Praxis: Taste the scientific rainbow

By Medicine Hat News on November 4, 2017.

What a busy week it has been! I am sure many of your little ghosts and goblins were out tricking but hopefully more treating! If you are like me, you are wondering what to do with some of that candy that is still sitting in a bowl on your cupboard. Well, do not despair, science to the rescue. Let’s get started!

*Remember to ask an adult before doing this experiment.

Materials

– one small package Skittles candy

– straw

– cone type coffee filters

– scissors

– clear glass

– clear cup

– water

– large binder type paper clips

– plate

– ruler

– pencil

– pipette/medicine dropper

– kettle salt

– measuring spoons

– toothpicks

– shallow pan or dish

Procedure

1. Using a ruler, measure a 10cm x 8cm strip of the coffee filter. Cut out and discard the extra, you will only need this one strip.

2. Lay the strip on a flat surface where you will be working.

3. Using the pipette, place four drops of water evenly spaced out on a plate.

4. Place a Skittles candy in each of the four drops. Use a different coloured candy in each drop of water.

5. Allow to sit for several minutes until the water turns the same colour as the candy once was.

6. Using the toothpick, pick one colour and dip in the colour mixture on the plate and then onto the coffee filter. Continue to do this until you have a nice colourful spot about the size of a pencil eraser on the coffee filter. You do not want too large of a dot as it will just blend into the next colour.

7. Repeat for the next three colours. Be sure to leave an even space between each colour.

8. Please have an adult help you with this step. You will now make a salt solution. Measure 5 mL (one teaspoon) of salt into a cup and add 250 mL (one cup) of boiling water. Stir well until the salt is completely dissolved.

9. Pour the salt mixture into a shallow pan or dish.

10. Allow the mixture to cool slightly while you move on with the experiment.

11. Fold the coffee filter over to the opposite side you have placed the coloured dots. Lay the straw across the top of the filter paper — opposite the coloured dots.

12. You will hold the straw in place by clipping on the binder clips.

13. Take the coffee filter and hold it above the shallow pan of salt water. Just allow the bottom edge to touch the salt water.

14. What happens?

What is going on?

In this experiment, you did candy chromatography. This is a chemistry experiment. Chromatography is a way of separating many different kinds of chemical mixtures. It can also be used to separate mixtures of coloured components as you did in this experiment. As the solvent (salt water) soaks up onto the paper (coffee filter), it carries mixtures with it up the filter paper. This is important as in chemistry we know that different components of the mixture will travel at different rates allowing the mixture to separate out into its components. You should have observed this on your filter paper. The different colours should have separated out at different lengths. It does get a bit complicated but chemists often use this rate (an Rf value) to identify different mixtures and compounds if they do not know what they are.

Patty Rooks is senior scientific consultant at 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.

38
-37