Vapor Pressure and Boiling Point: Water Boils at Room Temperature (Kari Kelly)

Author

Kari Kelly

Principle(s) Illustrated

1. Definition of Boiling

2. Air Pressure

3. Vapor Pressure

Standards

PS1-A

The structure and interactions of matter at the bulk scale are determined by electrical forces within and between atoms.

PS2-B

Attraction and repulsion between electric charges at the atomic scale explain the structure, properties, and transformations of matter, as well as the contact forces between material objects.

Questioning Script

Prior knowledge & experience:

Students know that water boils when enough heat is added. Students know that boiling water is hot.

Root question:

How can we make water boil?

Target response:

The boiling point is the temperature at which the vapor pressure of a liquid equals the external pressure surrounding the liquid. Therefore, the boiling point of a liquid depends on atmospheric pressure. The boiling point becomes lower as the external pressure is reduced.

Common Misconceptions:

Water must be hot to boil. Boiling is directly related to the amount of heat added.

Photographs and Movies

References

Vapor Pressure and Boiling Point Graph