HEAT AND STATES OF MATTER CHAPTER 9
Dec 29, 2015
HEAT AND STATES OF MATTER
CHAPTER 9
TEMPERATURE AND THERMAL ENERGYSECTION 1
KINETIC THEORY OF MATTER
• ALL AROUND YOU OBJECTS ARE WARMING AND COOLING
• WHAT CAUSES THE TEMPERATURE OF AN OBJECT TO CHANGE?
• TEMPERATURE IS RELATED TO THE MOTION OF THE PARTICLES OF MATTER THAN MAKE UP AN OBJECT
• THE KINETIC THEORY OF MATTER DESCRIBES THE MOTION OF THE PARTICLES
• MATTER IS MADE UP OF ATOMS, MOLECULES, OR IONS THAT ARE CONSTANTLY IN RANDOM MOTION
• PARTICLES IN MOTION WILL HAVE KINETIC ENERGY
• WHEN PARTICLES COLLIDE THEY WILL TRANSFER KINETIC ENERGY FROM ONE PARTICLE TO ANOTHER
TEMPERATURE
• TEMPERATURE
• MEASURE OF THE AVERAGE KINETIC ENERGY OF ITS PARTICLES
• AS AVERAGE KINETIC ENERGY INCREASES, TEMPERATURE INCREASES
• TEMPERATURE SCALES
• KELVIN (K) SI UNIT
• CELSIUS (OC)
• FAHRENHEIT (OF)
TEMPERATURE CONVERSIONS
• CELSIUS TO KELVIN
• K = OC + 273
• CELSIUS TO FAHRENHEIT
• OC = (5/9)(OF – 32)
• FAHRENHEIT TO CELSIUS
• OF = (9/5) OC + 32
LET’S PRACTICE
• WHAT IS -40 O F IN DEGREES CELSIUS?
HERE’S ANOTHER ONE…
• WHAT IS THE TEMPERATURE OF 22 OC IN DEGREES FAHRENHEIT?
ONE MORE…
• WHAT IS 25 OC IN KELVIN?
THERMAL ENERGY
• NOT ONLY ARE PARTICLES IN MATTER CONSTANTLY IN MOTION, THEY ARE ATTRACTED TO ONE ANOTHER
• AS THE PARTICLES MOVE FURTHER APART, THEY GAIN POTENTIAL ENERGY
• THE SUM OF ALL THE KINETIC AND POTENTIAL ENERGY OF ALL THE PARTICLES OF AN OBJECT IS THE THERMAL ENERGY
HEAT
• HEAT
• THERMAL ENERGY THAT FLOWS FROM SOMETHING AT A HIGHER TEMPERATURE TO SOMETHING AT A LOWER TEMPERATURE
• FORM OF ENERGY
• MEASURED IN JOULES
• ALWAYS FLOWS FROM WARMER MATERIALS TO COOLER MATERIALS
SPECIFIC HEAT
• DIFFERENT OBJECTS WILL CHANGE TEMPERATURE FASTER THAN OTHERS
• AS A SUBSTANCES IS HEATED, TEMPERATURE CHANGES DEPENDS ON:
• THE AMOUNT OF THERMAL ENERGY ADDED
• NATURE OF THE SUBSTANCE
• SPECIFIC HEAT IS THE AMOUNT OF THERMAL ENERGY REQUIRED TO RAISE THE TEMPERATURE OF 1 KG OF SOME MATERIAL BY 1 OC
• MEASURED IN J/(KG OC)
Substance Specific Heat J/(kg oC)
Water 4,194
Ice 2,110
Asphalt 920
Glass 800
Iron 450
SPECIFIC HEAT OF SOME COMMON MATERIALS
CHANGES IN THERMAL ENERGY
• CHANGES IN THERMAL ENERGY ARE CALCULATED USING THE FOLLOWING EQUATION:
• Q = M X ΔT X C
• Q = CHANGE IN THERMAL ENERGY (J)
• M = MASS (KG)
• ΔT = CHANGE IN TEMPERATURE (FINAL TEMP – INITIAL TEMP)
• C = SPECIFIC HEAT OF THE SUBSTANCE
LET’S TRY IT…
• THE AIR IN A LIVING ROOM HAS A MASS OF 72 KG AN. D A SPECIFIC HEAT OF 1,010 J/(KGOC). WHAT IS THE CHANGE IN THERMAL ENERGY OF THE AIR WHEN IT WARMS FROM 20OC TO 25OC?
MEASURING SPECIFIC HEAT
• A CALORIMETER IS USED TO MEASURE SPECIFIC HEAT
• IN A CALORIMETER, A HEATED SAMPLE TRANSFERS THERMAL ENERGY TO A KNOWN MASS OF WATER.
