Color Change Chemistry

Color Change Chemistry

Change a clear liquid pink, then back to clear again in this impressive experiment. It may seem like magic, but it’s actually the science of PH.

Things you’ll need: a beaker, a graduated cylinder, test tube holder, 3 test tubes, pipet, phenolphthalein, sodium carbonate, vinegar, and water.20170613_163519

  1. Fill the beaker halfway with water, and set the test tubes in the holder. I’ll refer to them in order as test tube 1, 2, and 3.20170613_163623
  2. Use a spoon to put a little bit of sodium carbonate in test tube 1.Use the pipet to add a few drops of water from the beaker. Swirl the test tube around to dissolve.20170613_164027
  3. In test tube 2, put two drops of phenolphthalein.20170613_164150
  4. Use the graduated cylinder to add 10 ml of vinegar to test tube 3.
  5. Carefully fill the first two test tubes with water from the beaker. Then, all at once, pour the contents of test tube 1 and 2  back into the beaker. The water will turn pink.20170613_164252
  6. Now pour the contents of test tube 3 into the beaker. the liquid will now be clear again. 

Phenolphthalein is a PH indicator that changes color when mixed with a base  (like sodium carbonate) but stays clear when mixed with an acid (like vinegar). In step 5, the phenolphthalein reacted to the basic sodium carbonate and turned the solution pink. To change it back to clear, you added acidic vinegar, neutralizing the basic sodium carbonate.

Learn more about phenolphthalein at this post: Invisible ink

10 Replies to “Color Change Chemistry”

  1. Nicely demonstrated. 🙂 I used to use phenolphthalein when I did titrations in the lab. The fun thing is that just one drop can change the colour, when the solution is balanced just right.

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