Thermal EnergyAtomic MotionIdeal Gas EnergyInternal EnergyVibrationsEnergy TransferHeat and WorkMechanical EquivalentCalorieBurn ItThermal EnergyThermal EnergyAtomic MotionAtomic MotionThe macroscopic properties of a system are based The macroscopic properties of a system are based on the microscopic behavior of atoms.on the microscopic behavior of atoms.Macroscopic equation of state:pressure, volume, temperatureMicroscopic laws of motion:position, velocity, energyIdeal Gas EnergyIdeal Gas EnergyKinetic theory supplies the Kinetic theory supplies the energy for an ideal gas. energy for an ideal gas. •KKavav = (3/2) = (3/2)kTkTConvert this to the total Convert this to the total system energy.system energy.•UU = (3/2) = (3/2)NkTNkT•UU = (3/2) = (3/2)nRTnRTThis energy is internal to the This energy is internal to the gas.gas.Energy based on temperature and number of moleculesInternal EnergyInternal EnergyThe kinetic energy of an The kinetic energy of an ideal gas is its ideal gas is its internal internal energyenergy..•Also called Also called thermal energythermal energyInternal energy does Internal energy does notnot include energy from external include energy from external measures.measures.•Center of mass translationCenter of mass translation•Rigid body rotationRigid body rotation•Potential from external forcePotential from external forceFextvCMVibrationsVibrationsMean particle speed is not Mean particle speed is not the only source of internal the only source of internal energy.energy.Real molecules can have Real molecules can have internal motion.internal motion.•RotationRotation•VibrationVibrationThese effects add to internal These effects add to internal energy.energy.Rotation around center of massVibration at center of massEnergy TransferEnergy TransferThermal energy changes in Thermal energy changes in a system.a system.•It flows in and outIt flows in and out•Due to changes in Due to changes in macroscopic propertiesmacroscopic propertiesWhen it is due to When it is due to temperature changes it is temperature changes it is called called heatheat..Heat flowHeat and WorkHeat and WorkWork is a process that Work is a process that represents the change in the represents the change in the mechanical energy.mechanical energy.•Force acting through a Force acting through a distancedistance•Measured in joules like Measured in joules like energyenergyHeat is a process that Heat is a process that represents the change in the represents the change in the thermal energy.thermal energy.•Due to a difference in Due to a difference in temperaturetemperature•Measured in joules like Measured in joules like energyenergyMechanical EquivalentMechanical EquivalentIn the 1800’s James Joule In the 1800’s James Joule demonstrated that demonstrated that mechanical work could mechanical work could cause a change in cause a change in temperature.temperature.Heat, like work, represented Heat, like work, represented a change in energy.a change in energy.CalorieCalorieHeat was measured by a Heat was measured by a change in temperature.change in temperature.•1 calorie (cal) is the amount 1 calorie (cal) is the amount of heat needed to raise 1 g of heat needed to raise 1 g of water by 1 of water by 1 C.C.•1 kcal = 1000 cal, and is 1 kcal = 1000 cal, and is what we call a “Calorie” for what we call a “Calorie” for food.food.Calories (or kcal) are often Calories (or kcal) are often used to measure heat or used to measure heat or internal energy.internal energy.Since SI has a unit of energy Since SI has a unit of energy (J) it remains the unit for all (J) it remains the unit for all forms of energy.forms of energy.•WorkWork•Mechanical energyMechanical energy•Potential energyPotential energy•Dissipative energyDissipative energy•HeatHeat•Thermal energyThermal energy•Internal energyInternal energy1 cal = 4.186 J1 cal = 4.186 JBurn ItBurn ItYou gobble too much ice You gobble too much ice cream and decide to walk up cream and decide to walk up stairs to burn the additional stairs to burn the additional 500 Calories.500 Calories.If your mass is 60 kg, what If your mass is 60 kg, what vertical height must you vertical height must you climb?climb?Convert to joules from kcal.Convert to joules from kcal.•WW = (500 kcal)(1000 = (500 kcal)(1000 cal/kcal)(4.186 J/cal)cal/kcal)(4.186 J/cal)•WW = 2.1 x 10 = 2.1 x 1066 J. J.Work climbing is Work climbing is WW = = mghmgh..•hh = = WW / / mg = mg = (2.1 x 10(2.1 x 1066 J) / J) / (60 kg)(9.8 m/s(60 kg)(9.8 m/s22))•hh = 3600 m. = 3600 m.Real humans are inefficient Real humans are inefficient and and hh is closer to 700 m. is closer to 700
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