Water Magic Tricks

Bending a Stream of Water

Code Name

Electrostatic attraction of water
Demo #: Gen.5
Reference: Chemical Demonstrations: A Handbook for Teachers of Chemistry, Vol 2: p. 91

Equipment

• 2 x 50 mL burettes with double burette clamp and stand
• 2 x 400 mL beakers
• Rubber or plastic rod
• Piece of wool or fur

Chemicals

• Distilled water
• Hexane

Procedure

1. Fill one burette with hexane and the other with distilled water.
2. Adjust the stopcock on the water burette to create a fine unbroken stream into a 400 mL beaker.
3. Charge the rubber or plastic rod with the wool or fur, and demonstrate that water is attracted to the rod (ensure the water does not touch the rod).
4. Repeat the demonstration with the hexane burette to show that hexane is not attracted to the rod.

Variation

• Use a vinyl plastic strip charged with wool to show that water is attracted to a negative charge.
• Use a piece of acetate plastic charged with a paper towel to show that water is attracted to a positive charge.
• This demonstrates that water has both a positive and a negative end.

2. Disappearing Water

Code Name

Sodium polyacrylate gel
Demo #: Gen.17
Reference: Commonly known

Equipment

Part A:

• Small glass (with even lip)
• Piece of cardboard

Part B:

• Styrofoam cup
• Piece of cardboard with “Do not remove this cardboard” written on both sides
• Water pitcher

Chemicals

• Jug of water
• Sodium polyacrylate powder

Procedure

Part A:

1. Fill the glass 3/4 full with water.
2. Place the cardboard over the mouth of the glass and invert it.
3. Release the cardboard; the water remains in the glass.

Part B:

1. Pre-fill a styrofoam cup with sodium polyacrylate powder (unseen).
2. Have a student hold the cup in the air with both hands.
3. Pour water from the pitcher into the cup and cover the mouth with cardboard.
4. While the student is still holding the cup, turn it upside down over their head and lower it onto their head.
5. Pull the cardboard out and have the student read the card. Finally, lift the cup off their head to show that no water comes out.

Explanation

Part A: As the water tries to exit the glass, the pressure inside decreases, allowing atmospheric pressure to hold the cardboard against the rim of the glass.

Part B: The sodium polyacrylate quickly forms a gel when water is added, preventing it from escaping.