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What is Boyle’s Law?

Chemistry | 7-14 yrs | Interactive

Definition of Boyle’s Law

Boyle’s Law is an experimental gas law that describes how the pressure of a gas tends to increase as the volume of the container decreases. It is named after the chemist and physicist Robert Boyle.

What does Boyle’s Law state?

According to this law : If a fixed amount of ideal gas is kept at a fixed temperature, the pressure (P) and volume (V) are inversely proportional, that is, when one doubles, the other is reduced by half.

What is an ideal gas?

An ideal gas maybe defined as a theoretical gas composed of molecules on which no forces act except upon collision with one another and with the walls of the container in which the gas is enclosed.
It is a gas which perfectly follows Boyle’s Law.

Why is Boyle’s Law important?

Boyle’s Law is important for us to understand how gases behave under pressure.
The practical uses of Boyle’s Law is seen all around us everyday.

Practical applications of Boyle’s Law

  1. Medical syringes use this principle. The plunger creates a space when it is pulled back and reduces the pressure in the tube. The fluid draws up inside the tube, because of this low pressure inside, balancing the pressure inside to pressure outside.
  2. When you climb high altitudes or are in an aeroplane, your ears ‘pop’ or you feel uncomfortable because of a change of pressure in your head. This is because the pressure inside the body is not in balance with the pressure outside which is lower at high altitudes. This is against Boyle’s Law. So your body has to undergo a period of acclimatisation.
  3. Deodrants and other spray cans work on Boyle’s Law. The compressed air, which is in the can, is a liquid because its boiling temperature is lower than room temperature. This gets released as the nozzle is pressed. Once the seal is released, the liquid inside the container expands and becomes a gas. So you get a whiff of your favourite smell, or a coat of paint.
  4. Popular aerated drinks and sodas also use Boyle’s Law. Carbon di oxide gas is mixed with syrups and water to make soft drinks. Mixing Carbon di oxide increases the pressure in the liquid making it fizzy, which is what aerated drinks are about!
  5. Deep sea diving also uses an understanding of Boyle’s Law to acclimatise deep sea divers.
    When deep sea divers go under water, after a certain point, while the pressure in their body is still at sea level, the pressure at deep sea level is high. As the divers descend, pressure inside the body increases along with the fact that they are breathing in compressed air from air tanks. When the divers start their ascent, they have to decompress at different levels to release the pressure and the mixed gases inside them. The different pressures inside and outside, plus the the fact that compressed air starts expanding as the ascent begins can cause air bubbles in between tissues and cells, which can cause severe damage, even death.