1. UNIT II.1 Unit Conversions

2. II.1 UNIT CONVERSIONS You MUST learn and use the unit conversion method (not your own method!) A CONVERSION FACTOR: is a fractional expression relating or connecting two different units.

3. II.1 UNIT CONVERSIONS Example 1: There are 60 seconds in 1 minute. In statement form: The conversion factor relates 2 units (minutes to seconds).

4. II.1 UNIT CONVERSIONS Example 2: $1.44 per dozen eggs. Conversion Factors: Conversion factors do not change the VALUE of something, ever…. We simply use them to change from one unit to another!

5. II. 1 UNIT CONVERSIONS THE UNIT CONVERSION METHOD We need 3 important pieces of information: Desired amount and units ( what we want ) Initial amount and units ( what we know ) Conversion factor (relating the initial units to units of unknown)

6. II. 1 UNIT CONVERSIONS Example 3: How many seconds are in 20 minutes?

7. II.1 UNIT CONVERSIONS Example 4: If a car can go 90km in 1 h, how far can the car go in 6.5 h?

8. II.1 UNIT CONVERSIONS Example 5: If the price of gas is $1.10 per liter (l), how much will it cost to fill a 40 liter tank?

9. II.1 UNIT CONVERSIONS HOW TO PUT EVERYTHING TOGETHER The general form of a unit conversion calculation is: (wanted amount) = ( Initial amount) x (Conversion factor)

10. II.1 UNIT CONVERSIONS Example 6 a. If 0.200 mL of gold has a mass of 3.86 g, what is the mass of 5.00 mL of gold?

11. II.1 UNIT CONVERSIONS *Important: Always ask yourself “which way do I have to write the conversion factor so that my units cancel properly?” b. If 0.200 mL of gold has a mass of 3.86 g, what is the volume occupied by 100.0 g of gold?

12. II.1 UNIT CONVERSIONS SUMMARY Identify wanted/desired amount and its units (put on left side of = sign). Identify the initial amount and its units (put on right side of = sign). 3. Identify conversion factor. (Multiply initial amount by conversion factor in such a way that one of the units cancels. You want to be left with units of wanted amount!) 4. Complete the problem by multiplying and/or dividing

13. Practice Questions: Hebden, p 11 Exercise 1. a, c, e, g, i p 14. Exercise 2. b, d, f, h, j

15. II.1 UNIT CONVERSIONS Multiple Unit Conversions We can solve problems that require more than one conversion factor. o Example: If eggs are $1.44 per dozen, and if there are 12 eggs in a dozen, how many individual eggs can be bought for $4.32?

16. II. 1 UNIT CONVERSIONS EX: The automobile gas tank of a Canadian tourist holds 39.5 l of gas. If 1 L of gas is equal to 0.264 gal in the USA (“gal” is the symbol for “gallon”, a measure of volume used in the US), and gas is $1.26/gal in Dallas, Texas, how much will it cost the tourist to fill his gas tank in Dallas?

17. Hebden, p 15 Exercises 3 - 10