Measurements in Science

1. Measurements in Science

2. Measurement Standards • All measurements are comparisons to some standard • Standard measures are kept in a central location, such as the standard kilogram at the National Research Council (NRC) Laboratories in Ottawa Canada’s Kilogram : K74

3. Measurements describe quantities such as length, mass, or temperature. • A quantity is a property that can be measured and described by a number and a unit that names the standard used. • Science deals with relationships among quantities, and the rules of mathematics must be adapted to handle quantities. • Only like quantities can be added or subtracted. • Units are important because they name the quantity measured.

4. Metric (SI) Units • Scientists use Le Systeme International d’unites, or SI. • SI is a modification of the older metric system which was used in France. • SI has the same numerical base as the decimal number system:every unit in the system is ten times the size of the next smaller unit, just as every place in a multi-digit number has ten times the value of any place to its right. • SI units for various quantities are defined in terms of units for simpler quantities whenever possible. Le Grand K

5. SI Base Units

6. All SI units are derived from the base unit by using prefixes which stand for some multiple of ten • We will focus on: kilo, deci, centi, milli, micro (these should be memorized)

7. Using Unitary Rates • Centi- is the prefix meaning “one hundredth” • One centimetre is one-hundredth of a metre. • 1cm = 0.01m or 100cm = 1m

8. Derived Quantities • Base units are limited in describing all the quantities you observe.

9. Converting derived quantities 100cm = 1m 1m x 1m = 1m2 100cm x 100cm = 10 000 cm2 (100cm)2 = (1m)2 10 000 cm2 = 1m2