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