3 Kinetic Theory of matter All around you objects are warming and coolingWhat causes the temperature of an object to change?Temperature is related to the motion of the particles of matter than make up an objectThe Kinetic theory of matter describes the motion of the particlesMatter is made up of atoms, molecules, or ions that are constantly in random motionParticles in motion will have kinetic energyWhen particles collide they will transfer kinetic energy from one particle to another
4 Temperature Temperature Temperature scales Measure of the average kinetic energy of its particlesAS average kinetic energy increases, temperature increasesTemperature scalesKelvin (K) SI unitCelsius (oC)Fahrenheit (oF)
5 Temperature conversions Celsius to KelvinK = oC + 273Celsius to FahrenheitoC = (5/9)(oF – 32)Fahrenheit to CelsiusoF = (9/5) oC + 32
6 Let’s PracticeWhat is -40 o F in degrees Celsius?
7 Here’s another one…What is the temperature of 22 oC in degrees Fahrenheit?
9 Thermal EnergyNot only are particles in matter constantly in motion, they are attracted to one anotherAS the particles move further apart, they gain potential energyThe sum of all the kinetic and potential energy of all the particles of an object is the thermal energy
10 HeatHeatThermal energy that flows from something at a higher temperature to something at a lower temperatureForm of energyMeasured in JoulesAlways flows from warmer materials to cooler materials
11 Specific HeatSPECIFIC HEAT OF SOME COMMON MATERIALSDifferent objects will change temperature faster than othersAs a substances is heated, temperature changes depends on:The amount of thermal energy addedNature of the substanceSpecific heat is the amount of thermal energy required to raise the temperature of 1 kg of some material by 1 oCMeasured in J/(kg oC)SubstanceSpecific Heat J/(kg oC)Water4,194Ice2,110Asphalt920Glass800Iron450
12 Changes in Thermal energy Changes in thermal energy are calculated using the following equation:Q = m x ΔT x CQ = Change in thermal energy (j)M = Mass (kg)ΔT = change in temperature (final temp – initial temp)C = specific heat of the substance
13 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?
14 Measuring specific Heat A Calorimeter is used to measure specific heatIN a Calorimeter, a heated sample transfers thermal energy to a known mass of water.The energy absorbed by the water is calculatedEnergy absorbed = energy released by the sample
16 Four states of Matter Solid Liquid Gas Plasma Tightly packed particles vibrating in spaceFixed Shape and volumeLiquidAttractive forces are weaker than in solidParticles slide past one another allowing flowDefinite volume not specific shapeGasParticles are further apartAttractive forces are very weakNO definite volume or shapePlasmaMost commonConsists of positive and negative charged particles with no definite shape or volumeResults from collisions between molecules moving at high speeds
18 Changing statesChanges in thermal energy cause substances to change from one state to anotherMeltingEnergy must be added until particles move out of their ordered arrangementEnergy required to change 1 kg of a substance from a solid to a liquid is the heat of fusionMelting point is the temperature where as solid starts to melt
19 Changing states Freezing Energy is released Particles move slower and the attraction between particles increase so that they form an ordered arrangementThe amount of energy released is also the heat of fusionFreezingheat released (negative value)MeltingHeat absorbed (positive value)
20 Changing state Vaporization Particles move faster Attractive forces weakenParticles not longer cling to each otherEvaporation occurs at the surface of the liquidEvaporation causes the surface of the liquid to decreaseHeat of vaporization is the amount of energy required for 1 kg of the liquid to become a gas at boiling point
21 Changing state Condensation Gas particles slow down Attractive forces increaseReturn to liquid stateThe amount of energy released is also the heat of vaporizationVaporizationenergy absorbed (positive value)CondensationEnergy released (negative value)
22 Heating Curve of a substance HEATING CURVE OF WATERWhen 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.
23 Thermal ExpansionSolids, liquids, and gases will expand and contract with fluctuations in temperatureSlower moving particles will be closer together smaller volumeFaster moving particles will be further apartlarger volume
25 Ways to transfer thermal energy ConductionConvectionRadiation
26 Conduction Thermal energy can be transferred when particles collide This type of energy transfer is know as conductionParticles closest to the heat source speed up, collide with nearby slow moving particles, and ultimately passing energy throughout the sampleRequired contact
27 convectionConvection is the transfer of thermal energy by movement of a fluid or gasParticles 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.
28 Radiation Radiation is the transfer of energy by electromagnetic waves Energy transferred by radiation is called radiant energyRadiation can pass through solids, liquids, and gases
29 Thermal InsulatorsThermal insulators are materials in which thermal energy moves slowlyExamples of thermal insulatorsSome plasticsWoodFiberglassAir