UNIVERSITY OF WAHCourse code: EDU-116

Topic: “GASEOUS STATE OF MATTER”

Submitted To: Ma’am UzmaSubmitted By: Muhammad Usama Nawaz Reg # 055 BS-CHM-4th-(Section-A)

1-Previous Knowledge Testing:

What is matter?

Ans:•Matter is anything that has mass and takes up space.• Matter occurs in three states: solids, liquids, gases.•Examples of solids include ice (solid water), a bar of steel, and dry ice (solid carbon dioxide). •Examples of liquids include water and oil. •Examples of gases are air, oxygen, and helium.  

Where is matter found?

Ans:Matter is found everywhere anything you touch or see is matter.

Which gas is present in largest amount in atmosphere?

Ans:Nitrogen(78%)

Introduction:At room temperature, most of pure substances exist in any of the three states of matter gas, liquid or solid. The earth atmosphere is the mixture of gases. It not only support life but also accommodates exhaust gases.Therefore,it is important to understand the behaviour of gases.

Announcement of the topic:Today we are going to read about , “GASEOUS STATE OF MATTER” .

1-TYPICAL PROPERTIES:

Diffusion:The movement of molecules from

higher concentration to lower concentration is called diffusion. Molecules in a gas are widely separated and they do not have any attractive or repulsive forces. Thus molecules of one gas can move easily between the molecules of another gas.

Effusion:When a gas is allowed to pass through a

hole of the size of a molecule that only one molecule at a time can pass through the hole. The escape of gas molecules through the hole one after the other without collision is called effusion.

Pressure:Force exerted by a gas on unit area of container is

called its pressure. for example you can see it when you blow a balloon.

At sea level, the atmospheric pressure is 760 mm of Hg or 760 torr.(1 mm of Hg= 1 torr)

1 atm = 760 mm of Hg = 760 torrThe system international unit of pressure is

Pascal(Pa) which is very small unit. So, that kilopascal(Kpa) is used for atmospheric pressure.

1 atm = 101.325 Kpa = 1.01325(10⁵) PaSo,1 atm=760 mm of Hg=760 torr= 101.325 Kpa =

1.01325(10⁵) Pa

Compressibility:Gases are highly compressible. This is due to the

presence of large empty spaces between the gas molecules. On applying pressure, distance between the gas molecules decrease, therefore, its volume decreases.

Mobility:

• Gases can flow and can be transported through the pipes over long distances but it can also leak more rapidly out of a small hole. This is due to the tendency of a gas to expand and fill the entire available space.

Density:Gases have relatively low densities under

normal condition. This is because the molecules are much farther apart in the gas.

When a gas is cooled, its density increases because its volume decreases.

Temprature Density(g/dm³)

20˚C 1.4 of oxygen

0˚C 1.5 of oxygen

2-Effect on the volume of a gas by change in temprature and pressure:1-According to kinetic molecular theory of

gases, gas molecules are in constant random motion. They move in straight line until they collide with another molecule or the walls of container.

The pressure a gas exerts in a container is due to the force exerted on the walls of container. There are large empty spaces between the molecules . So, by increasing pressure, the volume of the gas decreases.

2- When temprature increases at constant pressure the average kinetic energy of gas molecules increases. So, molecules hit the walls more energetically and volume of the gas increases.

3-Laws related to gases:

Boyel’s Law:The volume of given mass of a gas at constant temprature is inversely proportional to the pressure on the gas. It states that, “the volume of fixed amount of a gas at given temprature is inversely proportional to the pressure”. P α 1/V P=1/V×constant PV= constantThis means that product of volume and pressure must constant if inverse relation exist between them.

Pressure-Volume Relationship: Pressure(atm) Volume(L) PV(atm.L)

1 1 12 0.5 1

Charles’s law:It states that ,“the volume of given mass of a

gas varies directly with absolute temprature at constant pressure”.

V α T V=constant(T) V/T=constantSo the ratio of V/T remains constant at

constant pressure.

Volume-Temprature Relationship:Temprature (K) Volume(dm³) V/T

200 0.5 0.0025

400 1.0 0.0025

RECAPTULATION:

What is pressure?Explain the boyel’s law?What is the effect of temprature on density of a gas?