1. Significant Figures/Significant Digits
(a.k.a. Sig-Figs or Sig-Digs)
There are two types of numbers: exact and inexact.
Exact numbers are counting numbers or defined quantities.
Ex. 12 eggs = 1 dozen
There are 26 letters in the alphabet.
EXACT NUMBERS ARE NOT TO BE CONSIDERED IN DETERMING
THE NUMBER OF SIGNIFICANT DIGITS FOR A CALCULATION.
Inexact numbers are based on measurements.
Ex. A person’s mass on a certain scale is kg.
The thickness of a certain sheet of metal is 1.23 mm.
These measurements are inexact because the precision using a
different type of instrument will influence the reading.
A person’s mass can be 63 kg, or kg
An instrument can read, 1.2 mm or mm.
The last digit in any measurement is an estimation, while
all other digits proceeding the last digit are known quantities.

2. Significant Figure Rules
1) Non-zero numbers are always significant.
2) Zeroes between two significant figures are always significant.
Ex kg L
3) All zeroes after both a significant figure and a decimal point are significant.
Ex m g
4) Leading zeroes are not significant.
Ex m kg
5) Trailing zeroes in integers with no decimal point are not significant?
Ex. 230,000 years cm/s
*How many significant figures are in each of the following?
a) 803 m b) kg c) ? d) 750,000

3. Accuracy/Precision
Accuracy: Closeness of a measurement to the standard value or accepted value of that quantity.
Precision: Degree of exactness of a measurement.
 = 3.14
Accurate numbers to : 3.12, 3.17, 3.16, 3.13, 3.15
Precise numbers to : 3.142, , ,
In measurements, precision refers to the how closely each measurement agrees.
Ex.: cm, 2.33 cm, 2.32 cm are precise measurements because they closely agree to each other with only ±0.01 cm deviation from the average.

4. Significant Figures Arithmetic
Addition/Subtraction:
Use the same number of decimal places as the least precise number in the calculations. m
m the least precise number with one decimal place m m
Ans: m the same number of decimal places as the least precise number in the calculation

5. Exceptions 7.000x103 m + 1.0 x102 m ------------------
7.1 x103 m Not the correct precision
x103 m
7.10 x 103 m answer
The smaller number must be converted to same
power of ten as the larger number and then the
precision can be compared.

6. Another example of the exception
4.0 x 103 mL
x mL
x 103 mL
x103 mL
4.0 x 103 mL answer

7. Multiplication/Division
Use the same number of significant figures as the number with the smallest number of significant figures.
Answer: 14 m/s
Since 4.3 s has the least number of significant figures between the two numbers, the answer will be expressed with two significant figures.