Tuesday, September 8, 2009

Acid Test

This experiment was invented by Loralee Leavitt.  Please do not copy, sell, post, publish, or distribute all or any part of this material without my permission. Instead, feel free to link to this website, and to contact me with questions.

Sour taste is the body's way of identifying acid, so if your candy tastes sour, it contains acid.
Pixy Stix acid test:
adding baking soda causes bubbles

To test for acid yourself, try this:

What you need:

  • Fruit-flavored or sour candy, such as LemonHeads, Nerds, WARHEADS, or sour gummy candy
  • Baking soda
What to do:
  1. Dissolve the candy in a small amount of warm water (about a half-cup or less). For hard candy like Smarties, you may want to crush it first to make it dissolve faster.
  2. Sprinkle a spoonful of baking soda into water.
  3. Watch for bubbles.  If it bubbles, the candy is acidic.
What's happening: 
When you dissolve acidic candy in water and add baking soda, the reaction produces carbon dioxide gas.  This is what makes the bubbles.

For more fun, try testing candy like Skittles, StarBursts, or Sweet Tarts.  Do these candies contain as much acid as really sour candies?

*If the candy is taking too long to dissolve, try crushing it first.  You can also get quick results using Pixy Stix or candy covered by sour powder.

Video results: watch acid tests on Youtube
Explanation based on author's interview with Walter Bowyer, chemistry professor at Hobart and William Smith Colleges


  1. Were there a lot of bubbles? We saw a few and not for very long. Some there were no bubbles at all. Curious to know what your results were.

  2. In general, the more sour your candy, the more bubbles you will get (because it contains more acid). Skittles and Starbursts produce a few bubbles, Nerds produce more, and sour coated candy such as Warheads and Sour Patch Kids produce the most.

    Unless the sour coating is on the outside, make sure the candy dissolves before you add the baking soda. If the whole candy is sour, the more it dissolves the more bubbles you will see when you test it.

    You might invite your child to sort the candy by predicting which will produce the most bubbles, based on how sour they are. Then dissolve each candy in a separate cup and add baking soda to test your predictions.

  3. I adore your site! I just posted a link to yours on my blog: creatingcuriouskids.wordpress.com Here's to candy science!

  4. Curious kids are what got us started on candy experiments in the first place, so hooray for scientific curiosity. Thanks for the note!

    1. Loralee my daughter has a science project and we saw your post may we use this

    2. That would be fun--let me know how it goes! Here's what we did last year for an Acid Test science fair experiment.

    3. Acid test science fair experiment:

  5. Rachel of Momma Owl's Lab just tried the acid test at home, expanding it by 1) testing Smarties in baking soda water vs. plain water, 2) testing crushed vs. uncrushed to teach about surface area, 3) suggesting hot vs. cold or 4) suggesting 1 cup of water vs. a few TBSP. All great ways to learn about reactions. You can see her full entry at http://mommaowlslab.blogspot.com/2011/11/science-thursday-smarties-science.html

    I've been trying to keep my online experiments simple so they're easy to follow, but my book Candy Experiments, coming out next year, will have lots more of these kinds of experiments. Don't worry, they'll still be fun!

  6. If you're asking about making a cabbage indicator to test for acidity, the cabbage needs to be purple so that you can see the color change. It's pretty easy to do--chop up some purple cabbage and boil it, then strain it and keep the water as indicator (or, if you have your kids do it, have them rip up the cabbage and let it soak in water for an hour). When you add acid to the indicator, it should turn pink; if you add a base (like baking soda) it should turn blue.

  7. Hello my daughter came across your experiment and she wants to try it for her science project my we use it please. She said if you let her she's putting you down for the background research.

  8. That would be fine. Let me know how it goes!

  9. Loralee. My son loves this experiment and we are doing this for science fair. May we please reference the information on this page. We would post it on his board, reference it on this video we are making (they get to incorporate ipads into the presentation) and put it in the report. We would ensure that your work is correctly cited.

    We are testing war head, smarties, lemon heads, now and laters, sour crawlers, and jelly beans. I had him taste the candies and rate how sour they were and then we read the label to find out what kind(s) of acid was used to make the candies.

    1. Go ahead. Thank you so much for asking! I would love to hear what your results are, and how your testing compares to his tasting.

  10. Hello!

    This project sounds like a ton of fun! My son would like permission to use it for the Science Fair this year if that's ok. Thanks

  11. Go ahead, and thanks for checking.

  12. Would love to use the this experiment for a STEM enrichment program I teacher at a local preschool. I always send written material home with the kids and will happily add your site to that material. Is this OK?

  13. Go ahead and use this for your preschool. On your written material, please include the book title as well as the website. Thank you so much for asking, and let me know how it goes!

  14. Hi! My experiment didn't have much bubbles but I didnt see it. My partner did it. I asked u if I could use it already. Guess who I am??????

  15. Hi!!!!! My experiment isn't going that well. What can I do to improve it? I didn't do it, a partner did so I only know because she told me. I had already asked you for the permission for using the experiment. Let's see if you can guess who I am and what my e-mail was!!!!! :)

  16. If you're trying to compare the acidity of different candies, try this:
    --dissolve the candy in warm or hot water. This will help it dissolve better. Dissolve as much as you can, at least of the sour part.
    --make sure you are using equal amounts of each candy. You might want to weigh each sample.
    --add the baking soda after the candy is dissolved. You can also mix some baking soda and water together until the baking soda dissolves completely, then add an equal spoonful of that to each bowl. This ensures that you've added exactly the same amount of baking soda to each sample.
    --Most candies don't produce very many bubbles. So watch closely. Good luck!


Comments will be displayed after they are approved.