Chapter 10: States of Matter

CHAPTER 10: STATES OF MATTER

KINETIC MOLECULAR THEORY

•GASES ARE COMPOSED OF PARTICLES WITH NO ATTRACTIVE FORCES BETWEEN THEM.

•GAS PARTICLES ARE ALWAYS IN MOTION.

•PARTICLES TRAVEL IN A STRAIGHT PATH.

•PARTICLES CHANGE DIRECTION ONLY WHEN THEY REBOUND FROM A COLLISION.

•THE KINETIC ENERGY (SPEED) OF THESE PARTICLES INCREASES AS THE TEMPERATURE INCREASES.

•ALL COLLISIONS ARE ELASTIC.

•TOTAL KINETIC ENERGY OF THE SYSTEM REMAINS CONSTANT.

•TEMPERATURE & KINETIC ENERGY ARE DIRECTLY PROPORTIONAL.

STATES OF MATTER

•INTERMOLECULER FORCES:

ATTRACTIVE FORCES BETWEEN MOLECULES

•SOLIDS

•VERY LOW KE

•PARTICLES CAN’T MOVE

•FIXED SHAPE & VOLUME

•STRONG INTERMOLECULAR FORCES

•THERE ARE TWO TYPES OF SOLIDS

1. IONIC SOLIDS

2. MOLECULAR SOLIDS

•IONIC SOLID: COMPOSED OF IONS (METAL + NONMETAL)

•MOLECULAR SOLID:COMPOSED OF MOLECULES (NONMETALS)

STATES OF MATTER

•MELTING POINT:TEMPERTURE A SOLID TURNS INTO A LIQUID

- MELTING PT = FREEZING PT

•IONIC SOLIDS: HAVE A HIGH MP

•MOLECULAR SOLIDS: HAVE A LOW MP

•MOST SOLIDS HAVE A CRYSTAL STRUCTURE.

•CRYSTAL: THE ATOMS ARE ARRANGED IN AN ORDERLY,REPEATING 3D PATTERN (CRYSTAL LATTICE)

•UNIT CELL: THE SMALLEST GROUP OF PARTICLES WITH IN A CRYSTAL WHICH HAVE THE PROPERTIES OF THE CRYSTAL

STATES OF MATTER

STATES OF MATTER

•AMORPHOUS SOLIDS: LACK AN INTERNAL CRYSTAL STRUCTURE. THEY HAVE NO SHAPE.

•ALLOTROPES: DIFFERENT FORMS OF THE SAME ELEMENT. (ARRANGEMENT DIFFERS)

•CARBON HAS FOUR DIFFERENT FORMS.

•LIQUIDS

•LOW KE

•PARTICLES CAN MOVE A LITTLE

•VARIABLE SHAPE

•FIXED VOLUME

•INCREASE IN PRESSURE HAS NO EFFECT ON VOLUME.

•CONDENSED STATE OF MATTER

•TWO SPECIAL PROPERTIES EXIST IN A LIQUID:

1. SURFACE TENSION

2. CAPILLARY ACTION

•SURFACE TENSION: ATTRACTIVE FORCES BETWEEN PARTICLES IN A LIQUID THAT MINIMIZE SURFACE AREA.

•CAPILLARY ACTION: ATTRACTIVE FORCE BETWEEN THE SURFACE OF A LIQUID & THE SURFACE OF A SOLID.

•GASES

•HIGH KE

•PARTICLES MOVE INDEPENDENTLY

•VARIABLE SHAPE

•VARIABLE VOLUME

•PARTICLES CREATE PRESSURE WHEN THEY COLLIDE WITH OTHER PARTICLES.

•GAS PRESSURE: THE FORCE EXERTED BY A GAS PER UNIT SURFACE AREA OF AN OBJECT.

•ATMOSPHERIC PRESSURE: RESULTS FROM THE COLLISIONS OF AIR MOLECULES WITH OBJECTS.

•BAROMETER: A DEVICE USED TO MEASURE ATMOSPHERIC PRESSURE. IT DEPENDS ON THE WEATHER.

•STANDARD PRESSURE (atm): THE PRESSURE REQUIRED TO SUPPORT 760 mm Hg IN A MERCURY BAROMETER.

•THE SI UNIT OF PRESSURE IS THE PASCAL (Pa).

•UNITS FOR PRESSURE

•1 atm

•760 mmHg

•101.325 kPa

•101325 Pa

•760 Torr

•ALL UNITS ARE EQUIVALENT TO EACH OTHER.

•EXAMPLES:

PHASE CHANGES

•VAPORIZATION: THE CHANGE FROM A LIQUID TO A GAS BELOW ITS BOILING POINT.

•EVAPORATION: -VAPORIZATION OF AN UNCONTAINED LIQUID

-MOLECULES WITH ENOUGH KE AT THE SURFACE ESCAPE TO BECOME A GAS

•CONDENSATION:THE CHANGE FROM A GAS TO A LIQUID

•EQUILIBRIUM: TRAPPED MOLECULES REACH A BALANCE BETWEEN EVAPORATION & CONDENSATION.

•SUBLIMATION:THE CHANGE FROM A SOLID TO A GAS.

•VAPOR PRESSURE:PRESSURE OF VAPOR ABOVE A LIQUID AT EQUILIBRIUM

-DEPENDS ON TEMPERATURE & INTERMOLECULAR FORCES

•BOILING POINT:TEMPERATURE AT WHICH VAPOR PRESSURE OF A LIQUID EQUALS EXTERNAL PRESSURE

•NORMAL BOILING POINT:TEMPERATURE A SUBSTANCE BOILS AT 1 atm.

•TEMPERATURE & PRESSURE HAVE A DIRECT RELATIONSHIP.

•PHASE DIAGRAMS: A GRAPHICAL WAY TO DEPICT THE EFFECTS OF PRESSURE & TEMPERATURE ON THE PHASE OF A SUBSTANCE.

•THE CURVES INDICATE THE CONDITIONS OF T & P UNDER WHICH EQUILIBRIUM BETWEEN DIFFERENT PHASES OF A SUBSTANCE CAN EXIST.

•VAPOR PRESSURE CURVE:THE BORDER BETWEEN THE LIQUID & GASSTATE OF THE SUBSTANCE.

•CRITICAL POINT:THE TEMPERATURE ABOVE WHICH THE GAS CANNOT BE LIQUEFIED NO MATTER HOW MUCH PRESSURE IS APPLIED.

•TRIPLE POINT:THE PARTICULAR CONDITION OF TEMPERATURE & PRESSURE WHERE ALL THREE STATES ARE IN EQUILIBRIUM