Evaporation

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Evaporation Linear Equations
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Abstract

• We are going to explore the relationship between
  surface area and evaporation.
• We will ask the question Is this relationship
  Linear, exponential, or erratic?
• We will also utilize some of the mathematical
  equations that help us understand our world.

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Materials

• You will need at least three glass containers of
  various sizes, each with a volume of at least one
  cup. For best results the containers should be
  roughly cylindrical.
• I recommend keeping a pad of paper and a writing
  utensil handy so you can log your observations.
• If the circumference of your vessels is unknown
  you will need a tape measure.
• In order to recreate the experiment exactly as it
  is displayed you will also need food coloring and
  an oven. If you dont have access to an oven use
  a window sill, and extend the timing of the
  sample from an hour, to two days.

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Procedure Step 1

• Preheat the oven to 400 degrees Fahrenheit and
  place you glass vessels on the center rack. We
  want to account for differences in the heat
  resistance by bringing them all up to the same
  temperature.

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Procedure Step 2

• Once the oven, and the vessels are preheated,
  remove them from the oven and fill each with
  exactly one cup of water.

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Procedure Step 3

• Place the vessels in the oven.

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Procedure Step 3

• Wait one hour and then remove the vessels from
  the oven, be careful that water is scalding hot!

While you wait it is a good idea to reflect on
your life, and grab a snack.
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Procedure Step 4

• Its time to come up with some results! Pour the
  content of each vessel into a measuring cup and
  write down the results.

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Procedure Step 5

• Now that we have our results, lets gather more
  information so that we can draw reasonable
  conclusions.
• Measure the diameter of each vessel.

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Math Time!

• The Diameters of my jars were 8, 10, and 12.
• Can you use these numbers to find the surface
  area? Here is a hint Surface area Pi (Radius
  Radius), but we dont have the radius yet.

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Algebra time

• You may recall that
• circumference 2 pi radius

Lets use algebra to flip this equation Circumfer
ence / 2 Pi
Radius
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Conclusion

• We are finally ready to draw some conclusions!
  Plug your radius numbers into the area of a
  circle equation, graph the results and see what
  happens.

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Good Work!

• If you followed the procedures correctly you
  should find that the equation graphed a roughly
  linear equation.
• Why not check your work? Divide the surface area
  by the amount of water evaporated. Depending on
  your elevation you probably got a number between
  25.5 and 33.5 for all of your containers.

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Going Further

• Can you tell me, based on the data you have
  collected, how much water would evaporate out of
  a glass cylinder if we re created the experiment
  with a 18 in. circumference jar?
• Can you find out why different elevations have
  different evaporation rates?