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TOPIC: Significant Figures
Do Now: Round 9,023.856103 to the…
1.Tenths2.Ones3.Hundreds4.Thousandths 5.Thousands
We use significant figures when doing data
calculations in chemistry
Significant figures are important because they tell us how good the data we are using are.
Counting Significant Figures
using the Atlantic/Pacific Rule
• Look for a decimal– Decimal point absent = Atlantic Ocean– Decimal point present = Pacific Ocean
• Start counting from first non-zero number
How to count Significant Figures
X
X
Decimal point absent:• Start on Atlantic (right) side of #
•Start counting with first non-zero non-zero digit & count until reach end of #
5400 m has 22 sig figs5431 m
has 44 sig figs
Decimal point present:
• Start counting with first non-zeronon-zero digit & count until reach end of #
2545.300 g
0.004530 km
has 77 sig figs
has 44 sig figs
•Start on Pacific (left) side of #
Every once in a while:
5300 cm
A line above a zero means its significant
_
Let’s practice…get out your packet
Multiplication and DivisionMultiplication and Division
COUNT SIG FIG for each numberAnswer can only be as specific as least specific number.
Ex: if one number has 3 sig figs and the other has 5 sig figs, you answer can only have 3 sig figs
24.56 cm x 14 cm =
1. 343.84 cm2
2. 343.8 cm2
3. 343 cm2
4. 340 cm2
Answer: 340ONLY 2 SIG FIGS
4 sig figs 2 sig figs
Let’s practice…try number 1-3
Addition and SubtractionAddition and Subtraction
Underline lowest place value.Answer can only be as specific as the least specific number
Example
• 540 + 12.4 + 0.211 + 100 = 652.611Tens Tenths Thousandths Hundreds
Answer can only be as specific as the least specific number
More specific
Answer = 700
422.63 cm 29.472 cm 115.9 cm________________+
568.002 cm
568.00 cm
568.0 cm
568 cm
Answer: 568.O
hundredths
Tenths
Thousandths
Tenths