chapter 13 states of matter. kinetic energy = energy of motion kinetic theory = all matter consists...

Chapter 13 States of Matter

• Kinetic Energy = Energy of motion

• Kinetic Theory = all matter consists of particles in constant motion

Average Kinetic Energy• at any given temperature the particles of all

substances have the same average kinetic energy

• No kinetic energy = no movement = absolute zero

• Absolute zero = -273.15oC or 0 K (Kelvin)

Temperature vs. Heathttp://youtube.com/watch?v=rU-sPzshVnM

Let’s Learn:

How heat spreads from one region to another.

Examples:

How the whole copper rod get hot when we heat one end

How does the heat spread throughout the whole pot of water when we are only heating the bottomHow does the heat from the Sun reaches us

What Happens???• All things are made up of particles• When things get heated, they absorb heat

energy.• This means that the particles are absorbing the

heat energy With more energy, the particles are able to move faster

• When the particles move faster, the temperature of the object increases.

• Temperature increase means the object gets hotter.

Three Processes of Heat Transfer

• Conduction

• Convection

• Radiation

CONDUCTION• Occurs mainly in solids• Two types of conduction

Molecular vibrationFree electron diffusion

Note: Conduction is not the main form of heat transfer in liquids and gases because their molecules are spaced further apart.

Molecular Vibration

•When heat is supplied to one end, the molecules at the hot end start to vibrate more vigorously.

•In the process, they ‘bump’ into their neighboring molecules. In doing so, some energy is transferred to the neighbor.

•The neighbor molecule gains energy and starts to vibrate more vigorously. The cycle continues.

Conduction Animation

http://www.scienceonline.co.uk/flash/solid.html

http://www.bbc.co.uk/schools/gcsebitesize/physics/energy/energytransferrev6.shtml

Free Electron Diffusion

•This form of conduction takes place only in metals. As only metals have free electrons.

•The electrons are freed from the molecule when heated and they travel towards the cold end.

•At the cold end they collide into a molecule therefore passing all their energy to the molecule.

Comparing the 2 Mechanisms

Molecular vibration Free electron diffusion

Occurs in all solids

Slow process

Occurs in metals only

Fast process

This explains why metals heat up faster:

1. Metals have 2 mechanisms of conduction occuring at the same time.

2. In metals, free electron diffusion is the main mechanism, which is faster.

Conductors and Insulators

• Materials that can conduct heat easily and readily (eg. Metals) are known as conductors.

• Materials that do not conduct heat easily (eg. Water, air, plastic) are known as insulators.

Convection• Occurs in liquids and gases• Does not occur in solids because the molecules

are not free to move around

What happens during convection?Taking the example of heating water• Water at the bottom is heated first• Heated water expands• When water expands density decreases• Heated water of lower density starts to rise• Cooler water of higher density rushes in from sides

to take its place• The cooler water gets heated and the cycle repeats.• Convection currents are set up.• http://www.bbc.co.uk/schools/gcsebitesize/physics/energy/

energytransferrev6.shtml

Radiation• Radiation does not require a medium to

transfer heat. (can occur in a vacuum)• Sun releases electromagnetic waves

(heat is contained in the waves as infra-red)

• Hotter objects radiates more heat.

States of Matter(characteristic properties)

What state of matter does this particle motion exhibit?

SOLID!solid

retains a fixed volume and shape

not easily compressed

does not flow easily

LIQUID!liquid

assumes the shape of the part of the container retains its volume

not easily compressed

flows easily

GAS!gas

assumes the shape and volume of its container

easily compressed

flows easily

Characteristics of Solids, Liquids and Gases

gas liquid solid

takes the shape and volume of its

container

Volume remains the same, takes shape of

container

Keeps its shape and volume

easily compressed not easily compressed not easily compressed

flows easily flows easily does not flow easily

Cool Cool

States of Matter(molecular level comparison)

Particles = atoms, molecules, or ions

SOLID!solid

Ordered arrangement

rigid - particles locked into place/fixed

little free space between particles

LIQUID!liquid

disorder

particles can move/slide past one another


GAS!gas

total disorder motion: constant, rapid, random

lots of free space between particles

Collisions are elastic – total kinetic energy remains constant

Molecular Level Comparison of Solids, Liquids and Gases

solid liquid gas

Ordered arrangementdisorder

total disorder motion: constant,

rapid, random

rigid - particles locked into place/fixed

particles can move/slide past one another

lots of free space between particles



Collisions are elastic – total kinetic energy

remains constant

Cool Cool

Changes in State

Evaporation• Vaporization = the conversion of a liquid to a gas

or vapor

• Evaporation = vaporization that occurs on the surface of a liquid that is not boiling

• Only those molecules with certain minimum kinetic energy can escape from the surface of a liquid

• Evaporation rate increases when a liquid is heated…heat increases the average kinetic energy which allows particles to overcome the attractive forces that keep them in the liquid state

evaporation

CONDENSATION

Vapor/gas

LiquidGain in heat

Loss in heat

Vapor Liquid

Vapor Pressure• Vapor pressure = measure of the force

exerted by the gas above a liquid

• Constant vapor pressure = a dynamic equilibrium exists between the vapor and the liquid. The rate of evaporation = rate of condensation.

Animation of Dynamic Equilibriumhttp://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/vaporv3.swf

Boiling• Liquid in an open container

is heated• Temperature increases• Particles throughout the liquid

have enough kinetic energy to vaporize• The liquid begins to boil• Bubbles of vapor form in the liquid, rise to the

surface, and escape into the air• Boiling point = temperature at which the vapor

pressure of the liquid = external pressure on the liquid

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

Melting• Heat is applied• Particles vibrate as kinetic energy increases• Organization of the solid breaks down• The attractions that hold the particles in fixed

positions are overcome• Solid melts• Melting Point = temperature at which a solid melts

into a liquid• Freezing Point = Melting Point – they are the

same temperature and liquid and solid are in equilibrium

Liquid Solid

melting

FREEZING

Solid

Liquid

Gain in heat

Loss in heat

Sublimation• Occurs in solids with vapor pressures that

exceed atmospheric pressure at or near room temperature.

• A direct change from solid to vapor

Video of Iodine Sublimationhttp://www.youtube.com/watch?v=E-fs9OwE9Y0

Gas Solid

sublimation

deposition

Solid

Gas

Liquid

Gain in heat

Loss in heat

Phase Diagrams

Phase Diagram• A graph showing the relationships between

solid, liquid, vapor states (or phases) of a substance in a sealed container.

• Lines on the graph = conditions of pressure and temperature at which two phases exist in equilibrium

• Triple point = represents the only set of conditions in which all three phases are present in equilibrium

Homework:Interpreting Graphics 13.4 Handout

chapter 13 states of matter. kinetic energy = energy of motion kinetic theory = all matter consists...

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