Measurement of Temperature and Its Units

Early humans relied on the sense of touch or vision to measure how cold or how warm something was. In fact, we still rely on touch tod. When you are plannii to take a bath, you first turn the hot and cold water on and let the bathmb fill with water. Before you enter the tub, however, you first touch the water to fedl how warm it is. Basically, you are using your sense of touch to get an indicadon of the temperature. Of course, using toudi alone, you can t quantify the temperature of water accurately. You cannot say, for example, that the v ter is at 21.5 C. 

So note the need for a more precise way of quantifying what the temperature of something is. Moreover, when we express the temperature of water, we need to use a number that is understood by all. In other words, we need to establish and use the same units and scales that are understood by ever3mne. 

Another example of how people relied on their senses to quantify temperature is the way blacksmiths used to use their eyes to estimate how hot a fire was. They judged the temperature by the color of the burning fuel before they placed the horseshoe or an iron piece in the fire. In fact, this relationship between the color of heated iron and its actual temperature has been measured and established. Table 11.1 shows this relationship. 

From these examples, you see that our senses are usefiil in jud ng how cold or how hot something is, but they are limited in accuracy and cannot quantify a value for a temperature. Thus, we need a measuring device that can provide information about the temperature of something more accurately and effectively. 

As with other instruments, thermometers evolved over time into today s accurate instruments that can measure temperature to 1/100°C increments. 

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