 Ch. 2 - Measurement I. Units of Measurement (p.34-45)

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Ch. 2 - Measurement I. Units of Measurement (p.34-45)
Number vs. Quantity SI Base Units & Prefixes Derived Units Density Calculations

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

B. SI Units Base Unit Length- I meter m Mass- m gram g Time- t second
Quantity & Symbol Base Unit Unit Symbol Length- I meter m Mass- m gram g Time- t second s Temp- T kelvin K Current- I ampere A

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

D m V D= m V C. Derived Units Combination of base units.
Volume - length  length  length 1 cm3 = 1 mL dm3 = 1 L Density - mass per unit volume (g/cm3) D m V D= m V

Problem Solving Steps 1 Givens: 2 Unknowns: 3 Equations: 4 Answer:

D m V D. Density V = 825 cm3 m = DV D = 13.6 g/cm3
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 = 11,220 g D m V

Problem Solving Steps 1 Givens:
Include quantity, number, & unit symbols 2 Unknowns: Include quantity & unit symbols 3 Equations: Base equation & manipulated equation 4 Answer: Do the units agree? Is it reasonable?

D m V D. Density D = 0.87 g/mL V = m V = ? m = 25 g V = 25 g 0.87 g/mL
1) 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 WORK: V = m D D m V V = g 0.87 g/mL V = 28.7 mL

D m V D. Density m = 620 g D = m V = 753 cm3 D = ? D = 620 g 753 cm3
2) You have a sample with a mass of 620 g & a volume of 753 cm3. Find density. GIVEN: m = 620 g V = 753 cm3 D = ? WORK: D = m V D m V D = g 753 cm3 D = 0.82 g/cm3