Sharon Endebak

Magic Wound

Science Concept:

Demonstrates that ions switch partners and cause a chemical reaction.

Materials:

iron chloride

ammonium thiocyanate solution or potassium thiocyanate

butter knife

Directions:

1. Place some iron chloride on hand and let it dry so the students can't see the iron on your hand.

2. Dip the butter knife into the ammonium thiocyanate solution (tell the students that you are sterilizing the blade).

3. Take the knife and pretend to cut your hand, actually slide the flat part of the knife on the hand to make a larger mark.

Introduction:

I don't know about you, but I didn't get a chance to eat lunch yet today. I am really hungry, so I brought a banana for a snack today. Do you want a piece? I will cut you each a piece. This knife is sharp, OW, I cut my hand!

As an alternative this is a good second demo to go with the lemon shell game.

Explanation:

On my hand I had iron chloride and the knife was dipped in potassium thiocyanate solution. When these two solutions came into contact, they exchanged ions or partners. This is sometimes called a switch partners reaction. The iron ions now bind with the thiocyanate ions instead of with the chloride ions. This reaction produced the blood-red color which was iron thiocyanate complex.

Iron chloride + ammonium thiocyanate Þ iron thiocyanate + ammonium chloride

FeCl₃ + NH₄SCN Þ FeSCN²⁺ + NH₄Cl + 2 Cl^1-

Safety:

No safety precautions need to be taken except to wash your hands thorougly afterward.

Disposal:

Solutions can be washed off with soap in the sink.

Reference: Unkown