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iii. Measurement

iii. Measurement. Units of Measurement SI Base Units & Prefixes Derived Units Calculations Significant Figures Precision and Accuracy. B. SI Units. Quantity. Base Unit. Symbol. Length. _______. m. Mass. kilogram. ____. Time. _______. s. Temp. kelvin. ____. Current.

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iii. Measurement

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  1. iii. Measurement Units of Measurement SI Base Units & Prefixes Derived Units Calculations Significant Figures Precision and Accuracy

  2. B. SI Units Quantity Base Unit Symbol Length _______ m Mass kilogram ____ Time _______ s Temp kelvin ____ Current _______ A

  3. Metric Conversions • 6000 liters = ________ kl • 0.23 g = _________mg • 5 hm= ________ cm • 9 g = ______ dg

  4. Density • Density – an object’s mass per unit volume • A physical property • Formula: • D = M/V • M – mass (g) • V – volume (mL) or (cm3)

  5. M 6g D D V 3ml Triangle Method Put the formula in the triangle. Solve for the unknown. EXAMPLE: A 6 gram object has a volume of 3 ml. What is its density? Density = mass/volume so,

  6. M D = D V C. Derived Units • Combination of base units. • Volume - length  _____  _______ 1 cm3 = 1 ____ • Density - mass per unit ______ (g/cm3)

  7. M D V D. 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 = 11,220 g

  8. WORK: V = M D V = 25 g 0.87 g/mL M D V D. Density 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 V = 28.7 mL

  9. WORK: D = M V D = 620 g 753 cm3 M D V D. Density 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 = ? D = 0.82 g/cm3

  10. Your turn to try! • The density of an object is 2.6 g/ml. It has a mass of 9 grams. Give its volume. • A cube is 3 cm long, 3 cm wide, and 3 cm tall. It has a mass of 7 grams. What is its density? • The density of an object is 0.98 g/ml. It has a volume of 19 cubic cm. What is its mass?

  11. Significant Figures • Learn these rules: • All nonzero digits are significant. 876 • Zeros to right of decimal and to right of non zero digit are significant. 692.00 • Zeros between 2 nonzero digits are significant. 90,909 90,087.00101 • Zeros to the left of a decimal and left of a nonzero digit are not significant. 0.0210 • Zeros to the right of a decimal that serve as placeholders before nonzero digits are not significant. 0.0000003109901 • Zeros to the left of an understood decimal and to the right of nonzero digits are not significant. 9,340,010,000

  12. How many SF are in each? • 3,000.21 • 45.9009 • 9,090,000 • 821.000340 • 124,678 • 0.001201340 • 99.100 • 0. 90101

  13. Operations Using SFs • When adding or subtracting, the answer should contain the same number of decimal places as the number with the least number decimal places in the problem. Ex. 500.1 + 11.22 = 511.32 = 511.3 1 DP 2 DP 2DP 1DP Ex. 455.564 - 50.1 = 405.464 = 405.5 3DP 1DP 3DP 1DP

  14. Operations Using SFs • When multiplying or dividing, the answer should contain the same number of SF as the number with the least number SF in the problem. Ex. 500 x 11 = 5,500 = 6000 1 SF 2 SF 2SF 1SF Ex. 45/9.0 = 5 = 5.0 both have 2 SFs

  15. Try these • Answer the following in proper number of SFs. • 34.2 x 13 = • 9 x 2 = • 95.0/9 = • 1/4 = • 32/4.0=

  16. Precision vs. Accuracy • Precision is the ________ of a measurement to other measurements made in the same way. • Accuracy is the ________ of a measurement to the accepted value.

  17. Accuracy and Precision Ex. You throw 3 darts. All three hit in the outer edge of the board within a few cm of each other. You are _______ with the throw but not ________. Ex. You throw 3 darts. All 3 hit in the center of the bulls eye. You throws were very _________ and they also were _________.

  18. Another example • You use a balance to get the mass of an object. You do it three times. You get the answers 2 g, 9 g, and 10 grams. Your average is 7 grams. The book value is also 7 grams. • Were you precise? • Were you accurate?

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