Science Smarts:

By Patty Rooks on January 21, 2023.

It is time to get a little messy! Chemistry experiments are always fun to do as they often involve a colour change. Do not be afraid, this experiment is a bit longer, but trust me, well worth the effort. Not to mention, I absolutely love that we can find the materials right in our pantry – no unnecessary trips to the store to purchase anything extra. Let’s get started!

*Remember to ask an adult before doing this experiment. Caution: Iodine is used in this experiment, which is poisonous. When doing this experiment, adults should be present to ensure the iodine is used correctly.

Materials

– Potatoes

– Tincture of iodine *poisonous*

– Apple

– Cornstarch solution

– Distilled water

– Newsprint

– Eye droppers

– Knife or scalpel

– Rubber gloves

– Plate or dish

– Safety goggles

– Empty plastic container

– Measuring cup

– Measuring spoon

Note: to make a cornstarch solution:

Procedure I Making a Starch Solution

1. Mix two tablespoons of cornstarch with four tablespoons of cold water. It should make a paste.

2. Fill a kettle with distilled water and bring to a boil.

3. Measure one quarter of a cup of water.

4. Pour the boiling water into a bowl.

5. Slowly stir in the cornstarch mixture.

6. Stir well and quickly as it may form lumps.

7. Set aside and allow to cool.

Procedure II

1. Put on your rubber gloves and safety goggles.

2. Cover your work area with a couple of layers of newsprint. Iodine can be very messy and will stain anything that it touches.

3. Cut a piece of raw potato and set aside.

4. Cut a piece of apple and set aside.

5. Place one quarter of a cup of distilled water into a plastic container and set aside.

6. Place one drop of iodine in the distilled water. What do you see?

7. Repeat #5 for the apple, potato and cornstarch solution. What do you see?

Explanation

Iodine is often used as a test for starch.

When you placed the iodine in the distilled water, the control, it should have been a yellowish brown colour. This means there is no starch in the water.

When you placed the iodine in the cornstarch solution, it should have turned bluish black. This is because there was a chemical reaction between the starch and the iodine.

The apple and the potato should have also turned bluish black because they also have starch in them.

Try this experiment with other materials you can think of. Do they contain starch?

Teachers – if your school is interested in having a science fair club, make sure you call soon so I can pop by and give you some great pointers!

Patty Rooks, Senior Scientific Consultant PRAXIS, “Connecting Science To The Community”. Contact Praxis at praxis@praxismh.ca, http://www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook. Address: #12 826 11 Street S. E., Medicine Hat, Alberta, T1A 1T7 Phone: 403.527.5365, email: praxis@praxismh.ca.

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