Transcript Significant Figures

Significant Figures
Warm - Up
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How do you use a fire extinguisher?
•
What should you do if you get a chemical in
your eyes? On your clothes?
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What should you do if you find or break
glassware in the lab?
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What is the role of the fire blanket in an
emergency situation?
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What is the difference between a
qualitative and a quantitative observation?
Objective
• Today I will be able to:
• Successfully identify lab equipment and safety
rules on a quiz
• Determine the number of significant figures in a
measurement
• Apply significant figures to solving problems
Homework
• Significant Figure Practice
• Dimensional Analysis Practice
Agenda
• Warm-Up
• Quiz
• Significant Figures Notes
• Significant Figures Practice
Significant Figures
AP Chemistry Special!
Significant Figures
• Measurements are frequently
combined
• Uncertainty of the separate
measurements must be reflected in
your final answer, which is done by
keeping track of the significant figures
in each separate measurement
Significant Figures
•Certain numbers and the
estimated digit of a
measurement
- Ex: 31.7 million has 3 sig figs –
two (3 and 1) are certain, and
one (7) is estimated
Atlantic Pacific Rule
Atlantic Pacific Rule
• If a decimal point is Present as in 52.3
km, count from the “Pacific Side” from
the first nonzero digit to the end.
Meaning, count from the left side of the
number
- 52.3 has 3 sig figs
- How many sig figs in .0093077
- There are 5 sig figs (start counting at 9)
Atlantic Pacific Rule
• If the decimal point is Absent, as in 1530
g, count from the Atlantic Side
beginning with the first nonzero digit
and going to the end, counting any zero
as significant. This means start from the
right
- 1530 g has 3 sig figs
• How many sig figs in 190,542,100ml
- There are 7 sig figs
Examples
• .0026702 m
-5
• 19.0750 kg
-6
• 25,000,000,000
mm
-2
• 1,908,150 L
-6
• 520 ml
-2
• .0102 ns
-3
Sig Fig Calculations
• You cannot be more precise than your
least precise measurement
• In multiplication and division, the
measurement with the smallest number
of sig digits determines how many digits
are allowed in the final answer
• If you have several steps, carry the extra
digits. Only the final answer is rounded
Examples
•6.15 m x 4.026 m = ?
- 6.15 m has 3 sig figs
- 4.026 m has 4 sig figs
- Your answer can only have 3 sig
figs
- 24.7599 m2  24.8 m2
Examples
•.03287 g x 45.2 g = ?
- .03287 g has 4 sig figs
- 45.2 g has 3 sig figs
- Your answer can only have three
sig figs
- 1.485724 g 
1.49 g
Sig Fig Calculations
• When adding or subtracting, the number of
decimal places in the answer should be equal
to the number of decimal places in the number
with the FEWEST places.
• 0.12 + 1.6 + 10.976 = 12.696
• 12.696  12.7 (a number with one decimal
place, because 1.6 has only one decimal place)
Whats the SIGnificance
• Swimming vs. Diving/ Gymnastics
Final Note
• When doing calculations with significant figures,
conversion factors do not figure in
• Counts and defined numbers are EXACT and have no
uncertain digits
• Example: if you say there are 6 people in your
family it is a counted number and is considered
certain. There are not 6.1 people in your family
• Example: 12 inches = 1 foot is defined – do not use
significant figures. 1 foot will never be 11.99
inches. In both cases, significant figures do not
apply
•Why are Significant
Figures Significant?
Exit Ticket