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MIDDLE SCHOOL EXPERIMENT: What's Your Current Direction?


Because the atmosphere is a fluid it behaves just like other fluids. Its behavior is influenced by heat, density, and viscosity. As these factors are applied to the moist air, motion known as convection currents form causing the air to circulate and clouds to form.

National Science Education Standards Addressed:

  • PROPERTIES and Changes of Properties in MATTER/MOTIONS and Forces/TRANSFER of ENERGY
  • Understanding About SCIENCE and TECHNOLOGY/Populations, RESOURCES, and ENVIRONMENTS

Materials Needed:

  • 2 - 500 ml beakers
  • tap water
  • 35g of salt
  • balance
  • plastic spoon
  • cup-shaped coffee filter
  • red and blue food coloring
  • one clear container
  • one laminated file folder
  • neutral color clay
  • permanent marker
  • ruler


Use a permanent marker to trace a line on the outside of the container dividing it vertically in half. Roll a piece of clay into a long, 20 mm diameter rope . Carefully place the rope on the inside of the jar along the line dividing the container in half. Press the edges firmly in place leaving 10 mm raised along the center of the rope. Cut the laminated folder to the width of the container. Fit the folder into the center of the plastic box along the clay rope. Press the folder firmly into the clay to form a waterproof seal. Place the cup-shaped coffee filter on the balance and weigh out 35g of salt. Fill one 500 ml beaker with tap water, add the salt, stir until dissolved, add a few drops of red food coloring and stir. Fill the other beaker with 500 ml of tap water, add blue food coloring and stir. Do not make the solutions too dark. At the same time, pour a beaker of red liquid into one side of the container and a beaker of blue liquid into the other side of the container. Have one group member hold the box down. Carefully, but quickly remove the card by pulling it straight up and away from the box. Observe the results.


  • What happens to the movement in the solutions when the card is removed? Why? What would happen if the card is removed slowly? Why? Did the clay rope prevent the fluids from mixing too soon? Why or why not? What other substances might be used instead of clay?
  • What difference did the color make when observing the movement in the solutions? Why? Why were the colors red and blue selected instead of another color combination? Which other colors might work? Why?
  • What might be the affect on your observations if no color were added to the solutions and the experiment was performed in the identical way? What purpose does the food coloring serve in the experiment?
  • How do the results of your experiment relate to cloud formation and circulation in the atmosphere?


  • Design an experiment to test various colors. What would happen if the color yellow was substituted for the color red? Why? Does the color change make any significant difference in the result of the experiment? Why or why not? Which color combinations work best to demonstrate convection currents during the mixing of the water? What would happen to the experiment if you added color to only one of the solutions? What would happen if the color was added to the remaining solution instead of the one you elected to leave colorless? Use charts, illustrations, and wall murals to present your results.
  • Design an experiment to test what would happen if you used two beakers of plain water or two beakers of salt water. Develop a list of other substances you could use instead of salt. Select any three substances and test them. How did the results of the experiment differ from the original experiment? Why? Which other substance works best? Why? Write a newspaper article describing your results. Include 2-3 pictures with your article.
  • How would the results of the experiment differ if less salt was used? How would the results of the experiment differ if more salt was used? How many grams of salt did it take until no more salt could be dissolved in the beaker and the solution became saturated ? Why can only a specific amount of salt be dissolved in the beaker? How could you make more salt dissolve in the beaker? What is a supersaturated solution? When, how, and why would you use a supersaturated solution?