SI Base Units SI Base Units Length Meter (m) Time Second (s) Mass Gram (g) Current Ampere (A or amp) Temperature Kelvin (K) Luminous Intensity Candela (Cd) Amount of Substance Mole (mol) Prefixes to Memorize . femto f 10-15 pico p 10-12 nano n 10-9 micro µ 10-6 milli m 10-3 centi c 10-2 deci d 10-1 BASE UNITS BASE UNITS BASE UNITS deka da (or dk) 101 hecto h 102 kilo k 103 mega M 106 giga G 109 tera T 1012 Significant Digits Significant Figures You may be asked to round to 3 significant figures ( or possibly 4 or 5) But first you must know how to determine whether a number is considered significant Rule 1 1. All digits 1-9 are significant 789 3 sig figs 12587 5 sig figs 1.234 4 sig figs Rule 2 ~ BETWEEN Any zero between two significant digits is automatically significant 1003 4 sig figs 10.03 4 sig figs 1,000,007 7 sig figs Rule 3 ~ FINAL ZERO Any FINAL ZERO (after the decimal point) is significant. 12.30 4 sig figs 3.5768000 8 sig figs 4.0 2 sig figs Rule 4 ~ placeholder Any zero is insignificant if it is not between two sig digits nor the final zero after a decimal point. Theses zeros are called placeholders. 400 1 sig fig 10000 1 sig fig 789,600 4 sig figs 0.00059 2 sig figs 0.000590 3 sig figs Examples 30040 grams 4 sig figs The last zero is not significant 0.663 kg 3 sig figs The zero only located the decimal point and is not significant 20.05 L 4 sig figs 1500 mg 4 sig figs There is line over the final zero, so all digits are significant 0.0008 grams 1 sig fig The zeros are only place holders. They are not significant The End Let’s practice!