Percent Error

1
Percent Error

• Error 100 measured - accepted
• accepted

2
Error for each student?

• Std. Density of sucrose 1.59 g/cm3
• A 1.57 g/cm3
• B 1.51 g/cm3
• C 1.70 g/cm3

3

• Significant digits are used only for measured
  quantities.

4

• Exact numbers definitions do NOT affect the
  number of significant digits in answer because
  exact numbers are not measurements.

5
Sig. Digit Calculations

• Multiplication / division The number with the
  least number of significant digits determines the
  number of significant digits in the answer.

6
Sig. Digit Calculations

• Addn. / subtraction Find the last sig. digit of
  each number. The one in the left-most column is
  the column of the last significant digit in the
  answer.

7
Sig. Digit Calculations

• Rounding
• If first digit to be eliminated is greater than
  or equal to 5 (.1), round up.

8
Calculate the following

• 0.3287 m 45.2 m ?

9
Calculate the following

• 1250g - 234.207g ?
• 52.69

10
Calculate the following

• 125.5 kg 52.68 kg 2.1 kg

11

• (52.8 Pa 3.0025 Pa)
• 253.4 Pa ?

12

• (78.26 L - 89.50 L)
• (678.2 L 9511 L) ?

13
Measuring

• Record ALL the digits you can read.
• Estimate an additional digit.
• Last digit on a digital display is estimated.

14
Uncertainty

• is a range that the actual value falls within.
• Example 10.0 g 0.2 g means that the mass is
  between 9.8 and 10.2 g.

15
How do you write this answer?

• 2340 g 4660 g ?

16
Review 1

• Dimensional Analysis is used for?

7.00 x 103 g
17
Review 1

• Dimensional Analysis is used for making
  conversions or with problems of mixed units.

18
Review 2

• Accuracy?
• Precision?

19
Review 2

• Accuracy how close the measurement is to the
  standard.
• Precision how close measurements are to each
  other.

20
Review 3

• How to take a correct measurement?

21
Review 3

• How to take a correct measurement? Use all
  marked digits plus one estimated digit

22
Review 4

• Error?

23
Review 4

• Error 100 measured - accepted
• accepted

24
Review 5

• of significant figures when adding or subtrct.
  measurements?

25
Review 5

• of significant figures when adding or subtrct.
  measurements?Last digit in leftmost column is
  last column of answer

26
Review 6

• of significant figures when multiplying or
  dividing measurements?

27
Review 6

• of significant figures when multiplying or
  dividing measurements?The least digits in any
  of the measurements