Measurements in Experiments Chapter 1 Section 2 Part 1 – SI Units, Prefixes, Scientific Notation & Conversions

SI Units of Measurements When scientist do research, they must communicate the results of their experiments with each other and agree on a system of units for their measurements. Systeme International (SI) SI Standards Length – meter (m) Mass – Kilogram (kg) Time – Second (s)

SI Prefixes A list of the most common prefixes A complete list can be found on page 12 in the book or the formula sheet. Base units are meters, grams & seconds Power Prefix Abbreviation 1x10-12 pico- p 1x10-9 nano- n 1x10-6 micro- μ 1x10-3 milli - m 1x10-2 centi- c 1x10-1 deci- d 1x101 deka- da 1x103 kilo- k 1x106 mega- M 1x109 giga- G

Prefixes Prefixes allows us to define a quantity without having to write it in scientific notation. Example 3,000,000 meters could be written as 3x106 m or can be written as 3 Megameters using prefixes.

Scientific Notation Used in the scientific community to describe numerical data in a precise way. Commonly used when dealing with very large numbers, very small numbers or when significant digits are important. Numbers Greater than 1 Positive exponents Numbers Less than 1 Negative Exponents Examples: 1,000,00 seconds → 1x106 seconds 0.0001 meters→ 1x10-4 meters

Conversions Turn what you are converting into a fraction, if not already, by placing it over 1. If it is not already done, convert back to the base unit m – meters S – seconds g – grams The exponent is always written with the base unit. Make sure what you are converting to is in the numerator (top) Cancel out all possible units, make sure you are left with what you want; multiply all the numerators, then the denominators and divide. Don’t forget the units in the final answer!

Conversion Example Convert 12 grams to gigagrams. 12 𝑔 1 𝑥 1 𝐺𝑔 1𝑥 10 9 𝑔 =12𝑥 10 −9 𝐺𝑖𝑔𝑎𝑔𝑟𝑎𝑚𝑠

Problems Convert each of the following 2 dm to nanometers 16 grams to micrograms 0.75 km to centimeters 35 km/hr to m/s 55 mi/hr to m/s