Unit 1: Measurement

Question 1

Measurement

Answer 1

assignment of numbers to an object or event

quantifies

Question 2

Three arbitrary systems of measurement

Answer 2

• English (imperial)
• Metric
• SI

Question 3

Exact Numbers

Answer 3

Count, definition, integer number

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

Question 4

Inexact Numbers

Answer 4

• Measurement
• Uncertainty from estimation
• Tool precision limited
• Also limit to # decimal points

Question 5

Question 6

What is Precision?

Answer 6

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

Question 7

What is Accuracy?

Answer 7

how closely a measured value agrees with the correct value

Question 8

Accuracy vs precision

Answer 8

Question 9

2 kinds of Error

Answer 9

Random Error

Systematic Error

Question 10

What is Random Error?

Answer 10

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

• Apparatus fluctuation,
• experiment flaw
• human error

Question 11

What is Systematic Error?

Answer 11

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.

Question 12

Significant Figures

Answer 12

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

Question 13

rules for sigfigs

Answer 13

• 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

Question 14

How many significant figures are in each of the following?

1. 7.26
2. 7.002
3. 7.0
4. 240
5. 0.0720

Question 15

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

1. 7.0063
2. 0.0001399012
3. 001000
4. 100.000
5. 0100.

Question 16

Sig Figs in Addition and Subtraction

Answer 16

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

Question 17

Sig Figs in Multiplication and Division

Answer 17

Multiplication/Division – based on fewest sig figs

4.237 x 1.21x10-3 x 0.00273 ÷ 11.125

Question 18

Sig figs in exponents and logs

Answer 18

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

Question 19

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