balloons with the 50/50 mix of salt and freshwater. The balloons should be about 2 inches in diameter or smaller and all the air must be removed by squeezing it out before tying it shut. Wash the quart measurer out and fill with fresh water.

Step 2:
Place the pipe in the bucket holding it in place with one end above the surface of the water and the other end about an inch above the bottom of the bucket. Now place your balloons inside the pipe and they should float at the surface [it is not necessary to use ALL of the balloons]. Next, place the small plastic bag on top of the balloons. This is to keep the fresh water from splashing below the surface as it is poured in. With bag in place, use the small measurer to add freshwater to the top of the pipe by pouring it onto the plastic bag diffuser. Once the balloons are covered with freshwater, they will begin floating lower in the pipe. The more freshwater you add to the pipe, the lower the balloons will float. The plastic bag can be removed as soon as the balloons leave the surface. You can add the quart of freshwater and the balloons will be several inches under the surface. You can use the small ½-cup measurer to remove the freshwater by dipping it into the water and pouring it back in the quart measurer until the balloons come back to the surface. This is how the physics of this whole idea work, and yes, it is that simple.