liquid
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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
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