Drill – 9/14/09 How many significant figures: Now complete the back of the measurement worksheet from last week (the graduated cylinder side)

Drill – 9/8 Measure (grad cylinder in mL)

Significant Figures

What is a Sig Fig? A number that means something in terms of the measurement tool used to obtain them. It tells you about the precision of the measuring device

You will use significant digits ALL YEAR on EVERY problem that you do!

The rules for significant digits Any number 1-9 IS significant (i.e. not zero) Zeros have special rules depending on where it is and if there is a decimal point Leading Zero Included Zero Final Zero

The rules for significant digits Any number 1-9 IS significant Zeros have special rules depending on where it is and if there is a decimal point. –Any included zero between two other numbers IS significant –If there is not a decimal point, then any final zero IS NOT significant –If there is a decimal point, then any final zero IS significant –If there is a decimal point, then any leading zero IS NOT significant

Math with Sig Figs Any time you do a calculation, you must make sure your answer is written with the correct number of significant figures!

Rules for × and ÷ When multiplying or dividing numbers, the answer can have no more significant figures then there are in the measurement with the fewest sig figs. When ever you need to “get rid” of non significant figures, you round the number to the correct number of significant figures

10.cm × 4.00cm = 40.cm 11.00g ÷ 0.35 mL = 31 g/mL g × 6.0g = 740g g × 6g = ?

Addition & Subtraction with Sig Figs When adding or subtracting decimals, the answer must go to the same “place” as the measurement with the least precise “place”. Ex: 25.1 g g = 27.1 g 1 digit to the right of the decimal 2 digits to the right of the decimal So there can only be one digit to the right of the decimal

400.5 g g = g 401 mL mL = 404 mL 10.0 g g = 144 cm cm 3 = 11.0 g 144 cm 3