The Invisible Ink Task

You are a lab technician for a toy company. Your company has developed and patented a nontoxic form of invisible ink. When you write on paper with the liquid and let it dry, the writing becomes invisible (it becomes visible, again, when you apply another chemical to it). Only you and your team of scientists know that the ink is actually a solution of cobalt chloride in water. Cobalt chloride is expensive. Water is less expensive, and the lab has plenty of water.

Your Challenge

Prepare a batch of 0.7 L (liters) of cobalt chloride solution for your company’s next shipment. The concentration of the solution should be between 1.995 and 2.005 mol/L.

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Simulation Quick Tour

  1. Add Water
    Pull handle to the right
  2. Add Solid
    Shake left & right
  3. Add Solution
    Select and squeeze top of pipette
  4. Select Solute
    Click drop down & select
  5. Measure Concentration
    Drag meter probe into liquid
  6. Drain Water
    Click on handle & pull right
  7. Remove Solute
    Click on button
  8. Evaporate
    Drag slider to the right
  9. Reset
    Click on arrow button

Your Challenge

Prepare a batch of 0.7L(liters) of Cobalt Chloride solution.

The concentration of the solution should be between 1.995 and 2.0005 mol L.

Make Note

  • Try not to waste cobalt clhoride - it's expensive!
  • There is plenty of water available - it's cheap!

Summary:

metacog automatically scores open-ended learning objects (such as educational games and simulations) based on a rubric. Publishers and content developers can develop rich learning objects that offer actionable feedback without the limitations of multiple-choice assessments.

Visit phet.metacog.com/InvisibleInk and perform the task as many times as you'd like

Explore the Full Lesson At: phet.metacog.com/InvisibleInk2