Gases

Question 3.1: What is matter? Also give its different states?

Answer: Anything (material in Nature) which has mass or weight and occupies space.

States of Matter: There are four states of matter, namely: Solid, liquid, gas and Plasma. Solid state is the most common state of matter. Liquid state is less common than other states of matter because it can exit within a relatively narrow range of temperature. The gaseous state is the simplest state of matter.

Question 3.1: Give important properties of gases liquid and solid.

Answer: Some general properties of gases are given below.

i. Volume and Shape: Gases have no definite volume and no definite shape. They acquire the ' volume and shape of the container.

ii. Density: They have very low densities as compared to solids and liquids.

iii. Diffusion: They can diffusx and effuse very rapidly.

iv. Compressibility: They can be compressed by a applying pressure because there are large empty spaces ' among gas molecules.

v. Expansion: They expand on heating and contract on cooling.

vi. Pressure: they exert pressure when they are closed in a container.

vii. Joule Thomson effect: Rapid expansion of gases causes cooling (Joule-Thomson effect).

Properties of liquids:

i. Volume and shape: Liquids have definite volume but no definite shape. They acquire the shape of the container.

ii. Density: Their densities are close to solids due to negligible intermolecular distance.

iii. Diffusion: They diffuse very slowly into each other because of slow motion of molecules.

iv. Intermolecular forces: The intermolecular forces are appreciable and have marked effect on Melting Point and Boiling point.

v. Kinetic energy: Liquid molecules pass kinetic energy due to their motion. The change in kinetic energy may change at phase of the liquid.

vi. Collisions: molecules of liquid exchange energy due to their collision with one anther.

vii. Compressibility: liquids are almost incompressible due to close proximity of molecules.

Properties of Solids

i. Compressibility and density: The particles are tightly packed in solids. So they are incompressible and have high densities.

ii. Diffusion: Solids cannot diffuse into each other because of translational motion is not possible.

iii. Volume and shape: The particles of solid are held together by strong attractive forces and are regularly arranged. So solids have definite shade and volume.

iv. Vibrational motion: The solid particles possess vibrational motion.

Question 3.1: What do you mean by Gas laws?

Answer: All gases expand on heating and contract on cooling. AIl gases can be compressed by increasing pressure. The behavior of gases towards change in there volume and molar quantities has been generalized in the form of laws. They are called gas ' laws

Question 3.1: State and explain Boyle's law?

Answer.

Statement: ''The volume of a given mass of a gas is inversely proportional to its pressure at constant temperature”. Mathematically,

V=1/P (at constant temperature)

or PV = k

where P = pressure of gas V = volume of gas, k = constant

Similarly, it can be shown that P₁V₁ = k, P₂V₂ = k and so on

This gives another definition of Boyle's law:

“The product of a pressure and volume of a given mass of a gas remains constant at constant temperature.”

Continued

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