How to Turn a Glass of Water With Red Dye Back Into Clear Water

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Some chemistry experiments look more dramatic than others. Turning a glass of apparently pure water into “wine” and back again should certainly impress your audience. It also makes a good visual demonstration of a pH indicator, and happens to be one of the most straightforward experiments to set up, whether you need a crowd-pleaser for a molecular chemistry project or just want a simple magic trick.

    Place a small amount of sodium hydroxide in the first glass and a little phenolphthalein in the second. In the third, add a weak acid, such as vinegar. Using differently shaped glasses ensures that you will not get them confused.

    Fill a jug with water when you are demonstrating this experiment to others. As this is plain water, you can let your audience taste it.

    Pour water into the first glass and stir. This is now no longer pure water but a mildly alkaline solution.

    Pour the contents of the first glass into the second and stir. Watch as the mixture changes color, because phenolphthalein is a pH indicator that turns red in alkaline solutions.

    Pour the red liquid into the third glass and stir once more. The acid neutralizes the solution, which should now become clear again.

    Tips

    • Before demonstrating this experiment, whether as part of a presentation or a magic trick, experiment to see what amounts of the chemicals produce the best results. Start with a tiny amount for each stage and add more until you achieve the desired effect.

      As an alternative to using acid to make the color disappear, try blowing through a straw into the solution. The carbon dioxide you exhale reacts with the water to produce carbonic acid, which ought to have a similar effect. This happens to make the experiment useful for projects on ocean acidification.

    Warnings

    • Don’t drink the mixture afterward or let anybody else try. Although they won’t kill you, these chemicals, with the exception of the vinegar, are not food substances and may make you feel ill. If you really want a genuine red drink and already have fairly good stage-magician skills -- be honest -- prepare a fourth glass with red juice or soda and keep it hidden. Once you have done the “water” into “wine” part, distract the audience and swap the glasses. Then offer somebody the juice to drink. Just be completely sure you are offering the right glass.

      If this is part of a science project, don’t spend so much time on the experiment that you skim through the reasons behind the color changes. It should just be an introduction, not the bulk of the project.

References

About the Author

Judith Willson has been writing since 2009, specializing in environmental and scientific topics. She has written content for school websites and worked for a Glasgow newspaper. Willson has a Master of Arts in English from the University of Aberdeen, Scotland.

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