Solids Liquids Gases of Matter.pdfFar apart. 20 Gases: KMT Random motion Straight line paths until...

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1 States of Matter Solids Liquids Gases

Transcript of Solids Liquids Gases of Matter.pdfFar apart. 20 Gases: KMT Random motion Straight line paths until...

Page 1: Solids Liquids Gases of Matter.pdfFar apart. 20 Gases: KMT Random motion Straight line paths until collision ... “Dynamic Equilibrium” ... Amorphous Solids Solids with no crystal

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States of Matter

Solids Liquids Gases

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Solid vs. Liquid vs. GasDepends on

Kinetic

Energy of

particles

Attractions

between

particles

vs

only two things: What?

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Intermolecular Forces

(Molecular Attractions)

Covalent molecules are attracted to

each other by “intermolecular forces”.

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are what “stick” one molecule to

other molecules (not the

bonds within one molecule)

are responsible for the solid

and liquid states for molecules

Intermolecular Forces

(Molecular Attractions)

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Dipole-dipole force

(dipole force)

Dispersion force

Hydrogen bond force

(a special dipole force)

van der

Waals

forces

3 Types:

Intermolecular Forces

(Molecular Attractions)

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1. Dipole-Dipole Force “Electrostatic” attraction

of polar molecules.

+ - + - + -

- + - + - +

+ - + - + -

For example: HF and H2O

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Dipole-Dipole

charged rod

Buret with

water

(+) (-)(-)

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Review: Polar Molecules

A molecule with only two atoms is

polar if the atoms have different

electronegativities.

H-Cl

polar

Br-Br

nonpolar

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Review: Polar Molecules

If more than 2 atoms in molecule:

•Draw dot structure

•If outside atoms are the same

and central atom has

no nonbonding electrons,

the molecule is nonpolar.

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Are These Polar(do they have a dipole force)?

CH4

H2

NH3

CH3Cl

SO2

NaCl

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2. Dispersion Force

All molecules have “instantaneous”

polarity due to the random motion

of the e- around the nucleus.

+ -

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Attractive force resulting

from the temporary dipoles

2. Dispersion Force

Responsible for condensation

of nonpolar gases

Is stronger the larger the

molecule (molar mass)

+ - + -

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The States of Halogens

At room temperature:

F2 and Cl2 :gases

Br2: liquid.

I2: solid.

Increased

molar mass

so

larger

dispersion force

All are nonpolar and have

only dispersion forces.

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3. Hydrogen Bond ForceA strong dipole-dipole attraction

between molecules when hydrogen

is bonded to N, O, or F

d- d+strong

H-bond force

……

Why?

F—H F—Hd- d+strong

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Hydrogen Bond

H—O H—O

H H

electronegative

F, O, or N atom

H-bond

from H to

lone pair

on O

H atom on

different

molecule

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Strength of Molecular

Attractions1. Dispersion Force

(weakest unless molecule is large)

2. Dipole Force

3. H-Bond Force (strongest)

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Name the Type of

Molecular Attractions

N2 NH3

CH4 H2O

HCl SO2

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Gases (KE >> attractions)

“Kinetic Molecular Theory”

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Gases: KMT

1.Gas “particles” (atoms

or molecules) are: Hard spheres

Insignificant volume

(compared to container)

Far apart

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Gases: KMT

Random motion

Straight line paths

until collision

Fill container

2. Gas “particles” are in

constant motion

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Gases: KMT

3. Gas particles have no

attractive forces between them.

(not 100% true!)

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Gases: KMT

4. Collisions are perfectly “elastic”

no energy lost

during collisions

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Gas

Mostly Empty SpaceCompare volumes in liters of:1 mole water vapor (gas)

vs.1 mole liquid water

Gas is >1000 times volume of liquid

22.4 L

0.018 L

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Gas Speed

Speed of O2 at 20 oC is

~1660 km/hr. WOW !!!

Why don’t you smell

perfume as soon as

someone enters a room?

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What keeps the walls of an

inflated balloon pushed out?

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Gas Pressure

Pressure = force /area

Gas molecules exert

pressure on the

walls of a container

due to collisions.

More molecules more pressure

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VacuumIf there are no gas

molecules, pressure is zero.

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What Will Happen?

plastic sheet

water

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Atmospheric Pressure

Collision of air molecules with

objects results in atm. pressure.

1.00 atm = ave. pressure at sea level

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Atmospheric PressureIs pressure higher or lower than

1 atm on top of Mt. Everest?

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Measuring Pressure

Vacuum

atm P760 mm Hg

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Measuring Pressure

1 atm = 760 mm Hg = 101.3 kPa

What is pressure in

atm. and kPa during

a hurricane if

P = 720 mm Hg?

