1. Measurement & Significant Figures
Rules for Measurement
Significant Figures
Scientific Notation
Rounding in Science

2. I. Significant Figures
All the digits in a measurement up to the estimated digit are called significant figures
All numbers except zero are always significant
Zero is not considered significant when it is used as a place holder, that is when it wasn’t measured
Zeros is at the end of a non-decimal number are place holders and are not significant
Ex. 3,400mL Has 2 significant figures
Zeros at the beginning of a decimal number are also place holders and are not significant
Ex L Has 3 significant figures
Zeros between numbers are part of the measurement and are significant
Ex m Has 4 significant figures
Zeros at the end of a decimal were are not simply place holders and are part of the measurement; therefore, they are significant
Ex Has 3 significant figures

3. Comprehension Check
How many significant figures are in each number below?
3.250 g
4 Significant Figures
11.01cm
0.006g
1 Significant Figure
350mL
2 Significant Figures
0.25cm g
6 Significant Figures

4. I. Scientific Notation
Scientific Notation is a shorthand method for writing really large or small numbers
For example, the number below is an important number in chemistry called Avogadro’s Number 602,213,700,000,000,000,000,000 atoms in scientific notation the number is x1023 atoms
Writing a number is scientific notation does not change the value of the number, only its appearance
Move the decimal place to the right of the first significant figure
If moving the decimal place makes the number smaller, the power must increase to compensate
If moving the decimal place makes the number larger, the power must decrease to compensate

5. Comprehension Check Write the following numbers in scientific notation
1.002x1015 g
683,010,000,000,000,000,000 L
6.8301x1020 g g
2.03x10-8 g m
2.00x10-5 g
64,000,000,000,000,000,000,000,000m
6.4x1025 g

6. Rounding in Science
The number of significant figures reported tells everyone how accurate the measurements were
We never want to over or under report the accuracy of measurements
This means that we have to be careful when rounding answers to math problems
Rules for rounding answer to calculations
For multiplication and division
Round the final answer to same number of significant figures as the number with the least number of significant figures
For addition and subtraction – we’ll learn this later

7. Comprehension Check
Calculate the following and round the answers to the appropriate number of Sig Figs
10.333g / 3.1mL
g/mL  g/mL
37.25m2 / 11.58m
m  m
g ( mL/g)
mL  mL
1,250,000m ( s/m)
28.75 s  s