SIGNIFICANT FIGURES AND METRIC CONVERSIONS To Round or not To Round????

Significant Figures Term used to describe the digits in a measurement that are known with confidence plus one that is estimated. Measurements are made to the limits of the instrument used. All measurements contain some uncertainty.

Rules for Counting Sig. Fig. In any measurement: 1) All nonzero digits count. 2) Zeros between digits count. 3) Initial zeros never count. 4) Final zeros count IF there is a decimal present.

Practice counting significant figures m mm 0.25 ml km 1.00 kg 50 °C kJ

Math with Sig. Fig. For addition and subtraction: 1) Line up the decimal pts. 2) Do the math. 3) Round the answer to the least accurate place value. 4) Don’t forget the units !!!

Math with Sig. Fig. For multiplication and division: 1) Do the math 2) Count the SF in each of the components. 3) Round the answer to the least number. 4) Don’t forget the units!

Practice 16.4 m m = g – 12.0 g = L L = 2.5 g x g = m / 18 m = L x L =

The Metric System Easier to use because it is a decimal system Every conversion is by some power of 10. A metric unit has two parts A prefix and a base unit. prefix tells you how many times to divide or multiply by 10.

Base Units Length - meter -more than a yard - m Mass - grams - about a raisin - g Time - second - s Temperature - Kelvin or ºCelsius K or C Energy - Joules- J Volume - Liter - half of a two liter bottle- L Amount of substance - mole - mol

Prefixes kilo k 1000 times deci d 1/10 centi c 1/100 milli m 1/1000 kilometer - about 0.6 miles centimeter - less than half an inch millimeter - the width of a paper clip wire

Converting within the metric system The metric system uses prefixes to change the size of the base unit (m, g, L) The prefixes are powers of ten It is possible to simply move the decimal point to make simple conversions

MAKING CONVERSIONS Given value x = Answer Ex. Change 3.5 m to mm 3.5 m x = 3,500 mm Conversion Factor(s) 1000mm 1 m