Equipment:

• 1L flask with a bottom well and a cork
• Bunsen burner and ring stand
• Thermometer (large display and a thermocouple)
• Bucket of ice
• Insulating gloves

Demo:

1. A round flask half-filled with water is heated with a Bunsen burner until water begins to boil. A large display connected to a thermocouple shows the water’s temperature.
2. The flask is removed from the burner and sealed with a cork (thermocouple remains inside). After a minute, the temperature drops by several degrees.
3. The flask is flipped and ice is placed in its bottom well (see picture to the right). The audience will see that the water starts boiling again at lower temperature.

Explanation:

This demonstration shows how water boils at a lower temperature when pressure is reduced.  The water begins to cool as we take it off the bunsen burner and flip the bottle. When we add the ice it then cools the air in the flask causing it to shrink. This creates a lower pressure creating a lower boiling point.