1. Accuracy and Precision
Section 3 Using Scientific Measurements
Chapter 2
Accuracy and Precision
Accuracy - closeness of measurements to the correct or accepted value of the quantity measured.
Precision - closeness of a set of measurements of the same quantity made in the same way.

2. Accuracy and Precision
Section 3 Using Scientific Measurements
Chapter 2
Accuracy and Precision

3. Section 3 Using Scientific Measurements
Chapter 2
Percentage error – percentage a measurement is off from the accepted value

4. Chapter 2 Sample Problem C
Section 3 Using Scientific Measurements
Chapter 2
Sample Problem C
A student measures the mass and volume of a substance and calculates its density as 1.40 g/mL. The correct, or accepted, value of the density is 1.30 g/mL. What is the percentage error of the student’s measurement?

5. Chapter 2 Error in Measurement
Section 3 Using Scientific Measurements
Chapter 2
Error in Measurement
Some error or uncertainty always exists in any measurement.
skill of the measurer
conditions of measurement
measuring instruments

6. Section 3 Using Scientific Measurements
Chapter 2
Significant figures - consist of all the digits known with certainty plus one final digit, which is somewhat uncertain or is estimated.
The term significant does not mean certain.

7. Reporting Measurements Using Significant Figures
Section 3 Using Scientific Measurements
Chapter 2
Reporting Measurements Using Significant Figures

8. Chapter 2 Determining the Number of Significant Figures
Section 3 Using Scientific Measurements
Chapter 2
Determining the Number of Significant Figures

9. Chapter 2 Sample Problem D
Section 3 Using Scientific Measurements
Chapter 2
Sample Problem D
How many significant figures are in each of the following measurements?
a g
b cm
c. 910 m
d L
e kg

10. Chapter 2 Significant Figures Rounding
Section 3 Using Scientific Measurements
Chapter 2
Significant Figures
Rounding

11. Chapter 2 Addition or Subtraction with Significant Figures
Section 3 Using Scientific Measurements
Chapter 2
Addition or Subtraction with Significant Figures
Least precise place value
Multiplication or Division with Significant Figures
Least total significant figures

12. Section 3 Using Scientific Measurements
Chapter 2
Addition or Subtraction with Significant Figures
15.78 g g
Answer will go by lowest placeholder.
Multiplication or Division with Significant Figures
Answer will have the same as the least total significant figures.
15.78 g x 3.1 g

13. Chapter 2 Sample Problem E
Section 3 Using Scientific Measurements
Chapter 2
Sample Problem E
Carry out the following calculations. Express
each answer to the correct number of significant
figures.
a m m
b. 2.4 g/mL  mL

14. Chapter 2 Conversion Factors and Significant Figures
Section 3 Using Scientific Measurements
Chapter 2
Conversion Factors and Significant Figures
Disregard conversion factors when determining significant figures.

15. Section 3 Using Scientific Measurements
Chapter 2
Scientific notation - numbers are written in the form M  10n, where the factor M is a number greater than or equal to 1 but less than 10 and n is a whole number.
example: mm = 1.2  104 mm

16. Chapter 2 Scientific Notation Convert into scientific notation:
Section 3 Using Scientific Measurements
Chapter 2
Scientific Notation
Convert into scientific notation:
47,532 g m s

17. Chapter 2 Mathematical Operations Using Scientific Notation
Section 3 Using Scientific Measurements
Chapter 2
Mathematical Operations Using Scientific Notation
1. Addition and subtraction —These operations can be performed only if the values have the same exponent (n factor).
example: 4.2  104 kg  103 kg or

18. Chapter 2 Mathematical Operations Using Scientific Notation
Section 3 Using Scientific Measurements
Chapter 2
Mathematical Operations Using Scientific Notation
2. Multiplication —The M factors are multiplied, and the exponents are added algebraically.
example: (5.23  106 µm)(7.1  102 µm)
= (5.23  7.1)(106  102)
=  104 µm2
= 3.7  105 µm2

19. Chapter 2 Mathematical Operations Using Scientific Notation
Section 3 Using Scientific Measurements
Chapter 2
Mathematical Operations Using Scientific Notation
3. Division — The M factors are divided, and the exponent of the denominator is subtracted from that of the numerator.
example:
=  103
= 6.7  102 g/mol

20. Chapter 2 Sample Problem F
Section 3 Using Scientific Measurements
Chapter 2
Sample Problem F
Calculate the volume of a sample of aluminum
that has a mass of kg. The density of
aluminum is 2.70 g/cm3.

21. Chapter 2 Direct Proportions
Section 3 Using Scientific Measurements
Chapter 2
Direct Proportions
Two quantities are directly proportional to each other if dividing one by the other gives a constant value.

22. Section 3 Using Scientific Measurements
Chapter 2
Direct Proportion

23. Chapter 2 Inverse Proportions
Section 3 Using Scientific Measurements
Chapter 2
Inverse Proportions
Two quantities are inversely proportional to each other if their product is constant.

24. Section 3 Using Scientific Measurements
Chapter 2
Inverse Proportion