THE METRIC SYSTEM The International System of Units

THE METRIC SYSTEM The International System of Units and A Method of Problem Solving Called Dimensional Analysis Copyright Amy Brown Science Stuff

The International System of Units If everyone is to understand what your measurements mean, you must agree on the units that will be used. By international agreement, a set of units called "The International System of Units" has been defined for scientific work. This system was adopted in 1960 by the General Conference on Weights and Measures. These units are also called metric units or SI units.

SI has seven base units Quantity Unit Name Unit Abbreviation Length meter m Mass kilogram kg Time second s or sec Temperature Kelvin K Amount of Substance mol Electric Current ampere A Luminous Intensity candela cd

Advantages of Using SI SI Units make measuring and calculating easier. Measurements are always expressed as decimals rather than fractions. It is very easy to change from one unit to another since they are based on 10. It is universally understood.

SI Prefixes can be placed in front of the base units. These prefixes are used to represent quantities that are larger or smaller than the base units. These prefixes must be memorized. Prefix Unit Abbreviation Meaning giga G 1, 000, 000 mega M 1, 000 kilo k 1, 000 hecto h 100 deca da 10 1 deci d . 1 centi c . 01 milli m . 001 micro . 000001 nano n . 00001

How many meters are in each of the following? 1 Gm = ? m 1 Mm = ? m 1 km = ? m 1 hm = ? m 1 dam = ? m ? dm = 1 m ? cm = 1 m ? mm = 1 m ? nm = 1 m 1, 000, 000 m 1, 000 m 100 m 10 dm 100 cm 1, 000 mm 1, 000, 000 nm

Metric Unit of Length The meter (m) is the SI base unit of length. Prefixes are used to indicate distances longer and shorter than a meter. What name and symbol is given to each of the following units of length? a). 000001 m b). 001 m c). 01 m d). 1 m e) 10 m f) 1000 m Micrometer m Millimeter mm Centimeter cm Decimeter dm Decameter dam Kilometer km

Metric Unit of Volume: Is the space occupied by a sample of matter. The cubic meter (m 3) is the SI derived unit for measuring volume. When chemists measure the volumes of liquids and gases, they often use a non-SI unit called the liter. m. L and cm 3 The two units, _________, are interchangeable.

Metric Unit of Mass: The quantity of matter an object contains. Weight: A measure of the pull by earth's gravity. Mass and weight are often confused. Mass is not affected by gravitational pull. Your weight on the moon would be less, but your mass on the moon would be the same. kilogram (kg) The ______is the SI base unit for measuring mass.

Give the name and symbol for each of the following units: 1. A time that is 100 times as great as 1 second = 2. A length that is 1/1000 the length of 1 meter = 3. A mass that is 1000 times as great as 1 gram = 4. A mass that is 1/1, 000 the mass of 1 gram = 1. Hectosecond (hs) 2. Millimeter (mm) 3. Kilogram (kg) 4. Microgram ( g)

State the quantity that is measured by each of the following units: 1. centigram 2. millimeter 3. Kelvin 4. millisecond 1. Mass 2. Length 3. Temperature 4. Time

How large is: 1. a kilogram, compared with a gram? 2. a millimeter, compared with a meter? 3. a centimeter, compared with a meter? 4. a nanogram, compared with a gram? 1. 1000 times larger 2. 1/1000 as large 3. 1/100 as large 5. a decameter, compared with a meter? 4. 1/1, 000, 000 as large 5. 10 times larger

Dimensional Analysis I am going to show you a process called “Dimensional Analysis” that we will use to solve problems in this class all year long. We will apply this process of dimensional analysis to the conversion between the different metric units.

“Conversion factors” are numbers that are used to change from one unit to another. Conversion factors are formed from equalities that state a relationship between two units. For example: 1 kilometer = 1000 meters. When conversion factors are used properly, all units will divide out (or cancel out) EXCEPT the unit being converted to.

Solving a Problem Using Dimensional Analysis How many kilometers are equal to 250 meters? 250 m 1 kilometer 1000 meters =. 250 km When solving a problem using dimensional analysis, start with what you are given in the problem. Decide what conversion factor should be used in the next step. In the conversion factor step, place the unit on bottom that will cancel the unit in the previous step. Proceed until you are left with the unit you are looking for.

Convert. 044 km to meters. 044 km 1000 m 1 km = 44 m Convert 4. 6 mg to grams. 4. 6 mg 1 g 1000 mg =. 0046 g

Convert 696 cm 3 to m 3 696 cm 3 (1)3 m 3 =. 000696 m 3 (100)3 cm 3 How many seconds are in. 079 years? . 079 yr 365 days 1 yr 24 hr 1 day 60 min 1 hr 60 sec 1 min = 2, 491, 344 sec

Convert. 065 km to dm. 065 km 1000 m 10 dm = 650 dm 1 km 1 m The density of manganese is 7. 21 g/cm 3. What is the density in kg/m 3? 7. 21 g 1 kg cm 3 1000 g (100)3 cm 3 (1)3 m 3 = 7210 kg/m 3

Convert 0. 44 m. L/min to microliters/sec 0. 44 m. L min 1, 000 L 1 L 1000 m. L 1 L 1 min = 7. 33 L/sec 60 sec There are 7 x 106 red blood cells in 1. 0 mm 3 of blood. How many red blood cells are in one liter of blood? 7 x 106 cells (1000)3 mm 3 (1)3 m 3 1 cm 3 1000 m. L 1. 0 mm 3 = 7 x 1012 cells/L (1)3 m 3 (100)3 cm 3 1 m. L 1 L

Created by Amy Brown – Science Stuff Copyright © May 2012 Amy Brown (aka Science Stuff) All rights reserved by author. This document is for your classroom use only. This document may not be electronically distributed or posted to a web site.