412 CHAPTER 7 The Metric System Write Small and Large Numbers in the Metric System When writing numbers in many countries that use the metric system, a comma is often used in place of a decimal point and a decimal point in place of a comma. For example, the number that is written 12,345.6 in the United States, might be written as 12.345,6 in other countries. In the top photo on the left, taken in Italy, a comma is used in place of a decimal point. In the middle photo on the left, taken in Hungary, a decimal point is used in place of a comma. Additionally, in some countries, when writing very large or very small numbers, groups of three digits are separated by spaces. For example, the number that is written as 123,456,789 in the United States might be written as 123 456 789 in other countries. And the number that is written 0.123456789 might be written as 0.123 456 789 in other countries. In the bottom photo on the left, taken in Europe, spaces are used in writing the number 1,000,000. In this chapter, when a number has 5 or more digits, we will use spaces to separate groups of three digits. Basic Terms in the Metric System Because the official definitions of many metric terms are quite technical, we present them informally. The meter (m) is commonly used to measure length in the metric system. One meter is a little more than a yard. A door is about 2 meters high. The kilogram (kg) is commonly used to measure mass. The difference between mass and weight is discussed in Section 7.3. One kilogram is about 2.2 pounds. A newborn baby may have a mass of about 3 kilograms. The gram (g), a unit of mass derived from the kilogram, is used to measure small amounts. A nickel has a mass of about 5 grams. The liter ( ) is commonly used to measure volume. One liter is a little more than a quart. The gas tank of a compact car may hold 50 liters of gasoline. The metric system uses the Kelvin temperature scale. However, most sciences use the Celsius scale, which is derived from the Kelvin scale. Thus, in this chapter, we will use degree Celsius (°C) to measure temperature. The freezing point of water is 0°C, and the boiling point of water is 100°C. Some temperatures are given in both Celsius and Fahrenheit below. = = = = 0°C 32°F 23°C 73.4°F 37°C 98.6°F 100°C 212°F Water freezes Comfortable room temperature Average body temperature Water boils Prefixes Used in the Metric System The metric system is based on the number 10 and therefore is a decimal system. Prefixes are used to denote a multiple or part of a basic unit. Table 7.1 summarizes the more commonly used prefixes and their meanings. In the table, where we mention “basic units” we mean metric units without prefixes, such as meter, gram, or liter. For example, from Table 7.1, we can see that kilometer hectogram 1 1000 meters, 1 = = 100 grams, dekaliter 1 10 liters, = = = decimeter centigram 1 meter, 1 gram, 1 10 1 100 and milliliter 1 liter. 1 1000 = Evgeny Malkov/123RF
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