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Iodine and Starches Visual Science Experiment for Kids

Using iodine to identify starch is a fantastic visual science experiment for kids.

Using iodine to identify starch is a fantastic visual science experiment for kids. #stemed #sciencexperiment #sciencefair #sciencerocks #scienceforkids #homeschool #edchat #keeplearning #learneveryday

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The kids really enjoyed this simple experiment of using iodine to identify starch. I got to thinking about iodine after writing last week’s water post, because I remembered using iodine tablets to purify water when I went hiking on the Inca trail as a thirteen-year-old. It’s hard to visually explain that experiment, but the starch one is quite striking!

Getting ready to test for starch using iodine

Iodine and Starch Simple Experiment

Iodine is normally brown – not very attractive! Add it to starch, however, and you get a beautiful royal purple color! This makes for a truly striking visual science experiment that kids love.

I pulled out some iodine wipes (warning: iodine STAINS – be careful!), and we set up our experiment. Iodine in liquid form or tablet form can also be used; simply dissolve the tablets with a little bit of water for this experiment. I put flour, salt, and oatmeal on the plate, and then added baking powder on a whim, just to see what would happen.

How Do Everyday Pantry Items React to Iodine?

iodine remaining brown after coming in contact with salt

Salt doesn’t have any starch, so the iodine stays brown.

iodine turning purple after coming in contact with flour

Flour has a lot of starch! The iodine turned dark purple! We added a few drops of water with a syringe to help our drop of iodine to mix with the flour.

iodine turning purple after coming in contact with oatmeal

Oatmeal also has a lot of starch! It turned purple as well, although cooked oatmeal might have allowed the iodine to spread more thoroughly. Or a little more water =)

iodine reacting with baking powder

The baking soda bubbled up and turned purple at the edges. The purple is probably because most baking soda has some starch mixed in, but I’m still not sure why it bubbled. Does anyone know?

Update: It bubbles because baking powder contains baking sodamy IRL friend thanks to my IRL friend Kathy for reminding me of this! Baking soda reacts to acids, so the iodine must be slightly acidic. Here is Kathy’s explanation, if you would like the chemical details (thanks, Kathy!):

I think you created a chemical reaction with the Iodine (I2) baking soda NaHCO3 and water H20 to form a new chemical compound and also CO2 (gas) is a biproduct… which is what the bubbles would be… this is also what makes muffins, cookies, etc rise when baked is the release of the carbon dioxide gas…

Carla added in the comments:

Iodine wipes usually have povidone-iodine, which is a mixture of povidone, hydrogen iodide (which is very soluble in water and would form hydroiodic acid), and elemental iodine (which can act as an acid or base, depending on what you mix it with). Stirring baking soda (a base) into that should give you some excellent fizzing!

examining the results of their experiment

The kids thought this was fascinating – and very strange! Johnny asked us to put it in the fridge for a while to see if that changed anything. It didn’t, but I was thrilled to see him taking our experiment one step further!

A hands-on science and math resource for parents and educators

Have you tried this iodine and starch experiment with your kids? What did they think?

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MaryAnne at Mama Smiles
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MaryAnne is a craft loving educator, musician, photographer, and writer who lives in Silicon Valley with her husband Mike and their four children.

46 thoughts on “Iodine and Starches Visual Science Experiment for Kids”

  1. Heather Sullivan

    SO COOL!! This would be such a great experiment to do, thanks for sharing!!!

  2. This is really interesting – something to do with our own kids this summer. They love experimenting with things around the house. And just scrolling down to your comment section had me seeing lots of other things we can do together this summer.

  3. I love doing experiments with the kids using things/ingredients we have around the house – so much fun!

  4. This is really cool. I think my daughter will love it. Can’t wait to try it with her.

  5. I love this SO much! Very awesome experiment! I want to use this to make a detective chemistry lab! Also…the iodine/baking soda reaction is fantastic…Iodine wipes usually have povidone-iodine, which is a mixture of povidone, hydrogen iodide (which is very soluble in water and would form hydroiodic acid), and elemental iodine (which can act as an acid or base, depending on what you mix it with). Stirring baking soda (a base) into that should give you some excellent fizzing!

  6. I loved doing this when I taught Science – it was my first ever lesson and I still remember it after 10+ years.

    Thank you also for featuring our snow dough – I’ve linked up again this week with our first exploration of weighing with some snowmen crispie cakes.

    1. I think this is one of the funnest science experiments – so visual and so immediate!

      Thanks for linking up again!

  7. It looks like they were having a lot of fun learning! I just read in The Hunger Games where she used iodine drops to purify water. I’m sure I learned that at some point but I think I had forgotten ;)

    1. Apparently if you add vitamin C it gets rid of the icky iodine taste – and protects your from scurvy!

  8. What a fun experiment – my kiddos are very little, but I’m hoping to try a baking soda and vinegar investigation soon!

  9. Kim @ The Educators' Spin On It

    This is a great idea, I can’t wait to add this as a lesson in my Little Hands that Cook lessons so they can see why we add all these special ingredients.

  10. What a fun experiment! I remember getting a science kit as a kid and having lots of fun with iodine.

    Did you enjoy the Inca Trail as a 13 yo? It’s a dream of my husband and I to hike it but think we may need to do it without kids someday. We have been to Peru, but would love to hike the trail.

    1. It was an amazing experience. We hiked a four-day segment in Bolivia, starting at 14,000 feet the first day, hiking up to 16,000 feet, and then down to 8,000 over the next three days. Parts of the trail were missing, but our guide knew their way. The first day was pretty grueling, but after that it was (literally) all downhill. Definitely something I’ll remember forever!

  11. I love experiments like this! Thanks for sharing at We Teach. My kids and I did an experiment with purple cabbage not too long ago. We soaked a coffee filter with boiled purple cabbage water, dried the filter, and used our filter to test ph levels. I’m sure you’d find the directions for experiments like this online. We’re going to try your experiment with iodine and some of the others you’ve shared. Thanks!

    1. I keep meaning to make ph paper using cabbage – thanks for the reminder! And thank you for visiting from We Teach!

  12. Very fun! There used to be a unit called mystery powders something like this. Doesn’t any liquid and baking soda cause bubbles? Learning like this is so wonderful for your children. Love the photos. Carokyn

  13. You’re such an amazing, creative mom! I love all the activities you come up with to teach your kids throughout every day!

  14. Really cool! Very curious and had to look into it a little. Looks like baking soda reacts with acids. Iodine must be somewhat acidic…

  15. Funny, I accidentally did one part of your experiment when I was preparing our traditional gargle solution for Lars (he has a sore throat). Usually it’s soda, salt and iodine, but accidentally I put a baking powder instead. I didn’t see the bubbling, but my gargle turned purple. I was thinking of doing this experiment with Anna, since it’s very cool indeed.

    1. I think Anna would really enjoy this experiment! Another commenter as well as one of my IRL friend reminded me that baking powder has baking soda in it (don’t know how I forgot that!) and that is probably why it is bubbling – the iodine must be slightly acidic? The bubbling was very slight, so you might not see it in a solution.

  16. Elisa | blissfulE

    How interesting! I had no idea iodine reacts with starch. Love following along with you guys as you learn new things. :)

  17. We tried the iodine and starch thing when we did the murder mystery and it is so cool. I bet most of the foods I love have starch.

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