Chapter 10States of Matter

10.1 Kinetic Molecular Theory (KMT)

“Particles of Matter are always in motion”

States of MatterWe will discuss the KMT in terms of :

1. Gases2. Liquids3. Solids

KMT - GasesO Ideal gas- follows all of the tenets of

the KMT.O 1. Gases consist of large numbers of

atoms/molecules that are in continuous, random motion.

O 2. The combined volume of all the atoms/molecules of the gas is negligible relative to the total volume in which the gas is contained.

Gases Cont.O 3. Attractive and repulsive forces between

gas particles is negligible.O 4. Energy can be transferred between

particles during collisions, but the average kinetic energy of the particles does not change with time (assuming temperature is constant) = collisions are elastic

O 5. The average kinetic energy of the particles is proportional to the absolute temperature.O K.E. = ½ mv2

Properties of GasesO Expansion-gases occupy the volume

of the container they are enclosed in.O Fluidity- gas particles move like

liquids because there are no attractive or repulsive forces among them

O Density- gases have low densities because of the large amounts of space between the particles.

Properties of Gases Cont.

O Compressibility- Gases can be easily condensed with an increase in pressure due to the large space between the particles.

O Diffusion- the random mixing of particles due to their constant motion.

O Effusion- gas particles pass through a tiny opening.O Rate is directly proportional to the velocities

of the particles. (Smaller particles move faster and vice-versa)

Real GasesO Those that do not conform to the 5 parts

of the KMT.O When gases are held at high pressure

and low temperatures they deviate from their expected behavior.

O Noble gases conform the most to the KMT and act like ideal gases.

O The more polar the gas molecule the more it deviates from the KMT and acts like a real gas.

10.2 LiquidsO Have a definite volume and take the

shape of its containerO Particles are closer together so their

attractive forces are stronger than in gases

(think strength of intermolecular forces)O Fluid – the ability to flow and occupy

the shape of its container.

Liquids Cont.O Density – fairly high considering the

closer arrangement of the particlesO Incompressibility- because of the

close proximity to one another, the particles in a liquid can’t be pushed much closer together.

O Diffusion- liquids move easily among other liquids. Attractive forces and temperature of the particles lends to a slower diffusion rate of the liquid particles.

Liquids Cont.O Surface Tension- a force that attracts

adjacent particles on a liquids’ surface together enough to decrease the surface area.O The higher the intermolecular forces

the higher the surface tension. O Water has a fairly high surface

tension.

Liquids Cont.O Capillary Action – the attraction of

the surface of a liquid to the surface of a solid.O MeniscusO ChromatographyO Phloem tubes in plants

Liquids Cont.O Vaporization – liquid changing to a

gasO Evaporation – vaporization at the

surface of a liquid O Individual particles gain enough

kinetic energy to break the I.F. and escape as a gas.

O Freezing – liquid changing to a solidO Due to the increased intermolecular

attractions among the particles

10.3 SolidsO Highly ordered arrangement with

minimal movement among the particles

O I.F. exert stronger forces due to this proximity

O Types:O Crystalline- geometric, repeating

pattern of particlesO Amorphous- random arrangement of

particles O Glass, obsidianO “without shape”

Solids Cont.O Melting- changing a solid to a liquid by

applying heat energyO Overcome I.F. and break apart from the

crystalline structureO Supercooled liquids (amorphous solids) –

retain some liquid properties due to their lack of a uniform, organized pattern

O High DensityO Low diffusion rate

Solids Cont.O Types of Crystals (p. 340)

O 1. Ionic - NaClO 2. Covalent Network – SiO2O 3. Metallic - CuO 4. Covalent Molecular – NH3

Changes of StateO Phase – when a substance has

uniform composition and propertiesO Melting, freezing, vaporization,

condensation, sublimation, depositionO Equilibrium – when two phases occur

at the same rate. E.g., melting freezing

Changes of State Cont.O Equilibrium Vapor Pressure – the pressure

exerted by a vapor in equilibrium with its liquid at a given temp. O Proportional to the concentration of

molecules in the vapor phase.O Increases with an increase in temperatureO Volatile liquids (those that evaporate

easily) have higher V.P. because they tend to have weaker I.F. between the molecules.

O Vapor Pressure Animation

Changes of State Cont.O Boiling – change of a liquid to vapor

at the surface and within the liquid.O Boiling point – when the V.P. equals

the atmospheric pressure.O Normal B.P. of water = 100oC, (normal

atmospheric pressure of 1 atm, 760 torr, 101.3 kPa)

O B.P. Animation

Vapor Pressures of Various Substances

Identity of SubstancesO A – Diethyl etherO B – BenzeneO C - water

Phase Diagrams

O Phase Diagram Explanation

Phase Diagram for Water