1. Lesson 1-5 Chemistry Problem Solving Metric and Unit Conversions
“The Chemist’s Toolkit”

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

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

4. "Real Life" Science - Inquiry
5/10/2019
Changing Measurement Units
The Factor-Label Method the most important mathematical process in chemistry!

5. The Factor-Label Process
As you know, numbers in science almost always have some measurement units: g, 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).

6. The general form of a factor-label problem is shown below
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
Quantity - Label 1
Quantity - Label 2
Answer - Label 2
Quantity - Label 1
A “Conversion Factor”
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

7. Problem #1: Convert 1000 grams to pounds.
Sample Problem
Explanation
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 454.
1000 g
1 pound
454 g
454,000 g2 / lb
2.2 pounds
454 g
1 pound
Wrong Way – Units Don’t Cancel
Correct Way – Finish with Desired Units

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

9. KEY