Mile High Experimenting

March 31, 2015

This spring’s ACS meeting was miles above the rest— or at least one mile above most others since it was hosted in Denver, CO. While we were in the Mile High City, we decided to do a mile high experiment— but in our case, we were thinking about altitude, not the other kind of high that might be popular since becoming legalized in Colorado.

One difficult concept for students to grasp is that the boiling point is the temperature when the vapor pressure of a liquid is equal to the atmospheric pressure. The boiling point of water does not have to equal 1000C because other factors come into play.

In our case, we wanted to see how the altitude in the mile high city impacted the boiling point of water. What better way to illustrate how the boiling point changes based on atmospheric pressure? First we wanted to get a measure of the atmospheric pressure at altitude so, we took our Chemistry Sensor, AirLink 2 and iPad® up the steps of the Colorado State Capital building.

Denver Steps

The screen is difficult to see, but the reading tells us that the atmospheric pressure on this beautiful sunny day was ~83 kPa, well below the standard 101.3 kPa.

If the boiling temperature is dependent on the atmospheric pressure, what is the boiling point at ~83 kPa? 

There’s only one way to find out. With a hotel room substituting for a lab, we used our Chemistry Sensor with a Fast Response Temperature Probe to monitor some boiling water. The first major discovery?  Contrary to popular belief, a watched pot will actually boil.

Boiling Point

You can see from the picture that the water was rapidly boiling and the temperature had plateaued.  

Boiling point Screen shot

The temperature where the water boiled was ~950C -  significantly below the normal boiling point. The misconception is that water always boils at 1000C. But as we discovered in the Mile High City, the temperature required to reach boiling was actually a little low.

It was great to meet all of the chemists at ACS during High School Day, at the Young Chemistry Educators Society Social, and all the visitors to the PASCO booth— including the ACS Mole!

Looking forward to seeing everyone at future conferences, where we’ll have more opportunities to #thinkscience!


Related Product:

  • PASPORT Chemistry Sensor (PS-2170)