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. Heat http://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 bottom How 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 vibration Free 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: Metals have 2 mechanisms of conduction occuring at the same time. 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?

retains a fixed volume and shape SOLID! solid retains a fixed volume and shape not easily compressed does not flow easily

What state of matter does this particle motion exhibit?

assumes the shape of the part of the container retains its volume LIQUID! liquid assumes the shape of the part of the container retains its volume not easily compressed flows easily

What state of matter does this particle motion exhibit?

assumes the shape and volume of its container GAS! gas assumes the shape and volume of its container easily compressed flows easily

Characteristics of Solids, Liquids and Gases Cool Cool 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

States of Matter (molecular level comparison) Particles = atoms, molecules, or ions

What state of matter does this particle motion exhibit?

SOLID! little free space between particles solid Ordered arrangement rigid - particles locked into place/fixed little free space between particles

What state of matter does this particle motion exhibit?

LIQUID! liquid disorder particles can move/slide past one another little free space between particles

What state of matter does this particle motion exhibit?

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 Cool Cool Molecular Level Comparison of Solids, Liquids and Gases solid liquid gas Ordered arrangement disorder 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 little free space between particles little free space between particles Collisions are elastic – total kinetic energy remains constant

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

Vapor   Liquid Vapor/gas Loss in heat Gain in heat Liquid CONDENSATION evaporation Liquid Gain in heat

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 Equilibrium http://www. mhhe

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 Loss in heat melting Gain in heat Liquid Solid FREEZING melting Solid Gain 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 Sublimation http://www.youtube.com/watch?v=E-fs9OwE9Y0

Gas   Solid Gas Loss in heat sublimation Gain in heat Solid deposition Liquid sublimation Solid Gain 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