The ABC's of gas: Avogadro, Boyle, Charles - Brian Bennett

Transcriber: Tom Carter
Reviewer: Bedirhan Cinar

In society, we have to follow laws that maintain order. Did you know all chemical matter follows certain laws as well? In fact, we can describe those laws by looking at relationships. Some easy laws to begin with are the ones that govern the gases.

Back in 1662, Robert Boyle realized that gases had an interesting response when he put them into containers and changed their volume. Take an empty bottle and put the cap on it, closing that container. Now squeeze your bottle, and what happens? The pressure inside the bottle increases when the size of the container decreases. You can only crush that container so much until the gases inside push back on your hand. This is called an inverse proportion, and it changes at the same rate for every gas.

Boyle's law allows chemists to predict the volume of any gas at any given pressure because the relationship is always the same. In 1780, Jacques Charles noticed a different relationship between gases and their temperature. If you've ever seen a hot-air balloon, you've seen this law in action. When the balloons are laid out, they're totally flat. Instead of blowing the balloon up like a party balloon, they use a giant flame to heat the air inside that envelope.

As the air is heated up, the balloon begins to inflate as the gas volume increases. The hotter the gas becomes, the larger the volume, and that's Charles' law. Notice this law is different from Boyle's. Charles' law is a direct relationship. As the temperature increases, the volume increases as well.

The third law is also easily demonstrated. When you're blowing up party balloons, the volume increases. As you are blowing, you're forcing more and more gas particles into the balloon from your lungs. This causes the balloon volume to increase. This is Avogadro's law in action. As the number of particles of gas added to a container are increased, the volume will increase as well.

If you add too many particles, well, you know what happens next. Laws are everywhere, even in the tiniest particles of gas. If you squeeze them, the pressure will increase as the particles are pushed together. Low volume means a high pressure because those particles push back. As the temperature increases, gases move away from one another, and the volume increases as well.

Finally, if you add gas to a closed container, that container's volume will expand. But be careful not to add too much because otherwise you could end up with a burst balloon.