2.3 Using Scientific Measurements

Accuracy vs. Precision  Accuracy- closeness of measurement to correct or accepted value  Precision- closeness of a set of measurements

Accuracy vs. Precision

Significant Figures  All certain digits plus one estimated digit

Determining Number of Sig Figs  All non-zero numbers are sig figs  Zeros depend on location in number: LEADING zeros never count EMBEDDED zeros always count TRAILING zeros only count if there is a decimal point.

Location of Zeros 1. EMBEDDED: between non-zero numbers All are sig figs All are sig figs 2. LEADING: at front of all non-zero numbers None are sig figs None are sig figs 3. TRAILING: at the end of non-zero numbers If there is a decimal, all are sig figs If there is a decimal, all are sig figs If there is not, none are sig figs If there is not, none are sig figs

Practice EMBEDDED5 20.0TRAILING w/ LEADING TRAILING w/o TRAILING w/4

Rounding  Need to use rounding to write a calculation correctly  Calculator gives you lots of insignificant figures and you must round to the right place  When rounding, look at the digit after the one you can keep Greater than or equal to 5, round up Greater than or equal to 5, round up Less than 5, keep the same Less than 5, keep the same

Examples Make the following have 3 sig figs:   762   14.3   10.4     8020   204

Using Sig Figs in Calculations  Adding/Subtracting: end with the least number of decimal places end with the least number of decimal places

Using Sig Figs in Calculations  Adding/Subtracting: end with the least number of decimal places end with the least number of decimal places

Using Sig Figs in Calculations  Multiplying/Dividing: end with the least number of sig figs end with the least number of sig figs

Using Sig Figs in Calculations  Multiplying/Dividing: end with the least number of sig figs end with the least number of sig figs