Dive Science: How Charles’ Law Applies to SCUBA Diving

charles' lawWhether in tropical reefs or mountain lakes, SCUBA diving allows you to explore a unique world only experienced while underwater. Divers rely on equipment to adapt and become part of the underwater world, and having a basic knowledge of science helps ensure safety while diving. A common example of this is with Charles’ Law.

Charles’ Law states that at a constant volume, the pressure of gas varies directly with absolute temperature. While this law was published by a French philosopher named Joseph Louis Gay-Lussac, Lussac attributed the law to an unpublished work by Jacques Charles. Charles wrote about the law after observing the effects of temperature on balloons.

Understanding Charles’ balloon example can help a diver better understand how the law impacts diving. When a balloon is filled with gas and exposed to heat, the molecules of the gas accelerate, causing the balloon to expand. When the balloon is exposed to colder temperatures, the molecules of the gas slow down, causing the balloon to deflate. This concept is the same in regard to air in a SCUBA tank.

charles' lawThe gas in a SCUBA tank reacts the same way to temperature as air in a balloon. However, the walls of a tank are rigid with little to no flex, while the elasticity of a balloon allows it to expand. Since water temperatures while diving are typically colder than the outside air, and the friction caused when filling a tank heats up the air inside, a diver may have less gas volume in their tank than they expect. To combat this, many dive shop owners will overfill air tanks to make up the difference. This law is also important for storing filled SCUBA tanks, as tanks left in hot cars or boats may weaken and in rare cases explode under the increased temperatures. To prevent this, modern tanks have a safety plug that will split and allow pressure to escape before exploding.

Stay tuned for more explanation of how certain laws of science apply to SCUBA diving!

Images via web2.uwindsor.ca, ssl.umd.edu

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