• THE ENERGY ABSORBED BY THE WATER IS CALCULATED
• ENERGY ABSORBED = ENERGY RELEASED BY THE SAMPLE
STATES OF MATTERSECTION 2
FOUR STATES OF MATTER
• SOLID
• TIGHTLY PACKED PARTICLES VIBRATING IN SPACE
• FIXED SHAPE AND VOLUME
• LIQUID
• ATTRACTIVE FORCES ARE WEAKER THAN IN SOLID
• PARTICLES SLIDE PAST ONE ANOTHER ALLOWING FLOW
• DEFINITE VOLUME NOT SPECIFIC SHAPE
• GAS
• PARTICLES ARE FURTHER APART
• ATTRACTIVE FORCES ARE VERY WEAK
• NO DEFINITE VOLUME OR SHAPE
• PLASMA
• MOST COMMON
• CONSISTS OF POSITIVE AND NEGATIVE CHARGED PARTICLES WITH NO DEFINITE SHAPE OR VOLUME
• RESULTS FROM COLLISIONS BETWEEN MOLECULES MOVING AT HIGH SPEEDS
STATES OF MATTER
CHANGING STATES
• CHANGES IN THERMAL ENERGY CAUSE SUBSTANCES TO CHANGE FROM ONE STATE TO ANOTHER
• MELTING
• ENERGY MUST BE ADDED UNTIL PARTICLES MOVE OUT OF THEIR ORDERED ARRANGEMENT
• ENERGY REQUIRED TO CHANGE 1 KG OF A SUBSTANCE FROM A SOLID TO A LIQUID IS THE HEAT OF FUSION
• MELTING POINT IS THE TEMPERATURE WHERE AS SOLID STARTS TO MELT
CHANGING STATES
• FREEZING
• ENERGY IS RELEASED
• PARTICLES MOVE SLOWER AND THE ATTRACTION BETWEEN PARTICLES INCREASE SO THAT THEY FORM AN ORDERED ARRANGEMENT
• THE AMOUNT OF ENERGY RELEASED IS ALSO THE HEAT OF FUSION
• FREEZINGHEAT RELEASED (NEGATIVE VALUE)
• MELTINGHEAT ABSORBED (POSITIVE VALUE)
CHANGING STATE
• VAPORIZATION
• PARTICLES MOVE FASTER
• ATTRACTIVE FORCES WEAKEN
• PARTICLES NOT LONGER CLING TO EACH OTHER
• EVAPORATION OCCURS AT THE SURFACE OF THE LIQUID
• EVAPORATION CAUSES THE SURFACE OF THE LIQUID TO DECREASE
• HEAT OF VAPORIZATION IS THE AMOUNT OF ENERGY REQUIRED FOR 1 KG OF THE LIQUID TO BECOME A GAS AT BOILING POINT
CHANGING STATE
• CONDENSATION
• GAS PARTICLES SLOW DOWN
• ATTRACTIVE FORCES INCREASE
• RETURN TO LIQUID STATE
• THE AMOUNT OF ENERGY RELEASED IS ALSO THE HEAT OF VAPORIZATION
• VAPORIZATIONENERGY ABSORBED (POSITIVE VALUE)
• CONDENSATIONENERGY RELEASED (NEGATIVE VALUE)
HEATING CURVE OF A SUBSTANCE
• WHEN THE SYSTEM IS HEATED, ENERGY IS TRANSFERRED INTO IT.
• IN RESPONSE TO THE ENERGY IT RECEIVES, THE SYSTEM CHANGES, FOR EXAMPLE BY INCREASING ITS TEMPERATURE.
• A PLOT OF THE TEMPERATURE VERSUS TIME IS CALLED THE HEATING CURVE.
HEATING CURVE OF WATER
THERMAL EXPANSION
• SOLIDS, LIQUIDS, AND GASES WILL EXPAND AND CONTRACT WITH FLUCTUATIONS IN TEMPERATURE
• SLOWER MOVING PARTICLES WILL BE CLOSER TOGETHER SMALLER VOLUME
• FASTER MOVING PARTICLES WILL BE FURTHER APARTLARGER VOLUME
TRANSFERRING THERMAL ENERGYSECTION 3
WAYS TO TRANSFER THERMAL ENERGY
• CONDUCTION
• CONVECTION
• RADIATION
CONDUCTION
• THERMAL ENERGY CAN BE TRANSFERRED WHEN PARTICLES COLLIDE
• THIS TYPE OF ENERGY TRANSFER IS KNOW AS CONDUCTION
• PARTICLES CLOSEST TO THE HEAT SOURCE SPEED UP, COLLIDE WITH NEARBY SLOW MOVING PARTICLES, AND ULTIMATELY PASSING ENERGY THROUGHOUT THE SAMPLE
• REQUIRED CONTACT
CONVECTION
• CONVECTION IS THE TRANSFER OF THERMAL ENERGY BY MOVEMENT OF A FLUID OR GAS
• PARTICLES GAIN ENERGY FROM HEAT SOURCE.
• WARM AIR IS LESS DENSE AND WILL RISE.
• AS WARM AIR IS RISING, COOL AIR FROM THE SIDE REPLACES HEATED AIR CAUSING A CIRCULAR CONVECTION CURRENT.
RADIATION
• RADIATION IS THE TRANSFER OF ENERGY BY ELECTROMAGNETIC WAVES
• ENERGY TRANSFERRED BY RADIATION IS CALLED RADIANT ENERGY
• RADIATION CAN PASS THROUGH SOLIDS, LIQUIDS, AND GASES
THERMAL INSULATORS
• THERMAL INSULATORS ARE MATERIALS IN WHICH THERMAL ENERGY MOVES SLOWLY
• EXAMPLES OF THERMAL INSULATORS
• SOME PLASTICS
• WOOD
• FIBERGLASS
• AIR