How Do We Make Measurements next tips ?

Volume is space. The volume of a liquid, solid, or gas is the space occupiedby that substance. The base unit of volume in the metric system is the liter(L). This unit is a little larger than a quart (Table 1.3). The only other commonmetric unit for volume is the milliliter (mL), which is equal to 1023 L.1 mL 0.001 L1000 mL 1 LOne milliliter is exactly equal to one cubic centimeter (cc or cm3):1 mL 1 ccThus there are 1000 cc in 1 L.C. MassMass is the quantity of matter in an object. The base unit of mass in themetric system is the gram (g). As always in the metric system, larger andsmaller units are indicated by prefixes. The ones in common use are1 kilogram (kg) 1000 g1 milligram (mg) 0.001 gThe gram is a small unit; there are 453.6 g in one pound (Table 1.3).We use a device called a balance to measure mass. Figure 1.3 shows twotypes of laboratory balances.There is a fundamental difference between mass and weight. Mass isindependent of location. The mass of a stone, for example, is the samewhether we measure it at sea level, on top of a mountain, or in the depths ofa mine. In contrast, weight is not independent of location. Weight is the ence masses (weights) on a balance, and the gravitational pull is the same onthe unknown object and on the standard masses. Because the force of gravityis essentially constant, mass is always directly proportional to weight.D. TimeTime is the one quantity for which the units are the same in all systems:English, metric, and SI. The base unit is the second (s):60 s 1 min60 min 1 hE. TemperatureMost people in the United States are familiar with the Fahrenheit scale oftemperature. The metric system uses the centigrade, or Celsius, scale. In thisscale, the boiling point of water is set at 100°C and the freezing point at 0°C.We can convert from one scale to the other by using the following formulas:°F °C 32°C (°F 32)59E X A M P L E 1.2Normal body temperature is 98.6°F. Convert this temperature to Celsius.Solution°C (98.6 32) (66.6) 37.0°CProblem 1.2Convert:(a) 64.0°C to Fahrenheit (b) 47°F to Celsius 59 59 Figure 1.4 shows the relationship between the Fahrenheit and Celsiusscales.A third temperature scale is the Kelvin (K) scale, also called theabsolute scale. The size of a Kelvin degree is the same as that of a Celsiusdegree; the only difference is the zero point. The temperature 2273°C istaken as the zero point on the Kelvin scale. This makes conversionsbetween Kelvin and Celsius very easy. To go from Celsius to Kelvin, just add273; to go from Kelvin to Celsius, subtract 273:K °C 273°C K 273Figure 1.4 also shows the relationship between the Kelvin and Celsiusscales. Note that we don’t use the degree symbol in the Kelvin scale: 100°Cequals 373 K, not 373°K. Normal boilingpoint of waterFahrenheit Celsius Kelvin100°37°0°373310273212°98.6°32°Normal bodytemperatureNormalfreezingpoint ofwaterAbsolute zero233–459° –273° 0–40° –40°Figure 1.4 Three temperaturescalesWhy was 2273°C chosen as the zero point on the Kelvin scale? The reasonis that2273°C, or 0 K, is the lowest possible temperature. Because of this,0 K is called absolute zero. Temperature reflects how fast molecules move.The more slowly they move, the colder it gets. At absolute zero, moleculesstop moving altogether. Therefore, the temperature cannot get any lower. Forsome purposes it is convenient to have a scale that begins at the lowest possibletemperature; the Kelvin scale fulfills this need. The Kelvin is the SI unit.It is very important to have a “gut feeling” about the relative sizes of theunits in the metric system. Often, while doing calculations, the only thingthat might offer a clue that you have made an error is your understandingof the sizes of the units. For example, if you are calculating the amount ofa chemical that is dissolved in water and you come up with an answer of254 kg/mL, does your answer make sense? If you have no intuitive feelingabout the size of a kilogram or a milliliter, you will not know. If you realizethat a milliliter is about the volume of a thimble and that a standard bag ofsugar might weigh 2 kg, then you will realize that there is no way to pack254 kg into a thimble of water, and you will know that you made a mistake.