1. Significant Figures
The numbers that count

2. Reporting Measurements in Science
Accuracy of measurements depend on two things:
The skill of the person measuring
The capacity of the measuring equipment
Always read to the smallest mark and estimate one digit beyond
If smallest mark is in the tenths place then answer should be in the hundredths place

3. Numbers in Science Two types of numbers Exact: Measured:
ABSOLUTELY correct and obtained by counting
Have infinite # of sig figs
Measured:
Obtained by measuring
# of sig figs depend on person measuring

4. Rules for counting Sig figs
If the number is NOT a zero, IT IS significant
If it is a zero it’s sig only if:
It is between two other sig figs
Ends a number with a decimal
Rules for counting Sig figs
These are the basic rules to be followed when estimating
Sig Figs

5. Counting Sig Figs Identify # of Sig figs: 3.57
288
20.8
20.80
0.010
0.01
0.0100
3.20 x 104
If the number is NOT a zero, IT IS significant
If it is a zero it’s sig only if:
It is between two other sig figs
Ends a number with a decimal

6. Calculating Sig Figs: Addition & Subtraction
A calculated number CANNOT contain more sig figs than the measurements used to calculate it
round up or down to match measurement with the least number of decimal places
Example:
37.24 mL mL= 47.54mL
Answer: 47.5 mL

7. Calculating Sig Figs: Multiplication & Division
A calculated number CANNOT contain more sig figs than the measurements used to calculate it
Example:
1.23 cm x cm = cm2
Answer: 15.2 cm2
Round down or up to match number with the least # of sig figs

8. Reminders Always report measurements one place past measuring value
If using digital equipment report displayed amount (estimation has already been done)
25 dollars is an exact number
3.5 cm is an estimated measured number