INTRODUCTION TO MEASUREMENT, THE METRIC SYSTEM, SCIENTIFIC NOTATION, and DIMENSIONAL ANALYSIS

UNITS OF MEASURE ARE IMPORTANT

UNITS OF MEASUREMENT

Example

METRIC SYSTEM Metric system (Le Systeme International d’ Unites) AKA “S.I.”– common units of measurement for everyone (else)  Based on multiples or divisions of base unit 10 (remember the Dewey decimal system?) Common metric units of measure for: Length meter Mass gram Volume Liter Time second Energy Joule

METRIC PREFIXES http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/

Metric Prefixes 106 105 104 103 102 101 100 10-1 10-2 10-3 10-4 10-5 10-6 Base unit Mega Kilo Deka centi deci milli micro Meter Liter gram

Measurement All measurements have some degree of error associated with them – we like to have high accuracy and high precision Accuracy: Being able to come up with the “correct” or “accepted” value Precision: Being able to come up with the same value repeatedly Low accuracy / High precision High accuracy / Low precision Low accuracy / Low precision High accuracy / High precision

Reading measurements Always report measurements to one more decimal place than you are able to measure with the given scale I.e. you estimate the last digit Always include the unit used to make the measurement – otherwise, your number is meaningless!! (ml, g, cm etc.) When reading liquid volumes, read from the bottom of the meniscus ruler Graduated cylinder

    Measurement •      Accuracy: Being able to come up with the “correct” or “accepted” value Precision: Being able to come up with the same value repeatedly Low accuracy / High precision High accuracy / Low precision   Low accuracy / Low precision    High accuracy / High precision

METRICS AND MEASUREMENT Described in terms of ACCURACY and PRECISION

METRICS AND MEASUREMENT Measurements can be: QUANTITATIVE: numerically represented and measured Ex. : length of hair = 4.7 cm, volume of soda = 356 mL QUALITATIVE: descriptive Ex. : color of hair = brown, taste of soda = sweet