1. SI Units and Measurement SI Units: international system of units that scientists use to measure stuff – Meter: SI unit for distance – Gram: SI unit for mass (not weight!) – Liter: SI unit for volume PrefixMilli- (m)Centi- (c) Deci - (d) Base unit: Meter (m) Liter (L) Gram (g) Deka- (da) Hecto- (h) Kilo- (k) Scientific Notation 1000 mm = 1 m 100 cm = 1 m 10 dm = 1 m 10 m = 1 dam 100 m = 1 hm 1000 m = 1 km

2. Conversion Factors Conversion Factors are fractions that relate 2 units – The top and bottom of the fraction are equivalent, but have different units – Basically, we can rewrite equations as conversion factors Example: – 100 cm = 1 m    100 cm OR 1 m__ 1 m 100 cm

3. Practice, Part 1 On a separate sheet of paper, write conversion factors for each of the following pairs of units. For each pair of units, write BOTH conversion factors (fraction and reciprocal). Include units in your fractions!! 1. Gram and milligram2. Liter and centiliter 3. Liter and dekaliter4. Meter and kilometer 5. Gram and hectogram6. Meter and centimeter 7. Liter and deciliter8. Gram and decigram 9. Gram and kilogram10. Liter and hectoliter

4. Unit Conversions Unit Conversion: We can use conversion factors to switch a measurement from one unit to another. Example: 1.5 liters = ?? milliliters

5. Step 1 First, identify what you have been given in the problem by writing the measurement with its original units. Example: 1.5 L

6. Step 2 Next, write the possible conversion factors that relate the units you have and the units you want. Example: 1 L = 1000 mL 1 L OR 1000 mL 1000 mL 1 L

7. Step 3 Choose a conversion factor by determining which units you want to keep and which units you want to cancel. The units you want to keep (for your answer) need to be on the top of your fraction The units you want to cancel (what you have) need to be on the bottom of your fraction Example: I want milliliters.  1000 mL I have liters.  1 L

8. Step 4 Multiply your original measurement by your conversion factor. Make your original measurement into a fraction by placing a 1 in the denominator Example: 1.5 L  1.5 L x 1000 mL = 1500 mL 1 1 L Notice that the units I started with (L) cancel out with the denominator of my conversion factor! I am left with just the units I want (mL).

9. Practice, Part 2 On a separate sheet of paper, complete the following unit conversions. Show all work. 1. 4.3 hL = ?? L2. 193 mm = ?? m 3. 1.75 L = ?? cL4. 89 mg = ?? g 5. 23.2 m = ?? km6. 1.8 km = ?? M 7. 84 g = ?? hg8. 3.1 m = ?? dm 9. 14 daL = ?? L10. 35 m = ?? hm