Properties of Gases: Overview and Sample Questions

Gas is one of the three fundamental states of matter. Apart from the other two fundamental states, gases do not have any definite shape, size, or volume. The Matter is divided into solid, liquid, and gas according to the amount of energy embedded in each particle, Gas particles have a high amount of energy embedded in them.

Keyterms: Gas, Liquid, Gas, Energy, Velocity, Intermolecular force, Kinetic Energy, Molecules

Read More: Kinetic Interpretation of Temperature

---

Gases, an overview

[Click Here for Sample Questions]

Gas is a unique state of matter in which the molecules are far apart from each other and they are constantly in motion with high velocity. Gases do not have any definite size, shape, and volume on their own, the volume of gas is equal to the volume of the container in which it is contained. The attractive force present between the molecules of a gas is called Intermolecular forces. The gases in which the intermolecular force of attraction is zero are considered ideal gases.

In ideal gases, the molecules move with high velocity and as a result, all particles will very much be apart from the nearest particle, which in turn diminishes the intermolecular force. In general, real gases at high temperatures and low pressure tend to be ideal in nature. As the temperature increases, the kinetic energy also increases, which causes the weakening of intermolecular force.

Read More: Kinetic Molecular Theory of Gases

---

Properties of Gases

[Click Here for Previous Year Questions]

Gas being a unique fundamental state of matter shows many physical and chemical properties. Let us take a look at the major ones among them. The weak intermolecular force of attraction between particles attributes to the peculiar physical properties exhibited by the gases.

Pressure

The pressure exerted by the gas particles on the container enclosing it is defined as the force per unit area of the wall of the container. Since the gas molecules are in continuous motion, they will always exert pressure on the inside walls of the container. The amount of pressure exerted depends on the volume of the container and the temperature present. The pressure exerted by the gas molecules will be equal at all sides of the container.

Low density

The weak intermolecular force of attraction present in gases accounts for their low density. Since the particles are highly scattered in a gas, the Mass/Volume ratio will be of very low value due to the bigger value of volume.

Indefinite shape or volume

Gas particles are always in random motion with high velocity, thanks to their kinetic energy. The shape or volume of gas is the same as the shape of the container enclosing it. If the container is spherical, then gas will have a spherical shape. The shape of gas is affected by the temperature present and the pressure applied to the gas.

Expandability and Compressibility

The low intermolecular forces between particles contribute to the expandability and compressibility of gases. In the presence of high temperature and low pressure, the intermolecular force weakens further and the gas expands. Also when low temperature and high pressure are applied, gas compresses due to increasing intermolecular forces.

Diffusivity

Gases are highly diffusible substances. The large space present between molecules diminishes the difficulty of diffusion among two gases. A homogenous mixture is always obtained as a result of diffusion between two gases. The process of diffusion is also dependent on the conditions like pressure, temperature, and composition.

Read More:

---

Things to Remember 

• Gas is one of the three fundamental states of matter. Apart from the other two fundamental states, gases do not have any definite shape, size, or volume.
• The properties of gases are indefinite pressure, low density, shape and volume, compressibility, expandability, and diffusivity.
• Gas is a unique state of matter in which the molecules are far apart from each other and they are constantly in motion with high velocity. 
•  The attractive force present between the molecules of a gas is called Intermolecular forces.
• The gases in which the intermolecular force of attraction is zero are considered ideal gases.
• Gases have the weakest intermolecular force of attraction among the three fundamental states of matter.
• Gases do not have a definite shape or volume.
• Gases are easily compressible and expandable.
• In ideal gases, the intermolecular force of attraction is considered zero.
• Due to the presence of large intermolecular spaces, gases are highly diffusible.

---

Previous Year Questions

• According to the kinetic theory of gases… (JEE Advanced 2011)
• According to kinetic theory of gases, molecules of a gas behave like…
• The kinetic theory of gases gives the formula…
• According to the kinetic theory of gases, in an ideal gas… (AIEEE 2003)
• According to kinetic theory of gases, for a diatomic molecule… (JEE Advanced 1991)
• The average kinetic energy of gas molecules at… (AIIMS 1999)
• The root mean square velocity of the molecules in a sample… (Haryana PMT 2011)
• When the universal gas constant (R) is divided by…
• The internal energy of one mole of ideal gas is… (BHU 1995)
• Two perfect gases at absolute temperatures T1 and…
• A real gas behaves as an ideal gas… (JIPMER 2014)
• The temperature of one mole of an ideal gas increases… (COMEDK UGET 2012)