Roman Numerals, Invisible Ink and Chemical Reactions

The best part about Roman Numerals? Its like a code.  Codes are cool. You know what else is cool?  Invisible ink.  Even better…chemical reactions.

It all began with a math puzzle.  During snack, each Magical Mind was give a number, written out.  For example, nine hundred and nine.  Their task was to figure out how to write the number with digits. For example, 909.

There were four numbers, and after snack I asked the kids with the same numbers to form teams.  They worked together to write their numbers, and then I gave them a challenge.  “Work with your team to write the Roman Numeral for your number.”

Now for the invisible ink.  I wet a paintbrush in some brown liquid and painted a white piece of paper.  The liquid turned the paper a shade of bluish-purple, except where I had secretly written a Roman Numeral.

Each team received a small vial of “mystery liquid” to write/paint their Roman Numerals.  They worked with each other to share materials and write their numbers.

After setting our hidden messages aside to dry, we took a short break to clear our minds. I needed them to shift their minds from thinking mathematically to thinking scientifically.

The invisible ink works because of a chemical reaction.  In order to help the Magical Minds understand what a chemical reaction is, I invited them to participate in a science experiment with Alka-Seltzer and baking soda.

Each team got a set of four test tubes filled with clear liquid.  I informed them there were only two different kinds of liquids and asked them to use their senses to determine what the liquids were.

With some investigation the Magical Minds quickly discovered the test tubes held either water (“pool water” was the most common response) or vinegar.

Each team was given a small piece of Alka-Seltzer and instructed to place half of the tablet in each liquid and observe the reaction, if there is one. I let them know that if they see a change in the liquid or a change in the Alka-Seltzer they would know it was a chemical reaction.  After watching the bubbling and fizzing, the kids agreed that the Alka-Seltzer reacted with both liquids, but it had a stronger reaction in the water.

Next, each team was given a small vial with baking soda.  I asked them to test 1/8 tsp in each remaining test tubes and look for chemical reactions.  As you may have predicted the Magical Minds detected no chemical reaction when they added baking soda to water, but were giggly and excited when they witnessed the foaming reaction between baking soda and vinegar.

Armed with a burgeoning understanding of chemical reactions, the Magical Minds returned to the invisible ink.  I demonstrated how I added iodine to water to create the brown-ish liquid.  “Paint the iodine water on top of the invisible ink and look for a chemical reaction.”

What do you think?  Does the iodine react with the lemon juice?


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