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Pie-Pan Convection
Grade Levels
6th Grade , 7th Grade , 8th Grade
Related Academic Standards
Commonwealth of Pennsylvania Standards and Anchors
3.2.3.A3 Demonstrate how heating and cooling may cause changes in the properties of materials including phase changes.
3.2.3.B2
Explore energy’s ability to cause motion or create change.
Explore how energy can be found in moving objects, light, sound, and heat.
3.2.3.B3 Explore temperature changes that result from the addition or removal of heat.
3.2.4.B1 Explain how an object’s change in motion can be observed and measured.
3.2.6.B3
Give examples of how heat moves in predictable ways, normally flowing from warmer objects to cooler ones until they reach the same temperature.
Explain the effect of heat on particle motion by describing what happens to particles during a phase change.
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Content Provider
© Exploratorium
To Do and Notice
Let your soap solution settle for a minute (so that there is very little fluid motion). Plug in the hot plate and place it on a low setting. Your hot plate should be hot
enough within a few seconds. Place the pie-pan on top of the heating element.
Watch what happens, but don't let the pan and liquid get too hot. The stearate molecules will break down and the pearly/metallic luster will vanish from the solution.
After awhile remove the pan from the heating unit and place it on a flat cool surface. Wait and watch what happens now.
Description
By heating a solution of soap, water and food coloring, fluid motion can be visualized.
Materials
• Aluminum pie-pan
• Hot plate
• Dye --- any color
• Tap water
• Bottle of liquid hand soap or shampoo that has a pearly or metallic appearance. Look for the following ingredient on the label: glycol stearate, glycol
distearate or glycerol stearate. Good brands to try are Softsoap® and Walgreen's Liquid Soap.
Duration
20 - 25 minutes
Assembly
Fill the pie-pan between 1/2 to 3/4 full with tap water and squeeze in about 2 tablespoons of hand soap. Gently stir the soap and water; try not to create bubbles. Stir
until the soap is mixed throughout the solution. To see convection currents and fluid flow more easily, darken the soapy solution by adding a few drops of dye to the
mixture.
Websites
Exploratorium - Science Activities
What's Going On?
The soap solution at the bottom of the pan heats-up and becomes less dense. This lighter liquid rises in localized columns. When the warm fluid reaches the surface,
it cools, becomes heavier and sinks. The region where the fluid rises and sinks is called a convection cell.
When on the heater, convection cells rise directly above the heating element. This allows you to see the shape of the hot plate coil below. When on the flat cool
surface, the convection process slows. This allows convection cells to widen and become extremely well defined.
Etcetera
Try doing this without a hot plate. Place the soapy solution on some one's warm hand and watch what happens.
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