Why 7,000 Feet Can’t Deliver a Free Lunch

Mexico is a mountainous country, and many of its towns and cities away from the coasts are situated at altitudes of least 5,000 feet above sea-level, and often higher than 7,000 feet above sea-level.

If you are living or retiring in Mexico, or plan to visit here on a self-catering vacation, a consideration to take into account is that the altitude has an effect on food preparation, because water situated at higher altitudes boils at lower temperatures.

The science is quite simple.  The atmosphere surrounding the Earth creates pressure against all objects within it.  Barometric pressure at sea level equates to a little less than thirty inches of mercury, or 14.69 pounds per square inch.  At this pressure level, water boils at 100 degrees Centigrade (212 degrees Fahrenheit).

However, as the altitude increases, the density of the air becomes thinner (which is why it’s harder to breathe at higher altitudes) and the pressure continues to drop constantly until you reach space, where there is no air, no density and no pressure.

Water thus boils at a lower temperature because the pressure on the water molecules is lower at higher altitudes, requiring less energy for the molecule bonding threshold to be reached (the point at which molecules break away and coalesce into steam).  And so, because less heat (energy) is required to break up the molecules, the water boils at a lower temperature.

For example, at 5,000 feet above sea-level water will boil at 94.9C (202.9F); at 6,000 feet water boils at 93.8C (200.9F); and at 7,000 feet water boils 92.7C (198.9F).  This online calculator works out the figures.

Some tea-drinking connoisseurs argue that coffee is a better beverage option when one is situated in high altitude areas, because tea requires a high water temperature to provide its “proper” tea taste.

In terms of cooking food, you won’t experience an energy gain (e.g. use less gas) to cook your meal because although the water reaches boiling point sooner, you need to leave your food cooking for longer.  An example is preparing a hard-boiled egg.  If it takes five minutes to hard-boil an egg at sea-level it will take proportionally longer at higher altitudes; so any gain realized through lower boiling points is lost in the longer while it takes for the heat-energy transfer to take place.

This is another way of demonstrating that there really is no such thing as a “free lunch” – not even in high places.