432 CHAPTER 7 The Metric System Table 7.5 Common Temperatures in both °C and °F Celsius Temperature Fahrenheit Temperature 18°C − A very cold day 0°F 0°C Freezing point of water 32°F 10°C A warm winter day 50°F 20°C A mild spring day 68°F 30°C A warm summer day 86°F 37°C Body temperature 98.6°F 100°C Boiling point of water 212°F 177°C Oven temperature for baking 351°F At a temperature of 40° − the Celsius and Fahrenheit temperatures are the same. That is, 40°C 40°F. − = − Example 3 Metric Temperatures Choose the best answer. As needed, refer to the dual-scale thermometer in Fig. 7.17. a) Minneapolis, Minnesota, on New Year’s Day might have a temperature of i) 5°C. − ii) 20C. ° iii) 40C. ° b) Baltimore, Maryland, on July 4 might have a temperature of i) ° 15 C. ii) 30C. ° iii) 45C. ° c) The oven temperature for baking a cake might be i) ° 60 C. ii) 100C. ° iii) 175 C. ° Solution a) A temperature of 20 C° is possible if it is a very mild winter, but 40 C° is much too hot. The best answer for a normal winter is 5°C. − b) The best estimate is 30 C. ° A temperature of 15 C° is too chilly, and 45 C° is too hot for July 4 in Baltimore. c) A cake bakes at temperatures well above boiling, so the only reasonable answer is 175 C. ° 7 Now try Exercise 29 Convert Temperature from Celsius to Fahrenheit or from Fahrenheit to Celsius Comparing the temperatures in Table 7.5, we see that the Celsius scale has 100° from the boiling point of water to the freezing point of water and the Fahrenheit scale has 180° from the boiling point of water to the freezing point of water. Therefore, one Celsius degree represents a greater change in temperature than one Fahrenheit degree does. In fact, one Celsius degree is the same as , 180 100 or , 9 5 Fahrenheit degrees. When converting from one system to the other system, use the following formulas. From Celsius to Fahrenheit F C 9 5 32 = + From Fahrenheit to Celsius C F 5 9 ( 32) = − Did You Know? The Kelvin Room Temperature Absolute zero Freezing point of water Boiling point of water Fahrenheit Celsius Kelvin 32˚F 77˚F 212˚F ˚F -459˚F 0˚C 25˚C 100˚C ˚C -273˚C K 273 K 298 K 373 K 0 K In the metric system, the Kelvin, K, is the base unit of temperature measurement. The Kelvin is not written with a degree symbol. In thermodynamics absolute zero is the temperature at which all molecular motion ceases. Zero Kelvin (0 K) is the temperature designation of absolute zero. Except in certain sciences, the Celsius Scale is primarily used for temperature measurement in the metric system. The temperature 0 K is equivalent to 273.15 C − ° or 459.67F. − ° The formula for converting from Kelvin to degrees Celsius is C K 273.15. ° = − Kamuran A?baba/123RF
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