Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Altitude, Temperature and Pressure
Name: Fred
Status: other
Age: 30s
Location: N/A
Country: N/A
Date: 1999-2001

water boils at a lower temp. at higher altitudes does altitude affect the temp. at which water will freeze?

The reason that altitude affects the boiling point is that the air pressure is less the higher the altitude. Since the volume change upon going from the liquid state to the gaseous state (in other words, boiling) is so large, pressure makes a big difference. Expanding against a high pressure takes a lot more energy than expanding against a low pressure, so you have to put a lot more energy (as heat) into the system to boil at lower altitudes.

The volume change upon melting is much smaller than the volume change upon boiling. In fact, the volume decreases when ice melts. So, higher pressures favor the liquid state over the solid state. As a consequence, the melting point (which is the same thing as the freezing point) of water will actually DECREASE as the pressure increases, opposite the direction the boiling point moves. The size of the change, however, will be VERY small compared to the change in the boiling point.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois

Click here to return to the General Topics Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory