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The Particulate Nature of

Matter

The Particulate Nature of

Matter

Chapter1

Chapter1

2

contentscontentsYou will learn about:

•Properties of matter in the solid, liquid and gaseous states

•The Kinetic Particle Theory

•The inter-conversion of the states of matter

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states of matterstates of matterstates of matterstates of matter

water exist as three states of water exist as three states of mattermatter

gasgas

liquidliquidsolidsolid

• All substances are made of matter.

•The three states of matter are solid, liquid and gas

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Properties of matter in solid, liquid and gaseous states

Properties of matter in solid, liquid and gaseous states

SolidsSolids LiquidsLiquids GasesGases

Shape FixedNo fixed shape; take

the shape of container

No fixed shape; expand to take the shape of container

HardnessHard and is usually

made of crystalsNot hard and can

flow easily

Not hard. Can flow along a pipeline

and diffuse easily

Density High density medium density Low density

Compression No No Easily compressed

Volume Fixed FixedNo fixed volume; expand to fill the

container

Main Features of Solids, Liquids and Gases

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The Kinetic Particle TheoryThe Kinetic Particle Theory

The Kinetic Particle Theory states that all matter is made up of tiny particles, and these particles of matter are always in constant random motion.

The Kinetic Particle Theory states that all matter is made up of tiny particles, and these particles of matter are always in constant random motion.

•Scientists have gathered evidence from diffusion experiments, changes in volume and changes in states and hypothesized that matter is made up of small particles.

•The ancient Greeks were the first to suggest that everything is made up from particles. Thus, scientists came up with the Kinetic Particle Theory.

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particles of matterparticles of matterProperty Solid Liquid Gas

Diagrammatic representation of particles in

each state

Arrangement and Packing

between particles

Particles are in orderly

arrangement and are packed very closely together.

Particles are not in orderly

arrangement and is closely packed

together.

Particles are not in orderly

arrangement and are very far apart from one another.

Motion of particles

Particles vibrate about a fixed

position

Particles are free to move around the liquid and

slide over each other.

Particles are very far apart from each

other.

Forces of attraction between particles

Very strong forces of attraction

between particles

Strong forces of attraction

between particles

Very weak forces of attraction

between particles

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particles of matterparticles of matter

QuickTime™ and aCinepak decompressor

are needed to see this picture.

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Inter-conversion of states of matterInter-conversion of states of mattermeltingmelting

HEAT

temperature

stearic acid

water at 100ºCexperiment to find the

melting point of stearic acid

•When a solid is heated, particles gain kinetic energy and vibrate faster.

•At a certain temperature, particles would have gained enough energy to overcome the attractive forces holding the particles of solid together in fixed positions.

•Melting occurs. Particles now are able to move around the liquid and slide over one another.

Why is a water bath used?

Prevent direct heating

of combustible substances

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Inter-conversion of states of matterInter-conversion of states of matter

QuickTime™ and aCinepak decompressor

are needed to see this picture.

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changes of statechanges of statemeltingmelting

temperature (ºC)melting starts

temperature remains constant. Why?

melting completes

time from start (min)

melting point

(69°C)

SOLID

SOLID + LIQUIDLIQUID

Heat energy absorbed by the particles is used to overcome the forces of attraction holding the particles together in their fixed positions.

Graph of temperature vs time plotted to depict melting process

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changes of statechanges of statefreezingfreezing

• When a liquid is cooled, particles lose kinetic energy and move slower and come closer together.

•At a certain temperature, particles no longer have enough energy to move around the liquid.

•Freezing occurs. Liquid changes into a solid and particles can only vibrate in their fixed and orderly positions. Heat energy is given out during freezing.

•Freezing and melting points are the same for a pure substance.

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temperature remains constant.

Why?

freezing completes

freezing starts

freezing point (=melting point)

for pure substances

SOLID

LIQUID + SOLID

LIQUID

temperature (ºC)

time from start (min)

changes of statechanges of statefreezingfreezing

Heat loss due to cooling is exactly balanced by the heat energy liberated as the particles attract one another to form a solid.

Graph plotted to depict freezing

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changes of statechanges of state

boilingboiling

experiment to find the boiling point of 1,1,1-trichloroethane

liquidtrichloroethane

thermometer

condenserwater out

water in

boiling stones

HEAT liquid trichloroethan

e

• When a liquid is heated, the particles gain kinetic energy and move faster.

•At a certain temperature, particles throughout the liquid gain enough energy to overcome the forces of attraction holding them together in the liquid.

•Boiling occurs. Liquid changes into a gas. Particles are now able to move freely and randomly around at great speeds.

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changes of statechanges of state

boilingboiling

temperature (ºC)

time from start (min)

liquid is boiling between points A and B

A B

boiling starts at point A

0

74ºC

The temperature remains constant during boiling because the heat energy is absorbed by the particles of liquid to overcome the forces of attraction holding them together.

Graph plotted to depict boiling

A pure substance has a fixed boiling point at a fixed pressure. Boiling point increases when pressure increases (i.e. pressure cooker) and boiling point decreases when pressure decreases. (on mountain top)

Boiling occurs when the vapour pressure of the substance equals to the ambient pressure.

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changes of statechanges of stateevaporationevaporation

BoilingBoiling EvaporationEvaporation

occurs only at boiling pointoccurs at temperatures

below boiling point

takes place throughout the liquid

takes place at the surface of the liquid

very fast process very slow process

• occurs when liquids turn into gases without boiling.

•Evaporation occurs because some particles near the surface of the liquid have enough energy to escape as a gas.

•Liquids which vaporize quickly at low temperatures are called volatile liquids.

•Differences between Boiling and Evaporation:

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changes of statechanges of statecondensationcondensation

sublimationsublimation

• When a gas is cooled, particles lose kinetic energy and move more slowly. The particles come closer to one another.

•At a certain temperature, the particles no longer have enough energy to move about randomly at great speed.

•Condensation takes place. The gas is changed into a liquid. Heat energy is given out during condensation.

• Change of state from solid to gas without melting.

•Sublimation occurs because some particles have enough energy to break off from the solid and escape as a gas.

•Examples include iodine, ammonium chloride and solid carbon dioxide (dry ice)

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changes of statechanges of state

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are needed to see this picture.

sublimationsublimation

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meltingmelting

particlesparticles

energyenergy

has mosthas most

are close together in are close together in disorderly arrangement indisorderly arrangement in

liquidliquid

shape of shape of containercontainerhashas

boilingboilingare far apart and

are far apart and move at random in

move at random in gasgas

diffusiondiffusion

particles can particles can mix together bymix together by

particles can particles can mix together bymix together by

particles can move particles can move so liquids flowso liquids flow

becausebecause

compresscompress

can becan be

no shapeno shape

hashas

fixed shapefixed shape

hashas

energyenergy

has leasthas least

are close together in

are close together in

orderly arrangement in

orderly arrangement in

solidsolid

particles can particles can only vibrateonly vibrate

becausebecause

freezingfreezing

condensationcondensation

sublimationsublimation