Lesson 1-2 Scientific Measuring Metric and Unit Conversions “The Scientist’s Toolkit”

What is unique about Problem Solving In Science? 1.Metrics –System accepted by most of the world –Simple – Units are multiples of 10 2.Use the Factor – Label Method also called “dimensional analysis” or the “railroad track” method –A procedure for keeping track of and converting units

Changing Metric Units grams meters liters To most easily change from one prefix to another in the metric system you move the decimal.

The Factor-Label Method the most important mathematical process in chemistry! Changing Measurement Units

The Factor-Label Process As you know, numbers in science almost always have some measurement units: 300 g, 0.62 Km, 0°C The numbers are factors, and units are labels: 300 is a factor and grams is the label 0.62 is a factor and Kilometer is the label 0 is a factor and degrees Celsius is the label With the factor-label process we consider both the “factor” and the “label” when we calculate answers. The factors and labels are equally important - they are a team - and when multiplying a factor (number), we must also consider the label (units).

A “Conversion Factor” Quantity - Label 1Quantity - Label 2Answer - Label 2 Quantity - Label 1 The general form of a factor-label problem is shown below. The factor-label method is a tool that allows us to write down the calculations that are in our brain, and to keep track of the relationship between quantities with different “labels”. The critical step in the factor-label method is using conversion factors When we use factor label it’s important to understand that each space in the chart represents a multiplication or a division when using our calculator

Problem #1: Convert 1000 grams to pounds. Sample ProblemExplanation Write what is given. Draw the horizontal and vertical lines. It is known that 454 grams = 1 pound. This becomes our conversion factor. The problem is solved when the label of “pounds” is in the numerator and all other units are canceled. The fraction is turned to put grams on bottom so it will cancel the “grams” labels. Use your calculator to do the math times 1 divide by g1 pound 454 g 1 pound 2.2 pounds 454,000 g 2 / lb Wrong Way – Units Don’t Cancel Correct Way – Finish with Desired Units

Problem #2: Convert 65 miles/hour to meters/second.

KEY 1)Convert milliliters to dekaliters mL = daL 2)Convert hectograms to milligrams hg = 60 mg 3) 4)

5) 6)