Categories: Guide to Space

What is Boyle’s Law

It is interesting to think that at this very moment all of us, every living terrestrial organism, are living in a state of pressure. We normally don’t feel it the human body is primarily made up of liquid, and liquids are basically non compressible. At times, however, we do notice changes of pressure, primarily in our ears. This is often described as a “pop” and it occurs when our elevation changes, like when we fly or driving in the mountains. This is because our ears have an air space in them, and air, like all other gases, is compressible.

Robert Boyle was one of the first people to study this phenomena in 1662. He formalized his findings into what is now called Boyle’s law, which states that “If the temperature remains constant, the volume of a given mass of gas is inversely proportional to the absolute pressure” Essentially, what Boyle was saying is that an ideal gas will compress proportionately to the amount of pressure exerted on it. For example, if you have a 1 cubic meter balloon and double the pressure on it, it will be compressed to ½ a cubic meter. Increase the pressure by 4, and the volume will drop to 1/4 of its original size, and so on.

The law can also be stated in a slightly different manner, that the product of absolute pressure (p) and volume (V) is always constant (k); p x V = k, for short. While Boyle derived the law solely on experimental grounds, the law can also be derived theoretically based on the presumed existence of atoms and molecules and assumptions about motion and that all matter is made up of a large number of small particles (atoms or molecules) all of which are in constant, motion. These rapidly moving particles constantly collide with each other and with the walls of their container (also known as the kinetic theory).

Another example of Boyle’s law in action is in a syringe. In a syringe, the volume of a fixed amount of gas is increased by drawing the handle back, thereby lessening the pressure. The blood in a vein has higher pressure than the gas in the syringe, so it flows into the syringe, equalizing the pressure differential. Boyle’s law is one of three gas laws which describe the behavior of gases under varying temperatures, pressures and volumes. The other two laws are Gay-Lussac’s law and Graham’s law. Together, they form the ideal gas law.

For an animated demonstration of Boyle’s Law, click here.

We have written many articles about Boyle’s Law for Universe Today. Here’s an article about air density, and here’s an article about the Boltzmann Constant.

If you’d like more info on Boyle’s Law, check out NASA’s Boyle’s Law Page, and here’s a link to the Boyle’s Law Lesson.

We’ve also recorded an episode of Astronomy Cast. Listen here, Question Show: The Source of Atmospheres, The Vanishing Moon and A Glow After Sunset.

Sources:
http://en.wikipedia.org/wiki/Boyle%27s_law
http://en.wikipedia.org/wiki/Ideal_gas
http://www.chm.davidson.edu/vce/gaslaws/boyleslaw.html
http://home.flash.net/~table/gasses/boyle1.htm
http://www.wisegeek.com/what-is-boyles-law.htm
http://www.grc.nasa.gov/WWW/K-12/airplane/boyle.html

Matt Williams

Matt Williams is a space journalist and science communicator for Universe Today and Interesting Engineering. He's also a science fiction author, podcaster (Stories from Space), and Taekwon-Do instructor who lives on Vancouver Island with his wife and family.

Recent Posts

A Space Walking Robot Could Build a Giant Telescope in Space

The Hubble Space Telescope was carried to space inside the space shuttle Discovery and then…

23 hours ago

New Report Details What Happened to the Arecibo Observatory

In 1963, the Arecibo Observatory became operational on the island of Puerto Rico. Measuring 305…

2 days ago

We Understand Rotating Black Holes Even Less Than We Thought

The theory of black holes has several mathematical oddities. Recent research shows our understanding of…

2 days ago

Habitable Worlds are Found in Safe Places

When we think of exoplanets that may be able to support life, we hone in…

2 days ago

New Glenn Booster Moves to Launch Complex 36

Nine years ago, Blue Origin revealed the plans for their New Glenn rocket, a heavy-lift…

2 days ago

How Many Additional Exoplanets are in Known Systems?

NASA's TESS mission has turned up thousands of exoplanet candidates in almost as many different…

2 days ago