STATES OF MATTER

First, a few important things:

•Arrangement and movement of particles in matter determines the phase

•There are FORCES OF ATTRACTION between these particles that determine properties like shape that help distinguish between different phases

Describing the States of Matter

• Materials can be classified as solids, liquids, or gases based on whether their:– Shapes and volumes are definite

(does not change) or – Variable (does change).

Shape & Volume

•Some materials have a definite shape and volume, some do not.•SHAPE and VOLUME are clues to how the particles within a material are arranged

•http://www.harcourtschool.com/activity/states_of_matter/

GASLIQUIDSOLID

Solids

• Solid: the state of matter in which materials have a definite shape and a definite volume. – definite means shape and volume will

NOT change if you move it from a desk drawer to a backpack

– definite does NOT mean that the shape or volume can never change• For example: change shape of pencil when

you sharpen it

Solids

• Example: Copper wire• Arrangement of atoms:

– atoms are packed close together– arranged in an regular pattern (almost

all solids have some type of orderly arrangement of particles) page 69, fig.2

Liquids• Liquid: the state of matter in

which a material has a definite volume and a variable shape. – A liquid always has the same shape

as its container and can be poured from one container to another

Liquids• Example: mercury is a liquid at room

temperature– Arrangement of atoms

• atoms are close together

• Arrangement more random than that of a solid (page 69, fig. 3)

Gases

• Gases: the state of matter in which a material has neither a definite shape nor a definite volume – As gas takes the shape and volume of

its container

Gases

• Example: air (mixture of gases), natural gas (used for heating), helium (gas found in balloons)– Arrangement of atoms:

• atoms have more space between them than in solid/liquid form

• Not arranged in a regular pattern (very random, free to move)

Other States of Matter

• Plasma: found when a gas is heated to a temperature near 10,000 degrees Celsius                                                        – Occurs on Earth mainly in lightening

discharges and fluorescent lights– Found most commonly in the universe (Sun

and other stars) – TV’s?

Other States of Matter

• Amorphous Solids: lack the orderly/rigid internal structure found in crystalline solids; "moves" over time – Examples: rubber, asphalt, and

glasses

Other States of Matter

• Bose-Einstein condensate (BEC)– Bose and Einstein predicted this state

of matter in the 1920’s.– First observed in 1995.– Occurs near absolute zero, 0K– Atoms “clump” together and act as

one giant particle.

Kinetic Theory

• Kinetic Theory: states that all particles of matter are in constant motion

• Kinetic Energy: the energy an object has due to its motion– This is why, under ordinary conditions,

copper is a solid, mercury a liquid, and helium a gas

– Faster an object moves = greater kinetic energy (abbreviated KE)

Explaining the Behavior of Gases

• Motion in Gases: – There are forces of attraction among

the particles in ALL matter. – Particles in a gas are NEVER at rest– Atoms move in a straight line until it

collides with another atom or with a wall of the container

Explaining the Behavior of Gases

• What happens when 2 atoms collide:– One atom may lose KE and slow down– The other atom gains KE and speeds

up– TOTAL KE energy of the 2 atoms

remains the SAME

KINETIC THEORY OF GASES:

• The constant motion of particles in a gas allows a gas to fill a container of any shape or size.

• Kinetic Theory as applied to gases has 3 main points.

KINETIC THEORY OF GASES:1. Particles in a gas are in constant,

random motion2. The motion of one particle is unaffected

by the motion of other particles unless the particles collide

3. Forces of attraction among particles in a gas can be ignored under ordinary conditions

– WHAT?!?! WHY?!?! You were just told there were forces of attraction among the particles in ALL matter

 EXPLAINING THE BEHAVIOR OF

LIQUIDS • A liquid takes the shape of its

container because the particles in a liquid can flow to new locations. 

• The volume of a liquid is constant because the forces of attraction keep the particles together.

 EXPLAINING THE BEHAVIOR OF LIQUIDS

• Tug-of-war between the constant motion of particles and the attractions among particles– Think of trying to walk down the hall

between classes– Forces of attraction LIMIT the motion

of particles in a liquid, the particles in a liquid CANNOT spread out and fill a container

EXPLAINING THE BEHAVIOR OF SOLIDS • Solids have a definite volume and

shape because particles in a solid vibrate around fixed locations

• Particles in a solid = polite audience in a movie theatre– Movie is running, people stay in their

seats– People move within their seat but each

person remains in essentially the same location during the movie - they have "FIXED" locations

EXPLAINING THE BEHAVIOR OF SOLIDS • Vibration = repetitive back-and-forth

motion– Strong attractions among the atoms

restrict their motion and keep each atom in a fixed location relative to its neighbors

– Each atom vibrates around its location but DOES NOT exchange places with a neighboring atom

3.2 – The Gas Laws

Pressure

• Pressure: the result of a force distributed over an area– The smaller the area of impact is, the greater

the pressure produced– Example: walking on a frozen pond (bad ice)

• Snow shoes or tennis shoes?

