Sandie Koontz

Powder Glove

Science Concept: Surface tension is caused when many water molecules link together to form a "skin." The surface of water is strong enough to keep the powder from mixing into the water.

Materials:

-600 ml beaker
-50 ml beaker

-Water

-Lycopodium Powder

Directions:

• Fill the 600 ml beaker 3/4 full of water.
• Sprinkle a thin layer of lycopodium powder on top of the water.
• Fill the 50 ml beaker full of water and put it into the large beaker so that is upside down.
• Put a coin on top of the upside down beaker.
• Push three fingers into the powder, and wiggle around a bit so everyone can see, and pull them straight out. There will be powder on your finger, but no water. To prove this snap your fingers and watch the dust fly.
• Repeat to pull out the coin.

Introduction:

Today I have a magic trick for you. I bet you I can put my hand in this jar and grab that penny, without getting my hand wet.

Explanation:

Lycopodium powder will not mix with the water because it is hydrophobic or water hating. Actually the water is polar, and the powder is nonpolar. These properties mean that the two substances will not dissolve or mix with each other. The molecules of the powder try to stay away from the molecules of the water. In addition, the powder is mostly less dense than the water and will float on the top.

When you stick your hand into the powder and water, the force of your hand makes the powder particles stick to your fingers and push the molecules of the water away, therefore the powder is like a water repellent.

This demo almost works with talcum powder.

Safety: Lycopdoium powder is a very fine dust. Take care not to inhale it.

Disposal: Pour in drain and rinse.

Reference: Unknown