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,
1 min = 60 sec
Conversion Factors:
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, they just change the UNITS.
To change the UNITS, multiply by the CONVERSION FACTOR.

5. II. 1 Unit Conversions THE UNIT CONVERSION METHOD:
We need 3 important pieces of information:
unknown amount and units
initial amount and units
conversion factor (relating the initial units to units of unknown)

6. II. 1 Unit Conversions Example 3: How many seconds are in 20 minutes?
Unknown amount:
Initial amount:
Conversion factor:
Solution
** ALWAYS include UNITS in your calculations!

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?
Unknown amount:
Initial amount:
Conversion factor:
Solution

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?
Unknown amount:
Initial amount:
Conversion factor:
Solution

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

10. II.1 Unit Conversions Example 6
a. If mL of gold has a mass of 3.86 g, what is the mass of 5.00 mL of gold?
Unknown amount:
Initial amount:
Conversion factor:
Solution

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 mL of gold has a mass of 3.86 g, what is the volume occupied by g of gold?
Unknown amount:
Initial amount:
Conversion factor:
Solution

12. II.1 Unit Conversions SUMMARY
Identify unknown 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 cancel. You want to be left with units of unknown amount!)
4. Complete the problem by multiplying and/or dividing amounts of RHS.

13. Assignment

14. II.1 Unit Conversions Multiple Unit Conversions
We can solve problems that require more than one conversion factor.
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?
ANALYZE THE PROBLEM:
Unknown amount:
Initial amount:
Conversion factors:

15. II.1 Unit Conversions Solution: we require the connection
conversion factor 1 gives the connection:
conversion factor 2 gives the connection:
Combining conversion factors 1 and 2 gives:

16. II.1 Unit Conversions Solve for unknown amount: Unknown amount =
Initial amount x Conversion factors (1 and 2)

17. Assignment