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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! I pulled out some iodine wipes (warning: iodine STAINS – be careful!), and we set up our experiment. I put flour, salt, and oatmeal on the plate, and then added baking powder on a whim, just to see what would happen.
Salt doesn’t have any starch, so the iodine stays brown.
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.
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 =)
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 soda – thanks to Carolyn Wilhelm and my IRL friend Kathy for reminding me of this! As Ann noted in her comment, 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…
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!
What have you been exploring and learning lately? I got some fantastic ideas from last week’s link-ups: cloud dough from Rainy Day Mum, the brilliant suggestion of using easy-to-cut coffee filters to make snowflakes from hands on as we grow, and some great fine motor skill activities from The Mommies Made Me Do It. I really want to make this light table from Teach Preschool, and No Time for Flashcard’s playdough toy prints post has me motivated to make a new batch of playdough! I can’t wait to see what activities are shared this week!
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How interesting! I had no idea iodine reacts with starch. Love following along with you guys as you learn new things. :)
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Great experiment! I love Lily’s expression in the first and last pictures.
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maryanne Reply:
January 9th, 2012 at 10:07 am
She was fascinated – and perplexed =)
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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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Your such a good mom!
You kids get experiences in all aspects…experiments…sewing…art..outdoor adventures!
Amazing!
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Great experiment! They look very interested!
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I did not know about this iodine and starch experiment! Thanks for sharing:)
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I bet that was so cool for the kids to see the changes right before their eyes!
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maryanne Reply:
January 10th, 2012 at 7:23 am
They loved it!
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[...] shared with learning laboratory and made by little hands monday and monday madness and the sunday showcase and the learning [...]
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.
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maryanne Reply:
January 10th, 2012 at 7:24 am
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.
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You’re such an amazing, creative mom! I love all the activities you come up with to teach your kids throughout every day!
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Just found you site and this stuff is right up my kids alley. My 11 year old is a science nut, she loves experiments.
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Really cool! Very curious and had to look into it a little. Looks like baking soda reacts with acids. Iodine must be somewhat acidic…
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maryanne Reply:
January 10th, 2012 at 7:24 am
Thanks, Ann!
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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
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maryanne Reply:
January 10th, 2012 at 7:24 am
Somehow I forgot baking powder has baking soda – thanks for reminding me!
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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!
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maryanne Reply:
January 10th, 2012 at 10:36 am
I keep meaning to make ph paper using cabbage – thanks for the reminder! And thank you for visiting from We Teach!
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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.
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maryanne Reply:
January 10th, 2012 at 3:08 pm
What a great addition to the series!
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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.
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maryanne Reply:
January 10th, 2012 at 4:41 pm
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!
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This really looks like fun! JDaniel would love to see the chemical reaction.
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What a fun experiment – my kiddos are very little, but I’m hoping to try a baking soda and vinegar investigation soon!
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maryanne Reply:
January 11th, 2012 at 9:53 pm
Baking soda and vinegar was our first – I love that one, because it’s so accessible to even the youngest children. This is my kids’ favorite version: http://mamasmiles.com/sensory-play-with-baking-soda-and-vinegar/
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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 ;)
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maryanne Reply:
January 11th, 2012 at 9:56 pm
Apparently if you add vitamin C it gets rid of the icky iodine taste – and protects your from scurvy!
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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.
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maryanne Reply:
January 12th, 2012 at 9:14 am
I think this is one of the funnest science experiments – so visual and so immediate!
Thanks for linking up again!
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Such an interesting experiment! And great pictures! They show everything so well. Thanks for sharing on weteach.
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What a great experiment, so simple, but so interesting! Thanks for linking to Fun Sparks. x
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ooooh, I know a little scientist who will LOVE this, thank you!
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MaryAnne Reply:
January 3rd, 2013 at 3:06 pm
Wonderful!
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