LIQUID

Introduction

Molecules in liquid are closed to one another, attractive forces are stronger (keep molecules together) compared to gases.

Can move past one another freely (flow, poured)

Take the shape of a container.

Almost incompressible

Viscosity (its resistance to flow) – is affected by size & intermolecular forces. Complex, polar molecules: have high viscosity.

Increase T viscosity will decrease

Mercury is viscous liquid

Surface tension : force that cause the surface area of liquid to contract (responsible for spherical shape of liquid drop).Molecule that have a high surface tension is………….?

Decrease with an increase in temp. or decrease in polarity.

Cohesive : intermolecular forces holding a liquid together.Adhesive forces : forces of attraction between a liquid and surface.

Diffusion – Spreading of liquid or gas into a region where it is originally not present.

Liquid diffuses slower compare to the gas (stronger force between molecules).

Liquid Vapour

Vaporization – change of liquid to gas. A few high-energy molecules which possess sufficient energy to overcome the attractive forces and escape from the bulk liquid (convert to gas).

Condensation : conversion of a gas or vapour to liquid. A fraction of gaseous molecules lose energy and return to liquid state.

Liquid in an equilibrium state : rate of vaporization = rate of condensation

vaporization

condensation

Vapour Pressure – pressure exerted at the equilibrium state of a liquid Affected by its intermolecular forces and temperature.

1) intermolecular forces :

Vapour pressure high if intermolecular forces are weaker

Weaker intermolecular forces more volatile low boiling point

Stronger intermolecular forces non volatile higher boiling point

2) Temperature : Vapour pressure increase if temp. increase (rate of motion increase).

Boiling of liquids

Process in which vaporization occurs throughout a liquid.

Boiling point = temperature at which the vapour pressure is equal to external atmospheric pressure.

Not constant, depend on the atmospheric pressure and the nature of the attractive force between the liquid molecules.Higher atmospheric pressure : boiling point increase.Stronger intermolecular forces (or polar liquids) => higher boiling point.

Normal boiling point = temperature at which the vapour pressure is equal to 1 atm.

Introduction

Particles are closely arranged and touch one another – can only vibrate in a fixed position (fixed volume, shape and incompressible).

Has high density.

Divided into crystalline solid and amorphous solid

crystalline solid have a regular three-dimensional arrangement, occupy fixed position. e.g.. NaCl

amorphous solid have random arrangement or un orderly arrangement e.g. rubber & plastics

Phase Changes in Solid

Heating – particles vibrates and solid melts (enough energy to break away from interparticle forces.

Molecules move freely ( Solid Liquid).

Melting point : temp. at which the solid and liquid phase coexist in equilibrium.

Freezing point : the temp. at which the liquid and solid phase coexist in equilibrium.

Cooling – particles of liquid lose energy, move closer and arrange to fixed position. (Liquid Solid).

Sublimation – direct transformation of solid into gas, without going through liquid phase.

Deposition – direct transformation from gas into solid during a cooling process.

TYPE OF SOLIDS

Ionic solids particles made up of cation and anion respectively, which are

alternatively arranged in three dimensions and are held strongly by electrostatic forces ;eg NaCl

Giant covalent solids (Macromolecule crystals)consist of particles held together by covalent bonds, non- metals. e.g.. Graphite, diamond, silicon.

Molecular covalent solidsparticle consists of simple molecules which are held together by weak van der Waals forces (Has very low melting and boiling point). e.g.. I2 and P4.

Metallic solids atoms of the same metal which are bound together by metallic bond (strong force of attraction between the positive ions and delocalized electrons). e.g.. Iron and titanium.

Gas Laws

Boyle,s Law P1V1 = P2V2

Charles's Law V1/T1 = V2/T2

Avogadro's Law V1/n1 = V2/n2

Ideal gas equation PV = nRT

Combined gas Law P1V1 / T1= P2V2 / T2

SUMMARY

Dalton’s Law of partial pressure

PTotal = P1 + P2 + P3 +P4 + …….+Pn

= (nX + ny + nz) (RT) V

Mole fraction of gas : Xx = nx /n total = Px/Ptotal

van der Waals equationP + n2a (V- nb) = nRT

V 2