TOPIC: Significant Figures Do Now: Round 9, to the… 1.Tenths 2.Ones 3.Hundreds 4.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 # non-zeroStart counting with first non-zero digit & count until reach end of # 5400 m has 2 2 sig figs 5431 m has 4 4 sig figs

Decimal point present: non-zeroStart counting with first non-zero digit & count until reach end of # g km has 7 7 sig figs has 4 4 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 Division COUNT SIG FIG for each number Answer 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 = cm cm cm cm 2 Answer: 340 ONLY 2 SIG FIGS 4 sig figs 2 sig figs

Let’s practice… try number 1-3

Addition and Subtraction Underline lowest place value. Answer can only be as specific as the least specific number

Example = Tens Tenths Thousandths Hundreds Answer can only be as specific as the least specific number More specific Answer = 700

cm cm cm ________________ cm cm cm 568 cm Answer: 568.O hundredths Tenths Thousandths Tenths