Sig. Figs continued Which numbers really matter? All non-zero numbers are significant. Example: 245, , Sandwiched zeros are significant. (Ex ) In order to determine whether other zero are significant, use the Atlantic/Pacific Rule Slide 2 of 6

PacificAtlantic

Significant Figures: The Atlantic/Pacific Rule Atlantic: –When a decimal point is Absent. Ignore any zeros to the right side of the last non-zero number to the right. P290,000 A P 10 A P209,090 A 2 Significant Figures 1 Significant Figures 5 Significant Figures Slide 3 of 6

Significant Figures: The Atlantic/Pacific Rule Pacific: –When a decimal point is Present. Ignore any zeros to the left side of the last non-zero number to the left. P A P A P A 4 Significant Figures 3 Significant Figures 5 Significant Figures Slide 4 of 6

Warning! When we say “ignore” we are not actually crossing them out and changing the number, we are just including only the numbers that count towards the precision of a measurement  This number stays the same although we say that there are four significant figures in the number. Slide 5 of 6

Sig. Fig Practice x , x ,000, Slide 6 of 6

Now you can count them.. Let’s do math with them… I will only ask you to multiply and divide with sig figs.

Multiplication/Division = 658 or sig. figs.  4 significant figures  3 significant figures x 5.35 x 5.35 The final answer will have: The same number of significant figures as the measurement with the least number of sig. figs.

Multiplication/Division Practice a)42.3 x 2.61 = b)0.61 x 42.1 = c)46.1 / 1.21 = d)23.2 / 4.1 =

Check Your Answers a)42.3 x 2.61 = 110. b)0.61 x 42.1 = 26 c)46.1 / 1.21 = 38.1 d)23.2 / 4.1 = 5.7

Density Density is a ratio of an objects mass to volume Density commonly has units of g/cm 3 or g/mL. –When doing conversions write as:

Density Examples A rock has a mass of 11.2 grams and a volume of 15 cm 3. Calculate its density.

Oil and Vinegar What do you observe when you mix oil and vinegar? Oil floats on top of the vinegar. The oil is less dense than the vinegar.