(Table A)

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Gas Temperature

Molecules speed up

“Average kinetic energy”

(energy of motion) increases.

Temperature (K) increases

What happens when a gas

is heated?

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Kinetic Energy Distribution

low T (K)

high T (K)

NO!!!

kinetic energy

% m

ole

cu

les

100%

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Liquids

A “condensed” state of matter.

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Liquids

similarKinetic

Energy of

particles

Attractions

between

particlesvs

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Molecules in Liquid

in constant motion

not much affected by pressure

“touching”

held together by intermolecular

forces

can glide past each other (flow)

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Evaporation

Not

magic!

What happens to a glass of

water left overnight?

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Evaporation

kinetic energy

% m

ole

cule

s Energy to

break

intermolecular

forces

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EvaporationAfter some liquid evaporates, the

remaining liquid is cooler.

Why ?

The liquid warms again.

Why ?

Then more evaporates.

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Evaporation in

Closed ContainerVapor pressure:Pressure due to

evap. gas in closed

container.

open closedDepends on 2 things

Kinetic

Energy of

particles

Attractions

between

particlesvs

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“Dynamic Equilibrium”(closed container)

Liquid Vapor (gas)

At equilibrium:

rate evap. = rate cond.

evaporation

condensation

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Vapor Pressure

As T increases, vapor

pressure increases

(more KE)

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Table H: Vapor Pressure

VP depends only on:

substancetemperature

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Vapor PressureUsing Regents Table H:

What is VP of ethanol at 60oC?

At what T does VP of water

equal 50 kPa?

Which substance has greater

molecular attractions:

ethanol or water?

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Boiling Point (BP)

The temperature at which vapor

pressure equals external pressure.

“normal boiling point”

(BP at 1 atm.)

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Boiling

How do you know when

something is boiling?

What’s in the bubble?

What’s P in bubble?

Add heat energy to over-

come molecular attractions

(T doesn’t change!)

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What is Boiling Point of H2O:

in Endwell

where P = 1.0 atm?

in Denver

where P = 86 kPa?

on Mt. Everest

where P = 35 kPa?

Table H is also BP vs. Pressure!

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Boiling Point

Would it take longer or shorter

time to boil at egg in Denver

than in Endwell?

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Solids

Particles arranged in

regular, repeating

pattern called crystal

lattice.

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Comparison of K.E. to

Molecular Attractions

Gas: KE >> I.M. forces

Liquid: KE ~ I.M. forces

Solids: KE << I.M. forces

(only vibrations are possible)

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Melting

Solid Liquidmelting

freezing

Ionic compounds: high M.P.

NaCl: 801 oCNa+ Cl-

Molecular compounds: low M.P.

HCl: -112 oCHCl HCl

Break ionic bond

Break IM force

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diamond graphite “bucky-ball”54

Allotropes Different forms of the same state

of an element or compound.

Example: carbon

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Allotropes

Other examples:

Sulfur

O2 and O3

Red &

white phosphorous

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Amorphous Solids

Solids with no crystal structure

Examples:

plastic & rubber

asphalt

glass

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solid

Phase Diagram for H2O

Triple point

Temperature (oC)

Pre

ssure

(atm

)

liquid vapor

1

Normal

M.P.

Normal

B.P.

0 100

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Sublimation Substance passes from

solid directly to vapor.

See phase diagram below

“Triple Point”. examples:

dry ice (CO2)

iodine (I2) (demo)

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Lab 12 Analysis

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CuCl2 + Fe Cu + FeCl2vs.

3CuCl2 + 2Fe 3Cu + 2FeCl3DATA TABLE

Mass empty dry beaker_________

Mass iron nails (before rxn)______

Mass iron nails (after rxn)_______

Mass beaker & dry product______

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Warm-up

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List the three types of

molecular attractions.

What causes the “dispersion

force”? Which molecules have

this force?

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Warm-up

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Predict the shape of PCl3.

Is it polar?

What forces hold molecules of PCl3together?

What are the 4 assumptions of KMT?

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Warm-up

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Predict the shape of SCl2. Is it polar?

What forces hold molecules of SCl2together in the liquid state?

What is meant by

“kinetic energy distribution”?

What is pressure?

What is vapor pressure?

What is VP of H2O at 80oC? At 100oC?

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Warm-up

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Predict the shape of SCl2.Is it polar?

What forces hold molecules of SCl2together in the liquid state?

What is pressure?

Use KMT to explain why a

balloon gets smaller when cold.

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Warm-up

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What is “STP” ?

What molecular attractions hold ammonia

molecules (NH3) together?

What temp. will water boil at

if P = 620 mm Hg?

How can liquid water in underground

geysers be hotter than 100oC?

What is meant by “kinetic energy

distribution”?