Units of Measure & Conversions

Units of Measure & Conversions Follow along in your text Chapter 1 Section 2 Pages 10 - 16

Number vs. Quantity • Quantity - number + unit UNITS MATTER!!

M V D = Derived Units • Combination of base units. • Volume (m3 or cm3) • length  length  length 1 cm3 = 1 mL 1 dm3 = 1 L • Density (kg/m3 or g/cm3) • mass per volume

Density Mass (g) Volume (cm3)

Problem-Solving Steps 1. Analyze 2. Plan 3. Compute 4. Evaluate

Density • An object has a volume of 825 cm3 and a density of 13.6 g/cm3. Find its mass. GIVEN: V = 825 cm3 D = 13.6 g/cm3 M = ? WORK: M = DV M = (13.6 g/cm3)(825cm3) M = 11,200 g

WORK: V = M D V = 25 g 0.87 g/mL Density • A liquid has a density of 0.87 g/mL. What volume is occupied by 25 g of the liquid? GIVEN: D = 0.87 g/mL V = ? M = 25 g V = 29 mL

Warm-Up: Put the following calculations into the correct significant figures. The “calculator answer” is already provided for you. • 36.75 g + 450 g + 9.750 g = 496.5 g • 29.0 m x 0.004030 m = 0.11687 m2 • 600.000 L – 14.7561 L = 585.2439 L • 219 mm3 / 17 mm2 = 12.88235294 mm • 75.0 mol + 91.00 mol + 22.000 mol = 188 mol • 100 kg – 81 kg = 19 kg • 0.0057 g/mL / 91.2 g = 0.0000625 mL • (27.0 m x 0.312 m) + (105 m x 0.190 m) = 28.374 m2

Unit Conversionsof Measurements Follow along in your text Chapter 1 Section 2 Pages 10 - 19

SI Units Quantity Symbol Base Unit Abbrev. Length l meter m Mass m kilogram kg Time t second s Temp T Kelvin K Pressure P Pascal Pa Volume V liter L Amount n mole mol

mega- kilo- k M 106 103 BASE UNIT deci- --- d 100 10-1 centi- c 10-2 milli- m 10-3 micro-  10-6 nano- n 10-9 pico- p 10-12 SI Units Prefix Symbol Factor

To the left or right? SI Prefix Conversions 1. Find the difference between the exponents of the two prefixes. 2. The “BABY WAY”: Move the decimal that many places.

kilo- mega- M k 106 103 deci- BASE UNIT d --- 100 10-1 centi- c 10-2 milli- m 10-3 micro-  10-6 nano- n 10-9 pico- p 10-12 SI Prefix Conversions Prefix Symbol Factor move left move right

Dimensional Analysis • The “Factor-Label” Method • Units, or “labels” are canceled, or “factored” out

Dimensional Analysis • Steps: 1. Identify starting & ending units. 2. Line up conversion factors so units cancel. 3. Multiply all top numbers & divide by each bottom number. 4. Check units & answer.

NUMBER = UNIT SI Prefix Conversions 0.532 532 m = _______ km NUMBER UNIT

Dimensional Analysis • Lining up conversion factors: = 1 1 in = 2.54 cm 2.54 cm 2.54 cm 1 = 1 in = 2.54 cm 1 in 1 in

qt mL  Dimensional Analysis • How many milliliters are in 1.00 quart of milk? 1000 mL 1 L 1 L 1.057 qt 1.00 qt = 946 mL

lb cm3 Dimensional Analysis • You have 1.5 pounds of gold. Find its volume in cm3 if the density of gold is 19.3 g/cm3. 1 cm3 19.3 g 1 kg 2.2 lb 1000 g 1 kg 1.5 lb = 35 cm3

in3 L Dimensional Analysis • How many liters of water would fill a container that measures 75.0 in3? 1 L 1000 cm3 (2.54 cm)3 (1 in)3 75.0 in3 = 1.23 L

cm in Dimensional Analysis Your European hairdresser wants to cut your hair 8.0 cm shorter. How many inches will he be cutting off? 8.0 cm 1 in 2.54 cm = 3.2 in

cm yd Dimensional Analysis Lake Taylor’s football team needs 550 cm for a 1st down. How many yards is this? 1 ft 12 in 1 yd 3 ft 1 in 2.54 cm 550 cm = 6.0 yd

cm pieces Dimensional Analysis A piece of wire is 1.3 m long. How many 1.5-cm pieces can be cut from this wire? 1 piece 1.5 cm 100 cm 1 m 1.3 m = 86 pieces

1) 20 cm = ______________ m 2) 0.032 L = ______________ mL 3) 45 m = ______________ nm 4) 805 dm = ______________ km SI Prefix Conversions Practice 0.2 32 45,000 0.0805

Units of Measure & Conversions