• SI unit for pressure is the Pascal (Pa) or N/m2

Pressure

• Objects do not have to be large to exert pressure:           – Helium atoms in a balloon are constantly

moving– Pressure from a single helium atom is small– But, there are 10^22 helium atoms in a small

balloon!!!– That many small collisions will produce

noticeable pressure!

Pressure• Collisions between particles of gas and the

walls of a container cause pressure– More collisions = greater pressure– Speed and mass also affect pressure

Factors Affecting Gas Pressure

• Factors affecting pressure of gas in a closed container are:– Temperature– Volume– The number of particles in the container

Temperature & Gas Pressure

• Raising the temperature of a gas will increase its pressure if the volume and the number of particles are constant

Increase Temperature = Increase Pressure

T P

Temperature & Gas Pressure• Explains why pressure in tires increases after

time spent driving...– Constant motion of tires causes air inside to warm up– As temperature rises, KE of the particles increases– Increased KE causes the particles to move faster and

collide more with the inner walls of the tires– Increased number of collisions and increased force

of impact causes the pressure in the tires to rise

Volume & Gas Pressure

• Reducing the volume of gas increases its pressure if the temperature of the gas and the # of particles are constant

Decrease Volume = Increase Pressure

V P

Breathing…

• This relationship shows what happens to the volume and pressure in your lungs when you breathe

Inhaling

• Diaphragm contracts

• Contraction causes the chest cavity to expand

• Increase in volume causes the air particles to spread out, lowering the pressure inside

• Now the pressure of the air outside your body is greater than inside

• This causes air to rush into your lungs

Exhaling

• Diaphragm relaxes

• Volume of chest cavity decreases

• Particles of air are squeezed into smaller volume, pressure inside increases

• Pressure is greater inside the chest cavity so the air is forced out

Particle Number & Pressure

• Increasing the number of particles will increase the pressure of a gas if the temperature and volume are constant

Increase Particle Number = Increase Pressure

P# P

Balloon Bursting• This relationship explains why a balloon will

burst if you blow too much air into it...– The more particles of air in the same volume will

cause more collisions, which increases pressure– Eventually, the rubber cannot withstand the pressure

and bursts!

Charles’ Law(proportional, same)

• Charles' Law states that the volume of a gas is directly proportional to its temperature (Kelvin) if the pressure and the number of particles are constant

Charles’ Law

Charles’ Law

• There is a direct relationship between volume and temperature– If temperature increases, volume increases– The temperature needed to produce a volume of

0 mL = 0 Kelvin = absolute zero = -273 degrees Celsius

• Absolute zero has not yet been reached!

Charles’ Law

Boyle’s Law(inverse, opposite)

• Boyle's Law states that the volume of a gas is inversely proportional to its pressure, if the temperature and number of particles are constant

Boyle’s Law

Boyle’s Law

Boyle’s Law

• The relationship is opposite for pressure and volume, as one increases, the other decreases!

• Example: squeezing a balloon...

Boyle’s Law

P1V1 = P2V2

Combined Gas Law

• Describes the relationship among the temperature, volume and pressure of a gas when the number of particles is constant

• It describes the relationship between Charles' Law and Boyle's Law

Combined Gas Law

3.3 Phase Changes

Phase Change

• Phase Change: reversible physical change from one state of matter to another

• There are 6 common phase changes: • Melting

• Freezing

• Vaporization

• Condensation

• Sublimation

• Deposition

Refer to page 85, figure 16 for more detail

Phase Changes

Phase Changes

• During a phase change, the temperature DOES NOT change!!!– During a phase change, energy is transferred

between a substance and its surroundings.– Energy is either absorbed or released during a

phase change.

• Summarize the figure that follows

Energy Transfer

• There are two types of energy transfer:

1. Endothermic

2. Exothermic

Endothermic

• Endothermic: the system ABSORBS energy from surroundings – Example: melting– The amount of energy absorbed depends on the

substance

• Heat of Fusion: the amount of energy absorbed– Example: heat of fusion of water as it melts =

334 joules

Energy is Conserved

• Did you know...– As water freezes, it releases 334 joules of

energy to its surroundings– As water melts it absorbs 334 joules of energy

• The amount of energy absorbed as water melts is the same as the amount of energy released as water freezes: it is CONSERVED!

