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Units of Measurements

Measurements and Calculations. Units of Measurements. Measurement. Quantitative information Need a number and a unit Represents a quantity For example: 2 meters 2 is number Meters is unit Length is quantity

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Units of Measurements

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  1. Measurements and Calculations Units of Measurements

  2. Measurement • Quantitative information • Need a number and a unit • Represents a quantity • For example: 2 meters • 2 is number • Meters is unit • Length is quantity • Units compare what is being measured to a defined measurement standard UNITS MATTER!!

  3. Measurement • Le Systeme International d’Unites : SI • System of measurement agreed on all over the world in 1960 • Contains 7 base units • Units are defined in terms of standards of measurement that are objects or natural occurrence that are of constant value or are easily reproducible • We still use some non-SI units

  4. SI Units Quantity Symbol Base Unit Abbrev. Length l meter m Mass m kilogram kg Time t second s Temp T kelvin K Amount n mole mol

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

  6. 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/m3or g/cm3) • mass per volume

  7. Density Mass (g) Volume (cm3)

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

  9. Problem-Solving Steps • List Givens and the Unknown • List Correct Formula • Math – Algebra • Compute – Conversions, etc. • 5. Answer Rounded with UNITS

  10. To the left or right? SI Prefix Conversions 1. Find the difference between the exponents of the two prefixes. 2. Move the decimal that many places.

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

  12. 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

  13. 1) 20 cm = ______________ m 2) 0.032 L = ______________ mL 3) 45 m = ______________ nm 4) 805 dm = ______________ km SI Prefix Conversions 0.2 32 45,000 0.0805

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

  15. 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.

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

  17. 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

  18. 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

  19. 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

  20. cm yd Dimensional Analysis Taft football 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

  21. 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

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