Water Cycle - Oceans (6)

  • Discovering the Coriolis effect.
  • Experimenting with the ocean's movements.
  • convection
  • Coriolis
  • topography
  • wind
  • lab sheet
  • beakers
  • hot plate 
  • hot and cold salt water
  • food coloring
  • nail or pin
  • cardboard 

Students experiment with a model of the Coriolis effect.


This lab focuses on the movement of ocean water, which is a difficult principle to explain and understand.  Although wind, the movement of the Earth, and the differences between hot and cold water are the major factors that determine the direction of the ocean currents, topography and salinity also play a part.  This lab only looks at two factors:  the movement of the Earth and the differences between hot and cold water.

The differences between hot and cold water can cause movement.  Warm water rises and as it cools it gets heavier and sinks.  This motion is called a convection cell.  In the oceans there are many areas that have cold water, especially in the polar areas.  This cold water moves along the bottom of the oceans until there is an opportunity to rise, and when this occurs it is called upwelling.  The reasons for water rising are numerous.  Emphasize that there is motion caused by this temperature difference. 

The Coriolis Motion occurs as the Earth rotates, creating a movement in the ocean.  In the northern hemisphere water particles move to the right; in the southern hemisphere water particles move to the left.   This lab is meant to introduce the concepts, and not for the students to fully understand the complex mechanisms that are occurring.



Complete the demonstration using the hot and cold sea water as shown on the student's lab sheets.  Let the students record what is happening in their lab manual.  Point out that there are many factors that influence the movement of the water.  This "convection" caused by heat, is just one way.

  1. Place cardboard base on table top.
  2. Place piece of heavy construction paper in middle of base.
  3. Firmly place nail or pin through center of construction paper (being careful not to  allow nail head to come through).
  4. Fill medicine dropper with water.
  5. Turn nail upside down (head facing table) and spin like a top with the construction   paper spinning on top of heavy cardboard base.
  6. As the construction paper is spinning, the second partner will drop 1-3 drops of water   as close to the nail as possible.

Have the students change the direction of the spin and record what happens.  This demonstrates that a moving "sphere" deflects particles because of the motion.  This is the same thing on the Earth, except the water can't just "fly" off.

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