2 12.1 Common Temperature Scales Temperatures are reported in degreesCelsius or degrees Fahrenheit.Temperatures changed, on theother hand, are reported in Celsiusdegrees or Fahrenheit degrees:
3 12.1 Common Temperature Scales Example 1 Converting from a Fahrenheit to a Celsius TemperatureA healthy person has an oral temperature of 98.6oF. What would thisreading be on the Celsius scale?degrees above ice pointice point
4 12.1 Common Temperature Scales Example 2 Converting from a Celsius to a Fahrenheit TemperatureA time and temperature sign on a bank indicates that the outdoortemperature is -20.0oC. Find the corresponding temperature onthe Fahrenheit scale.degrees below ice pointice point
11 12.4 Linear Thermal Expansion LINEAR THERMAL EXPANSION OF A SOLIDThe length of an object changes when its temperature changes:coefficient oflinear expansionCommon Unit for the Coefficient of Linear Expansion:
13 12.4 Linear Thermal Expansion Example 3 The Buckling of a SidewalkA concrete sidewalk is constructed betweentwo buildings on a day when the temperatureis 25oC. As the temperature rises to 38oC,the slabs expand, but no space is provided forthermal expansion. Determine the distance yin part (b) of the drawing.
15 12.4 Linear Thermal Expansion Example 4 The Stress on a Steel BeamThe beam is mounted between twoconcrete supports when the temperatureis 23oC. What compressional stressmust the concrete supports apply toeach end of the beam, if they areto keep the beam from expandingwhen the temperature rises to 42oC?
19 12.4 Linear Thermal Expansion Conceptual Example 7 Expanding CylindersEach cylinder is made from a different material.All three have the same temperature and theybarely fit inside each other.As the cylinders are heated to the same,but higher, temperature, cylinder C fallsoff, while cylinder A becomes tightly wedgedto cylinder B.Which cylinder is made from which material?
20 12.5 Volume Thermal Expansion The volume of an object changes when its temperature changes:coefficient ofvolume expansionCommon Unit for the Coefficient of Volume Expansion:
21 12.5 Volume Thermal Expansion Example 8 An Automobile RadiatorA small plastic container, called the coolant reservoir, catchesthe radiator fluid that overflows when an automobile enginebecomes hot. The radiator is made ofcopper and the coolant has anexpansion coefficient of4.0x10-4 (Co)-1. If the radiatoris filled to its 15-quart capacitywhen the engine is cold (6oC),how much overflow will spill into thereservoir when the coolant reaches itsoperating temperature (92oC)?
23 12.6 Heat and Internal Energy DEFINITION OF HEATHeat is energy that flows from a higher-temperature object to a lower-temperatureobject because of a difference in temperatures.SI Unit of Heat: joule (J)
24 12.6 Heat and Internal Energy The heat that flows from hot to coldoriginates in the internal energy ofthe hot substance.It is not correct to say that a substancecontains heat.
25 12.7 Heat and Temperature Change: Specific Heat Capacity SOLIDS AND LIQUIDSHEAT SUPPLIED OR REMOVED IN CHANGING THE TEMPERATUREOF A SUBSTANCEThe heat that must be supplied or removed to change the temperature ofa substance isspecific heatcapacityCommon Unit for Specific Heat Capacity: J/(kg·Co)
26 12.7 Heat and Temperature Change: Specific Heat Capacity
27 12.7 Heat and Temperature Change: Specific Heat Capacity Example 9 A Hot JoggerIn a half-hour, a 65-kg jogger can generate 8.0x105J of heat. This heatis removed from the body by a variety of means, including the body’s owntemperature-regulating mechanisms. If the heat were not removed, howmuch would the body temperature increase?
28 12.7 Heat and Temperature Change: Specific Heat Capacity GASESThe value of the specific heat of a gas depends on whether the pressure orvolume is held constant.This distinction is not important for solids.OTHER UNITS FOR HEAT1 kcal = 4186 joules1 cal = joules
29 12.7 Heat and Temperature Change: Specific Heat Capacity CALORIMETRYIf there is no heat loss to the surroundings,the heat lost by the hotter object equals theheat gained by the cooler ones.
30 12.7 Heat and Temperature Change: Specific Heat Capacity Example 12 Measuring the Specific Heat CapacityThe calorimeter is made of 0.15 kg of aliminumand contains 0.20 kg of water. Initially, thewater and cup have the same temperatureof 18.0oC. A kg mass of unknownmaterial is heated to a temperature of97.0oC and then added to the water.After thermal equilibrium is reached, thetemperature of the water, the cup, and thematerial is 22.0oC. Ignoring the small amountof heat gained by the thermometer, findthe specific heat capacity of theunknown material.
31 12.7 Heat and Temperature Change: Specific Heat Capacity
32 12.8 Heat and Phase Change: Latent Heat THE PHASES OF MATTER
33 12.8 Heat and Phase Change: Latent Heat Conceptual Example 13 Saving EnergySuppose you are cooking spaghetti for dinner, and the instructionssay “boil pasta in water for 10 minutes.” To cook spaghetti in an openpot with the least amount of energy, should you turn up the burnerto its fullest so the water vigorously boils, or should you turn downthe burner so the water barely boils?
34 12.8 Heat and Phase Change: Latent Heat HEAT SUPPLIED OR REMOVED IN CHANGING THE PHASEOF A SUBSTANCEThe heat that must be supplied or removed to change the phaseof a mass m of a substance islatent heatSI Units of Latent Heat: J/kg
36 12.8 Heat and Phase Change: Latent Heat Example 14 Ice-cold LemonadeIce at 0oC is placed in a Styrofoam cup containing 0.32 kg of lemonadeat 27oC. The specific heat capacity of lemonade is virtually the same asthat of water. After the ice and lemonade reach an equilibriumtemperature, some ice still remains. Assume that mass of the cup isso small that it absorbs a negligible amount of heat. Determine the massof the ice that has melted.
38 12.9 Equilibrium Between Phases of Matter Only when the temperature and vapor pressure correspond to a pointon the curved line do the liquid and vapor phases coexist in equilibrium.
39 12.9 Equilibrium Between Phases of Matter Conceptual Example 16 How to Boil Water That isCooling DownShortly after the flask is removed from the burner,the boiling stops. A cork is then placed in the neckof the flask to seal it. To restart the boiling, shouldyou pour hot or cold water over the neck of theflask?
40 Air is a mixture of gases. 12.10 HumidityAir is a mixture of gases.The total pressure is the sum of the partial pressures of the componentgases.The partial pressure of water vapor depends on weather conditions. Itcan be as low as zero or as high as the vapor pressure of water at thegiven temperature.To provide an indication of how much water vapor is in the air, weatherforecasters usually give the relative humidity:
41 Example 17 Relative Humidities 12.10 HumidityExample 17 Relative HumiditiesOne day, the partial pressure of water vapor is 2.0x103 Pa. Using thevaporization curve, determine the relative humidity if the temperatureis 32oC.
Your consent to our cookies if you continue to use this website.