Chapter 2a Matter

8/8/2019 Chapter 2a Matter

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Why can the smell ofdurians be detected even

very far away ?


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When a drop of oil is

placed on the surface of

water, the oil spreads out.

Why?


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Chapter 2

The

Structure

of the

Atom


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Matter

Matter is anything that

occupies space &has mass.

Is air an example of matter ?


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Matter

Element Compound

Atom Molecule Molecule Ion+ -


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Element Substance that consists

of only ONE type

of atom. Pure substance that cannot be

broken down into simpler

substances by physical /chemical processes.


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Compound

Substance that

contains TWO ormore elements

that are chemicallybonded together.


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Matter is made up of

tiny & discrete particles.

There are spaces

between

these particles.


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These particles may

be atoms,

molecules or

ions.


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An atomis the smallest particle

of an element.

Metals, noble gases, carbon exist

as atoms.


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A molecule is a group of

two or more atoms

which are chemically

bonded together.

oxygen gas, water are examplesof molecules.


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An ion is a

positively-charged

ornegatively-charged

particle.

Table salt consists of one ionNa+ & one ion Cl-


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Particles in matter are

in motion.

Diffusion occurs when particles of

a substance move in between theparticles of another substance.

Diffusion of matter occurs most

rapidly in gases, slower in liquids

& slowest in solids.


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Rate of diffusion depends

on theirmasses.

Gas with low molecular mass

diffuse faster than those with high

molecular mass. The rate of diffusion is affected by

the temperature.

The higher the temperature, the

faster the particles move & so the

faster the diffusion.


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The Kinetic Theory ofMatter

State Solid Liquid GasArrange-

ment of

particles packed packed very far

closely slightly apart from

together loose each other

in an & not in and in

orderly an orderly random

manner. manner. motion.


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State Solid Liquid GasMove- vibrate & vibrate, vibrate,

ment of rotate rotate & rotate &

particles about the move move

fixed throughout freely.

position. the liquid, Rate of

collide collision

each other. greater

than liquid


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State Solid Liquid GasForces strong strong, weak

of but weaker

attraction than the

between forces in

particles solid.


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State Solid Liquid GasEnergy Low higher highest

content

of

particles


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State Solid Liquid GasVolume fixed fixed not fixed

cannot cannot be can be

be compressed compressed

compressed easily easily

Shape fixed not fixed not fixed

but takethe shape

of the

container


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Changes in states of matter

Solid

Sublimation melting

Sublimation Freezing

Condensation

Gas LiquidBoiling

heating cooling


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Changes in states of matter

are caused by heating /

cooling.

The kinetic theory of matteris

used to explain the changes in

states of matter.


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Melting

When a solid is heated,particles gain kinetic energy

& vibrate more vigorously.

As the temperature increases, particlescontinue to gain more energy until it is

able to overcome the forces that hold

them at fixed position.

At this point, the solid becomes a liquid.


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Melting point can be used

to test the purity of substance.

Each pure substance has its

own definite melting point.

An impure substance melts over a

range of temperatures that is lower

than the melting point of puresubstance.


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Boiling

When a liquid is heated,

particles gain kinetic energy &

move faster as the temperature

increases. Eventually, particles have enough

energy to break the forces that holding

them together. Particles are now able to move freely &

far apart. A gas is formed.


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What is Evaporation ?

Compare & contrastthe boiling &

the evaporation processes.


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Boiling Evaporation

Occurs in the entirebody of liquid

Occurs at the surfaceof the liquid

Occurs only at boiling

point

Occurs at any

temperature


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Condensation

When a gas is cooled, particles

lose energy & move slower.

Eventually, the movements of particles

become slow enough for the gas tochange into a liquid.

Particles attract one another to form a

liquid.


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Freezing

When a liquid is cooled, particles

lose energy & move slower.

As temperature decreases, particlescontinue to lose more energy until they

do not have enough energy to movefreely.

Forces formed to hold the particles

together. At this point, the liquid change into a

solid.


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Sublimation

A process by which a solid

changes directly into a gas

without passing through the liquid

state & vice versa. Substances that undergo sublimation

are iodine, ammonium chloride (NH4Cl),

dry ice (solid carbon dioxide) &naphthalene.


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Change of

state

Change in energy

Solid liquid

Liquid gas

Solid gas

Heat energy is

absorbed

( endothermic )

Liquid solid

Gas liquid

Gas solid

Heat energy is

released

( exothermic )


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At pointA, naphthalene exists

as solid.

When the solid is heated, heat

energy is absorbed. Particles gain kineticenergy & vibrate faster. Temperature

increases from point A to point B. At B, solid begins to melt. Temperature

does not rise even though heatingcontinues. Temperature remains constantbecause the heat absorbed is used toovercome the forces between particles.During this stage, both solid & liquid arepresent.


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At C, all the solid has melted.

From C to

D, particles in liquid

absorbed heat energy & move

faster. Temperature increases.


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At E, naphthalene exists as

liquid. When the liquid is cooled, particles

lose kinetic energy & move slower.

At F, liquid begins to freeze. Temperatureremains constant because the heat loss to

the surroundings is exactly balanced by the

heat energy liberated as the particles attract

one another to form a solid.At thistemperature, both solid & liquid are present.


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At G, all the liquid has frozen.

From G to H, particles in solidrelease heat energy & vibrate

slower. Thus the temperature decreases.


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During the heating of naphthalene,

water bath is used to ensurethat the naphthalene is heated

evenly. Furthermore, the naphthalene

is highly flammable. For solid with melting point above 100

C, liquid with higher boiling point than

water such as oil must be used. The naphthalene is stirred

continuously to ensure an evenheating.


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During the cooling of naphthalene,

the boiling naphthalene is placedin a conical flask. The air trapped

in the conical flask is a poor conductor

of heat. This helps to minimize theheat loss to the surroundings which

may affect the accuracy of the freezing

point obtained.


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The naphthalene is stirred

continuously to avoidsupercooling.

Supercooling is a condition in which

the temperature of the cooling liquiddrops below its normal freezing point,

without the appearance of a solid.

The melting point & freezing point ofnaphthalene are the same, that is

80 C.


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To forgive othersis to be

good to oneself.~ Still Thoughts

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Chapter 2a Matter