Exothermic

• Exothermic: system releases energy to its surroundings

• Example: Farmers spray water on crops when temperatures are expected to fall below freezing– The freezing of the water releases heat, which

helps protect the crop

Energy…absorbed or released?

Melting

• Solid Liquid

• Arrangement of molecules becomes less orderly as a substance melts

• Endothermic process

Melting

• Strong attractive forces in ice keep molecules in fixed positions– When removed from freezer, heat flows from air to

ice– Molecules heat up and gain energy = vibrate more

quickly– At 0 degrees Celsius some molecules gain enough

energy to overcome attractions and break free– When all have enough energy to move, melting is

complete

Freezing

• Liquid Solid

• Arrangement of molecules becomes more orderly as a substance freezes

• Exothermic

Freezing

• When liquid is put in a freezer, energy flows from water to air– Kinetic energy of molecules decreases = move

slower– Slower movement allows attractive forces to

have an effect– When all molecules are orderly, freezing is

complete

Liquid Solid

melting

FREEZING

Solid

Liquid

Gain in heat

Loss in heat

Vaporization• Liquid Gas

• A substance must ABSORB energy in order to change from a liquid to a gas (ENDOTHERMIC)

• As a substances vaporizes the particles become less orderly

• Heat of Vaporization: one gram of water gains 2,261 joules of energy when it vaporizes– heat of vaporization varies from substance to

substance

Vaporization

• Two vaporization processes have been distinguished:– Evaporation– Boiling

Evaporation

• You go outside after a rain shower on a sunny, warm day you might notice puddles. 

• If you return to the same location a few hours later, the puddles are gone.  This shows evaporation.

Evaporation

• Evaporation: process that changes a substance from a liquid to a gas at temperatures below the substance's boiling point– Molecules near the surface are moving fast

enough to escape the liquid and become water vapor

– The greater the surface area the faster the water evaporates

Vapor Pressure• Vapor Pressure: the pressure caused by the

collisions of particles in a vapor with the walls of a container (closed container)– as water evaporates, water vapor collects above the

liquid– vapor pressure increases as the temperature increases

Vapor Pressure

Boiling

• Particles become less orderly

• As you heat water, both the temperature and the vapor pressure of the water increase

• Vapor pressure = atmospheric pressure = water boils

Boiling• Kinetic Theory explains what happens when

water boils:– as temperature increases, water molecules move

faster and faster– temperature reaches 100 degrees Celsius some

molecules below the surface of the liquid have enough KE to overcome the attraction of neighboring particles

– boiling point depends on the atmospheric pressure

Effect of Pressure On Boiling Point• Lower pressure would lower the boiling point of water.• Water will boil very quickly on the mountain top but the

temperature reached is lower than 100oC.• Increasing pressure would raise the boiling point of water.• Water will boil at a higher temperature above 100oC.

Normal Boiling Point• Boiling point of a liquid at a pressure of 101.3 kPa – or standard pressure

Condensation• Gas Liquid

• During this process particles in a substance become more orderly

• Exothermic

Condensation• Condensation: the phase change in which a

substance changes from a gas or vapor to a liquid

• Ever notice after a shower your bathroom mirror has "clouded" over?– This "cloud" on the mirror is caused by water

vapor that cooled as it came in contact with the mirror

– Process also responsible for the morning dew on the grass

evaporation

CONDENSATION

Vapor/gas

LiquidGain in heat

Loss in heat

Vapor Liquid

Sublimation

• Solid Gas

• During this process particles become less orderly

• Endothermic

Sublimation

• Sublimation: phase change in which a substance changes from a solid directly to a gas or vapor

• Dry Ice (used sometimes in concerts and plays to create a fog-like special effect)– Dry ice is common name for solid form of

carbon dioxide– At room temperature it changes from a solid to

a gas

Sublimation (Dry-Ice)

Deposition

• Gas Solid

• During this process particles become more orderly

• Exothermic

Deposition

• Deposition: phase change in which a substance changes from a gas directly to a solid – Causes frost to form on windows - water vapor

in the air contacts cold glass, the water vapor loses enough KE to change directly from a gas to a solid

Gas Solid

sublimation

deposition

Solid

Gas

SKIPS LIQUID PHASE

Gain in heat

Loss in heat