Question
Thu July 05, 2012 By:

why it takes longer to boil an egg at higher altitude? give proper explanation?

Expert Reply
Sat July 07, 2012

The atmosphere of air surrounding the earth creates a pressure against us and all objects on earth. This pressure at sea level is one atmosphere, (14.696 pounds per square inch (psi)), or if measured in mercury - 760mm (approx. 30 inches of mercury) in a column. It is the density of the atmosphere, or air, that causes the pressure.

As you increase altitude, the density of the air becomes thinner, and this thinner or less dense air then exerts LESS pressure. So, the higher the altitude the less dense the air and pressure decreases, until in space - no air, no density, no pressure.

Now, to boil water requires energy, this energy is in the form of heat and may have been produced by gas flame, electrical, solar, burning wood etc. As the water molecules are heated, the energy of the water molecules is increased, and they will vibrate or become more agitated, until finally the water molecules will break loose from the surrounding liquid water and rise up as steam. The water will also move quite violently due to the expanding dissolved gases that are contained in the water - hence the bubbles seen moving rapidly to the top of the boiling water.
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