chpt 1 Labs: Begin next week CHEMISTRY 121 What is Chemistry? Your responsibilities Instructor: Dr. McCullough

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1 CHEMISTRY 121 Instructor: Dr. McCullough About this course Math is only prerequisite Chem 121 is a Natural Science Core course Labs: Begin next week Rules of civility NO: Talking in class/texting/cell phones/laptops/ ipods/mp3 players/pdas, etc. OK: Asking Questions; Coming Late/ Leaving Early when necessary Your responsibilities Attending class Doing homework (online and from text) Getting help when needed Checking lab and lecture websites regularly Preparing for Lab/Completing prelab assignments Bringing calculator to labs and exams What is Chemistry? Chemistry: the science that examines the properties and behavior of matter. Matter: Anything with mass and volume. All matter consists of about 100 basic substances (ELEMENTS). Each element has a unique kind of ATOM. ELEMENT: An individual atom or a collection of atoms of the same type; each is represented by a symbol. ex. Cu or Au Properties of matter depend on the kinds of atoms present (composition) and the arrangement of the atoms (structure). FeS CaF 2 C /01/ htm 1

2 Chemists: Observe ordinary-sized objects Chemists Use the Scientific Method: Explain in terms of atoms = submicroscopic or atomic Represent with Symbols, Formulas and Equations H 2 O(s) H 2 O(l) H 2 O(g) Figure 1.15 This allows for the Classification of Matter 1. By appearance 2. By state - gas, liquid, solid 3. By behavior; physical and chemical Pure Substances - 1. Elements: cannot be separated into simpler substances by physical or chemical methods. 4. By composition: Element? Compound? Mixture? 2. Compounds: Two or more elements combined chemically Like elements, compounds cannot be separated into simpler substances by physical methods Unlike elements, compounds CAN be broken down further by chemical rx n Not all elements are equally important or abundant: Figure 1.6 Law of constant composition - Each compound always has the same elements in the same proportions by mass. 2

3 What is not a pure substance? Mixtures Know the name and symbol of elements in Table 1.2 (pg 6 in text) plus: barium, Ba chromium, Cr cobalt, Co gold, Au platinum, Pt nickel, Ni manganese, Mn strontium, Sr zinc, Zn Homogenous vs. Heterogeneous mixtures NASA's metric confusion caused Mars Orbiter loss NASA's Climate Orbiter lost September 23, 1999 (CNN) -- NASA lost a $125 million Mars orbiter because one engineering team used metric units while another used English units for a key spacecraft operation. "People sometimes make errors," said Edward Weiler, NASA's Associate Administrator for Space Science in a written statement. MEASUREMENTS measured quantities number + unit Scientific Units: metric Système International (SI) units: Must know the 3 most common SI base units length - meter (m) mass - kilogram (kg) time - second (s) Base units are used with metric prefixes: Know names and meanings of prefixes in Table 1.5, and be able to use in calculations. 3

4 Measured quantities contain numbers + units SI units preferred indicates type of measurement Numbers contain 2 types of information: 1. Magnitude 2. Reliability a. Precision b. Accuracy There are 2 kinds of numbers 1. Exact Known exactly by counting or by definition. 2. Inexact Have some uncertainty associated w/ them. Numbers obtained by measurement are ALWAYS inexact. Why? The Reliability of a measurement is indicated by the number of digits used to report it. Measurements are reported such that: They express the level of precision of the method Only the last reported digit is uncertain. Significant Figures - All reported digits, including the last (uncertain) digit are significant. Rules for sig figs: p in text 1. All nonzero digits are significant 2. Zeros are significant when: a. in middle of number b. at end of number AND to right of decimal point Sig Figs in Calculations Numbers without decimal places that end in zeros: A calculation cannot improve a measurement!! The zeros may or may not be significant! Solution? Use scientific notation. 1. Addition and Subtraction: watch decimal places in each quantity What s not a sig. fig? Zeros to the LEFT of the 1st nonzero digit 2. Multiplication and Division watch # of sig. figs. in each quantity Exact Numbers: treat as if they have an infinite number of sig. figs. 4

5 Derived units - Combinations of (SI) base units Dimensional Analysis= Use of Conversion Factors Average speed Volume Conversion Factor Conversion Factors are found in back of text Density = mass volume Phenylbutazone is an antiinflammatory drug given to horses. Dosage: 4 to 9 milligrams per kilogram of body weight per day, divided into 3 equal doses. Your horse weighs 985 pounds. How many grams per dose should you give him? 1 kg = lbs Remember: Must know ALL of these prefixes and how to use them: Fig Temperature Scales 5