1. DO NOW
Pick up handout.
Get out Percent Error, Accuracy, and Precision Practice handout.

2. Percent Error, Accuracy, and Precision Practice
Go over.

3. ROUNDING NUMBERS
Sometimes you will be asked to round a number to a particular number of significant digits.
Rules for Rounding:
If the digit to the immediate right of the last significant figure is less than five, do not change the last significant digit  2.53
If the digit to the immediate right of the last significant figure is five or greater, round up the last significant figure  2.54

4. ROUNDING NUMBERS 45.601 g _______________ 0.00701 m _______________
Round these numbers to three significant figures. If it is already three, just rewrite it.
g _______________
m _______________
mg _______________
2.010 L _______________
78,621.0 mL _______________
m _______________

5. SCIENTIFIC NOTATION
Scientific notation is a way of writing numbers that makes it easy to handle very large or very small numbers.
Imagine having to write all the zeros associated with Avogadro’s Number – 6.02 x 1023!
602,214,130,000,000,000,000,000

6. SCIENTIFIC NOTATION To put a number in Scientific Notation
If the number is less than one, move the decimal to the right. The exponent is negative and equals the number of places you moved the decimal point.
 x 10-5
If the number is greater than one, move the decimal to the left. The exponent is positive.
1234  x 103

7. SCIENTIFIC NOTATION To take a number out of Scientific Notation
If the exponent is negative, move the decimal point to the left. The number is less than one.
4.567 x 
If the exponent is positive, move the decimal point to the right. The number is greater than one.
1.234 x  1234

8. SIGNIFICANT FIGURES IN CALCULATIONS
Measurements that include inherent uncertainty are often used in calculations.
In order to keep the appropriate level of uncertainty, simple rules for significant figures have been developed.
ADDITION and SUBTRACTION
The number of significant figures to the right of the decimal point in the final sum or difference is determined by the lowest number of significant figures to the right of the decimal point in any of the original numbers.
1.223
5.33
+ 0.5

9. SIGNIFICANT FIGURES IN CALCULATIONS
MULTIPLICATION and DIVISION
The number of significant figures in the final product or quotient is determined by the original number that has the smallest number of significant figures.
400 x 25 =

10. SIGNIFICANT FIGURES IN CALCULATIONS
cm cm m x m g g cm cm

11. HOMEWORK Do the back side of Metric Conversions handout due Monday.
Bring your logbook Monday.