Easy Blue Color Change Demo

Color Change Demo with Household Chemicals

Many copper complexes are bright blue.
The vivid blue of this solution results from an amino-copper complex produced from mixing copper sulfate with dilute ammonia. Anne Helmenstine

You don't need a chemistry lab to perform a dramatic color change chemistry demonstration. Make a pale blue solution. Add another chemical and watch the solution form a precipitate and turn milky sky blue. Continue adding the color and watch swirls of vivid blue form, until finally, the entire solution turns deep translucent blue.

Chem Demo Materials

You only need water and two household chemicals for this project:

  • hot tap water
  • copper sulfate
  • household ammonia

I used Root Kill™, which states on its label it is copper sulfate. Some pool treatments and algicides consist of copper sulfate, but read the ingredient list to make certain. Ammonia is sold as a common household cleaner. If you can't find pure dilute ammonia, try a glass cleaner that contains ammonia.

Perform the Color Change Demo

  1. Dissolve a spoonful of copper sulfate in a cup of hot water. The proportions are not critical, but you want a high enough concentration of copper sulfate to get a blue color.
  2. Stir in a small amount of ammonia. See the swirls of milky pale blue? The blue solid will settle out of solution if you allow it to sit undisturbed.
  3. Adding more ammonia will start to turn the solution deep blue -- much brighter than the original copper sulfate solution. When the reaction goes to completion you'll end up with a translucent blue liquid. You can a video of this reaction at YouTube to see what to expect.

What Happened?

Ammonia and copper sulfate initially react to precipitate copper hydroxide. Additional ammonia dissolves the copper hydroxide to form a vivid blue amino-copper complex. The cuprammonium solution could be used to dissolve cellulose as part of one method of producing Rayon.

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