Introduction to Chemical Principles CHEMISTRY 31A Introduction to Chemical Principles Your Instructors and Teaching Assistants Mechanics of the Course

Powers of Ten and Scientific Notation Very large and very small numbers are common in science. MOVIE -- For more information on this topic, click on: http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/ Need to use a number between 1 and 10 times ten (10) raised to a positive or negative power called its exponent.

Addition, Subtraction, Multiplication, Division of Numbers in Scientific Notation Do some examples … …

Difference Between Accuracy and Precision An example from archery … …

Experimental Error A measurement without an error estimate is no measurement at all! Estimates and bounds have considerable value in science. A person with one thermometer thinks the temperature is known; a person with two or more thermometers knows that the temperature is not known but has a much better idea what the temperature is!

Random and Systematic Errors Random errors arise from a lack of precision. They are best estimated by replicate measurements and the use of statistics. Systematic errors arise from a lack of accuracy. They are best reduced by calibration against known reference standards.

Rules for Counting Significant Figures 1. Count all nonzero digits 2. Zeros that precede the first nonzero digit are never counted. 3. Zeros surrounded by nonzero digits are always counted. 4. Zeros that follow the last nonzero digit sometimes count and sometimes not, depending on whether they are present to position the decimal point or not. EXPAND. Zare’s Rule: Put quantity in scientific notation and count the number of digits in the number in front of ten raised to a power.

International System of Units; SI Units Quantity Unit Symbol Length meter m Mass kilogram kg Time second s Temperature kelvin K

Some Commonly Derived Units in the SI Unit System Area length x length m2 Volume length x length x length m3 Velocity length / time m / s Acceleration (length /time)/time m / s2 Force mass x acceleration kg m / s2 ≡ N Pressure force / area N / m2 ≡ Pa Energy force x distance N m ≡ J Power energy / time J / s ≡ W

The Standard Prefix Game of Modifiers   Factor Name  Symbol 10-1 deci d 10-2 centi c 10-3 milli m 10-6 micro µ 10-9 nano n 10-12 pico p 10-15 femto f 10-18 atto a 10-21 zepto z 10-24 yocto y Factor Name  Symbol 1024 yotta Y 1021 zetta Z 1018 exa E 1015 peta P 1012 tera T 109 giga G 106 mega M 103 kilo k 102 hecto h 101 deka da

The Standard Prefix Game of Modifiers   Factor Name  Symbol 10-1 deci d 10-2 centi c 10-3 milli m 10-6 micro µ 10-9 nano n 10-12 pico p 10-15 femto f 10-18 atto a 10-21 zepto z 10-24 yocto y Factor Name  Symbol 1024 yotta Y 1021 zetta Z 1018 exa E 1015 peta P 1012 tera T 109 giga G 106 mega M 103 kilo k 102 hecto h 101 deka da You need to learn the ones in red if you do not already know them.

Some Things are Dimensionless Numbers are dimensionless Numbers themselves come in groups: dozens grosses, moles Only exponentials and logarithms can be taken of numbers, so unit analysis becomes imperative.

Some Things have Dimensions A dimensioned quantity without its dimensions is no quantity at all! Don’t forget to express the units, where and when appropriate.

Converting from One Unit to Another and Keeping Track of What is Happening Example: Conversion of year into seconds …