Boyel’s Law and Its Applications

In the last post we have studied the Boyel's law. In his experiment Robert Boyle showed that when a gas gets compressed, same number of molecules come closer and get fitted in a smaller volume. If we increase pressure twice, the volume of gas decreases to half.

Do you know we encounter Boyel’s law many times in our daily life? Science is everywhere around us and we use it all the time knowingly or unknowingly. 

Did you ever try to fill air in the tube of your cycle by mouth? Why couldn’t you succeed in that? And why it can be done so easily when you use a pump. Because by mouth you couldn’t create enough pressure to push air in the smaller volume of tube but when you use pump it exerts extra pressure and forces air to fill in a smaller volume.

We use this law in water guns and syringes. To understand how, you have to review the law to see how pressure and volume counter act each other. If pressure is increased, it decreases the volume and vice versa. When you pull the lever to fill water/liquid, it decreases the pressure inside which results in increase in volume, so higher number of molecules can be filled in it. And when you push the lever, you exert pressure which decreases the volume and molecules are forced out of the gun/syringe through its opening.

Now you can find more examples from your daily life. Deodorant spray, spray paints are also using boyel’s law. As you press the nozzle, it eases pressure and increases volume which causes molecules to come out forcefully.   

Our body uses this simple phenomenon 24 hours a day. Yes, your guess is correct, breathing. Every time we breathe, our lungs expand by contraction of diaphragm, which increases volume and decreases pressure inside the lung, this causes air to rush in at the time of inhalation. For exhalation, diaphragm relaxes, reducing the volume of lungs, which increases the pressure and causes air to get expelled from the lungs.

This knowledge can save your life when you go for deep sea diving, let’s see how. Our body is accustomed to live in atmospheric pressure, atmospheric pressure increases when you go deep in water which adds pressure of water too. If you descend slowly, your body can manage the change in pressure but when you descend quickly, sudden increase in pressure causes decrease the volume and nitrogen molecules start getting absorbed in blood. And when you ascent quickly, these nitrogen molecule try to escape and any built up nitrogen between the diver's joints will also want to expand. This causes the diver to bend over and experience severe pain.

Another scientist Charles experimented to see the effect of temperature on volume of gas at constant pressure. In our next post we will see how his experiment leads us to a trip on hot air balloon.

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