Measurable Properties of Gases: Gas Laws – Boyle’s Law

Introduction

Several scientists created gas laws around the end of the 18th century. Each gas rule is identified by the names of the scientists who proposed it. As a result, we now identify the following five key gas laws. Boyle’s Law describes the link between a gas’s pressure and volume. The connection between the volume filled by a gas and its absolute temperature is given by Charles’ Law. 

The connection between the pressure exerted by a gas on the walls of its container and the absolute temperature associated with the gas is described by Gay-Lussac’s law. The link between the volume occupied by a gas and the amount of gaseous material is given by Avogadro’s Law. By combining the preceding four rules presented by four different scientists, the Combined Gas Law, often known as the ideal gas law, may be created. 

Although the combination of these rules explains the behaviour of an ideal gas, they are quite similar to the behaviour of actual gases. Under typical conditions, all gases act similarly. Variations in behaviour are seen when the physical conditions vary. Temperature, pressure, and gas volume are examples of physical parameters. Changes in these characteristics cause gas behaviour to alter. As a result, the gas laws characterize these variations in gas behavior.

The amount of the gas (mass)

(i) Suppose someone weighs the container in which the gas is contained. Then, if she weighs it again after the gas has been extracted, the mass of the gas can be computed. The difference between the two weights determines the mass of the gas.

(ii) The mass of the gas is proportional to the number of moles of gas, i.e. (n)

Moles of gas (n)=(Mass in grams)/(Molar mass)

                          =m/M

(iii) Mass is expressed in grams or kilograms, 1 Kg=103g.

Volume

(i) Determining the volume of a gas simply needs a measurement of the container in which it is contained because gases take up all of the available space,

(ii) The units of volume are liters (L), milliliters (mL) or cubic centimeters (cm3), or cubic meters (m3).

(iii) 1L = 1000 mL

1mL=10-3L

1L =1dm3 =103 cm3

1m =103dm3 =106 cm3 =106mL =103L

Pressure

(i)The force exerted by the gas per unit area of the container’s walls in all directions is known as pressure.

As a result , Pressure (P)=[Force(F)]/[Area(A)] =[Mass(m) × Acceleration(a)]/Area(A).

(ii) Kinetic energy(KE= ½(mv2)is responsible for the pressure exerted by a gas. As the temperature rises, the kinetic energy of the gas molecules rises. 

As a result,  Pressure of a gas  ∝ Temperature (T).

(iii) A manometer is used to measure the pressure of pure gas, while a barometer is used to measure the pressure of a mixture of gases.

(iv) There are two common types of manometers: 

(a) open-end manometers and (b) closed-end manometers.

(v) The pascal (Pa), the S.I. unit of pressure, is defined as 1 newton per meter square. It’s a fairly compact unit.

1Pa =1Nm-2=1 kg m-1s-2’

(vi) Gauge pressure refers to the pressure in relation to the atmosphere. Absolute pressure refers to the pressure in relation to a complete vacuum.

Gauge pressure + Atmospheric pressure equals absolute pressure.

(vii)The gauge pressure turns negative when the pressure in a system is less than atmospheric pressure. However, it is commonly referred to as a vacuum.

Temperature

(i) As the temperature rises, gases expand. When the temperature is raised twice, the square of the velocity (v2 ) rises twice as well.

(ii) Thermometers are used to measure temperature in centigrade degrees (C) or Celsius degrees. Fahrenheit (Fo) is another unit of measurement for temperature.

(iii) The kelvin (K) or absolute degree is the S.I. unit of temperature.

K=oC +273.

(iv) F and oC have a relationship as follows:

 (oC)/5=(oF-32)/9.

Boyle’s law

Boyle’s law describes the relationship between a gas’s pressure and volume at a constant temperature. The volume of a gas is inversely proportional to the pressure of a gas at a constant temperature.

The equation for Boyle’s law is:

V ∝ 1/P

Or

P ∝ 1/V

Or

PV = K1

V represents the gas volume, P represents the gas pressure, and K1 represents the constant. Boyle’s Law can be used to calculate the current pressure or volume of a gas and is also known as:

P1V1 = P2V2

Exemplifications of Boyle’s Law

Let us consider an example of a filled balloon. If you squeeze the filled balloon ,you will see that  the balloon shrinks . This shrinking of balloon can be explained by Boyle’s law. As pressure is applied to the filled balloon ,the volume of air inside the balloon gets decreased.

Another example is of  scuba diver who quickly moves upward from a deep zone to the surface of water which results in decrease in pressure .That means volume of gas molecules in scuba divers body increases  . This expansion of gas bubbles  is a risk to diver’s organs as they might get damaged  and it even cause death. 

One more example is of fish who comes from deep sea to the surface of water die  as dissolved gases present in their blood expands due to decrease in pressure  .

Conclusion

The study of gases allows us to understand the matter at its most fundamental level: individual particles acting independently, nearly completely free of interactions and interference.

What is the significance of Boyle’s law?

Boyle’s law is important because it describes how gases behave. It demonstrates unequivocally that gas pressure and volume are inversely proportional. When you apply pressure to a gas, the volume decreases while the pressure increases.