? Science with Sarah: Iodine & starch tincture ?

? Watch the video of Sarah’s school science experiment here!

Hello parents, teachers and students! If you’re looking for fun way to explore chemistry with you middle-school aged kiddos, this experiment is for you!

Be sure to check out GMSA@9 on Wednesdays when Meteorologist Sarah Spivey does the demonstrations and explains the science behind it.

Science with Sarah: Invite KSAT to your school for live science experiments. (KSAT)

HERE’S WHAT YOU’LL NEED

Eye protection

Apron (Optional)

Gloves (Optional)

Aluminum foil

2 clear plastic cups

Cornstarch

A spoon

Pipettes (Amazon link)

Iodine (Amazon link)

Potatoes (sliced), Bread slices, bananas (sliced), lettuce, apples (sliced)

DO THE EXPERIMENT

STEP 1: Wear eye protection! You don’t want to get iodine splashed in your eyes. Also, iodine can stain, so wear an apron or gloves if you want to avoid stains

STEP 2: Lay out some aluminum foil as your workplace

STEP 3: Fill the two cups about 3/4 full of water

STEP 4: Using the spoon, add a scoop of cornstarch to one of the cups and stir.

STEP 5: Take a pipette’s worth of iodine and put it in the cup of water without the cornstarch. Notice that the iodine turns the water a pale yellow color.

STEP 6: Take a pipette of iodine and squeeze it into the cup with cornstarch. The water should turn a deep purple, blackish color as the iodine reacts to the starch. See picture below

STEP 7: Now, test the various food items for starch by placing a few drops of iodine on each food item. If the food contains starch, the drops of iodine should turn a very dark color.

HOW IT WORKS

This experiment explores the chemistry of electrically charged iodine molecules. In the first-aid mixture of iodine, like the one used for the experiment, the iodine breaks down electrically when introduced to starch.

We see the deep purple color as a result of the higher energy level emitted by the iodine-starch mixture. See the example of iodine on starchy bread below.