chap06 - Learning Services Home

Measuring TemperatureSome people might say that the water in a swimming pool feelswarm, although others might say it feels cool. Because the temperatureof the water feels different to different people, you cannotdescribe or measure temperature accurately by how it feels.Remember that temperature is related to the kinetic energy of allthe atoms in an object. You might think that to measure temperature,you must measure the kinetic energy of the atoms. But atomsare so small that even a tiny piece of material consists of trillionsand trillions of atoms. Because they are so small and objects containso many of them, it is impossible to measure the kinetic energyof all the individual atoms. However, a practical way to measuretemperature is to use a thermometer, as shown in Figure 13.Why can’t the kinetic energy of all the atoms inan object be measured?Figure 13 This thermometeruses the height of a liquid in a tubeto measure temperature. The liquidheight changes with temperaturebecause the liquid expands asits temperature increases. Thethermometer is calibrated bymarking the liquid height at twoknown temperatures.The Fahrenheit Scale One temperature scale you might befamiliar with is the Fahrenheit (FAYR un hite) scale. On theFahrenheit scale, the freezing point of water is given the temperature32°F, and the boiling point is 212°F. The space between theboiling point and the freezing point is divided into 180 equaldegrees. The Fahrenheit scale currently is used mainly in theUnited States.BeakerGlass tubeMark heightof liquidBoiling point100°CIce cubeMark heightof liquidBoilingwaterOne hundredequal divisionsLiquidFreezing point0°CThe height of the liquid is markedwhen the thermometer is placed inwater at 0°C.The height of the liquid is markedwhen the thermometer is placedin boiling water at 100°C.Make a temperature scaleby dividing the distancebetween the two marksinto equal degrees.172 CHAPTER 6 Energy