Unit 1: Measurement Flashcards

1
Q

Measurement

A

assignment of numbers to an object or event

quantifies

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2
Q

Three arbitrary systems of measurement

A
  • English (imperial)
  • Metric
  • SI
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3
Q

Exact Numbers

A

Count, definition, integer number

  • No uncertainty
    • 60 min/hour
    • 1000 mL/ L
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4
Q

Inexact Numbers

A
  • Measurement
  • Uncertainty from estimation
  • Tool precision limited
  • Also limit to # decimal points
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5
Q
A
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6
Q

What is Precision?

A

how closely repeated measurements of the same quantity agree with one another

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7
Q

What is Accuracy?

A

how closely a measured value agrees with the correct value

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8
Q

Accuracy vs precision

A
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9
Q

2 kinds of Error

A

Random Error

Systematic Error

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10
Q

What is Random Error?

A

Skews data from multiple measurements in a more or less uniform way around some average value.

  • Apparatus fluctuation,
  • experiment flaw
  • human error
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11
Q

What is Systematic Error?

A

causes data to be either larger or smaller than the accepted value. Can often be found and removed

  • Inaccurate calibration,
  • dust on balance pan,
  • impurities in chemicals.
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12
Q

Significant Figures

A

digits that indicate the precision of measurements

digits of a measured number that have uncertainty only in the last digit.

Sig figs – “correct” to first estimated digit

Sig figs shows degree of uncertainty – precision

Must report proper significance

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13
Q

rules for sigfigs

A
  • All nonzero numbers
    • ex: 21.389, 2.1389 (5)
  • Any zeros between nonzero numbers.
    • ex: 80.005002 (8)
  • Trailing zero’s (at the end of a number) if the number has a decimal place:
    • ex: 67.700 (5), 10,000 (1), 12,100. (5)
  • Leading zero’s insignificant (place holders)
    • ex: 0.00009802 (4)
  • Exact numbers are infinite
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14
Q

How many significant figures are in each of the following?

  1. 7.26
  2. 7.002
  3. 7.0
  4. 240
  5. 0.0720
A
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15
Q

How many significant zero’s in each of the following?

  1. 7.0063
  2. 0.0001399012
  3. 001000
  4. 100.000
  5. 0100.
A
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16
Q

Sig Figs in Addition and Subtraction

A
  • Addition/Subtraction: # of sig figs is based on fewest decimals
    • 37.68 + 108.428 + 6.71862
17
Q

Sig Figs in Multiplication and Division

A

Multiplication/Division – based on fewest sig figs

4.237 x 1.21x10-3 x 0.00273 ÷ 11.125

18
Q

Sig figs in exponents and logs

A
  • Exponents like mult:
    • (8.134x102)3
    • (8.134x102)½
  • Logs/antilogs: # decimals = sig figs in original #
    • log 4.0x105
19
Q

Report the following with the proper number of significant digits:

  1. 4.26 + 3.831
  2. 8.321 – 2.4
  3. 63.8 x 0.80
  4. 27.2 x 15.63 ÷ 1.84
A