Rising Water

Purpose:

To demonstrate interactions with atmospheric pressure and the volume difference between a liquid and a gas.

Materials:

• Hot plate
• Large graduated cylinder
• Large beaker

Reagents:

• Food coloring (any color)

Hazards and PPE:

• Heated glass and boiling water are dangerous to touch.
• Wear approved safety goggles and gloves.

Protocol:

Demonstration

1. Fill large beaker about halfway with water. Add a few drops of food coloring.
2. Place graduated cylinder upside down in the water. Ensure water rises to exterior level within cylinder.
3. Place beaker on hot plate. Boil water and continue heating for several minutes. Bubbles should be coming out of the cylinder.
4. Remove beaker from the heat. Water should rise into cylinder.

Disposal:

• Water with food coloring can be poured down the drain.

Reactions:

• Water vapor from the boiling water fills the cylinder, pushing the air out (hence the bubbles) and lowering the pressure above the water in the cylinder.
• Atmospheric pressure pushes the water into the cylinder once the vapor cools and condenses.

Citations:

1. This demo adapted from the demo library of the Chemistry department at the University of Illinois at Urbana-Champaign.