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In both junior high and high school, I had trouble staying focused. Sue Grafton, U is for Undertow Copyright© The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 1 Chemistry: Methods and Measurement Denniston Topping Caret 6th Edition 1.1 The Discovery Process • Chemistry - The study of matter… – Matter - Anything that has mass and occupies space • A table • A piece paper – What about air? • Yes, it is matter 1.1 The Discovery Process Chemistry: • the study of matter • its chemical and physical properties • the chemical and physical changes it undergoes • the energy changes that accompany those processes • Energy - the ability to do work to accomplish some change 1.1 The Discovery Process MAJOR AREAS OF CHEMISTRY • Biochemistry - the study of life at the molecular level • Organic chemistry - the study of matter containing carbon and hydrogen • Inorganic chemistry - the study of matter containing elements, not organic • Analytic chemistry - analyze matter to determine identity and composition 1.1 The Discovery Process • Physical chemistry - attempts to explain the way matter behaves public health pharmaceutical industry CHEMISTRY food science medical practitioners forensic sciences 1.1 The Discovery Process THE SCIENTIFIC METHOD • The scientific method - a systematic approach to the discovery of new information Characteristics of the scientific process Observation Formulation of a question Pattern recognition Developing theories Experimentation Summarizing information 1.1 The Discovery Process 1.1 The Discovery Process Models in Chemistry • To aid in understanding of a chemical unit or system – a model is often used – good models are based on everyday experience • Ball and stick methane model – color code balls – sticks show attractive forces holding atoms together 1.2 Matter and Properties • Properties - characteristics of matter – chemical vs. physical • Three states of matter 1. gas - particles widely separated, no definite shape or volume solid 2. liquid - particles closer together, definite volume but no definite shape 3. solid - particles are very close together, define shape and definite volume Three States of Water (a) Solid (b) Liquid (c) Gas 1.2 Matter and Properties Comparison of the Three Physical States 1.2 Matter and Properties • Physical property - is observed without changing the composition or identity of a substance • Physical change - produces a recognizable difference in the appearance of a substance without causing any change in its composition or identity - conversion from one physical state to another - melting an ice cube Separation by Physical Properties Magnetic iron is separated from other nonmagnetic substances, such as sand. This property is used as a large-scale process in the recycling industry. 1.2 Matter and Properties • Chemical property - result in a change in composition and can be observed only through a chemical reaction • Chemical reaction (chemical change) - a process of rearranging, removing, replacing, or adding atoms to produce new substances hydrogen + oxygen Æ water reactants products 1.2 Matter and Properties Classify the following as either a chemical or physical property: a. Color b. Flammability c. Hardness d. Odor e. Taste 1.2 Matter and Properties Classify the following as either a chemical or physical property: a. Color - physical b. Flammability - chemical c. Hardness - physical d. Odor - chemical e. Taste - chemical 1.2 Matter and Properties Classify the following as either a chemical or physical change: a. Boiling water becomes steam b. Butter turns rancid c. Burning of wood d. Mountain snow pack melting in spring e. Decay of leaves in winter 1.2 Matter and Properties Classify the following as either a chemical or physical change: a. Boiling water becomes steam (ph) b. Butter turns rancid (ch) c. Burning of wood (ch) d. Mountain snow pack melting in spring (ph) e. Decay of leaves in winter (ch) 1.2 Matter and Properties • Intensive properties - a property of matter that is independent of the quantity of the substance - Density - Specific gravity - Battery voltage • Extensive properties - a property of matter that depends on the quantity of the substance - Mass - Volume - Battery capacity 1.2 Matter and Properties Classification of Matter • Pure substance - a substance that has only one component • Mixture - a combination of two or more pure substances in which each substance retains its own identity, not undergoing a chemical reaction 1.2 Matter and Properties Classification of Matter • Element - a pure substance that cannot be changed into a simpler form of matter by any chemical reaction • Compound - a substance resulting from the combination of two or more elements in a definite, reproducible way, in a fixed ratio 1.2 Matter and Properties Classification of Matter • Mixture - a combination of two or more pure substances in which each substance retains its own identity • Homogeneous - uniform composition, particles well mixed, thoroughly intermingled • Heterogeneous – nonuniform composition, random placement 1.2 Matter and Properties Classes of Matter a - pure substance b - homogeneous mixture c - heterogeneous mixture 1.3 Significant Figures and Scientific Notation • Information-bearing digits or figures in a number are significant figures • The measuring device used determines the number of significant figures a measurement has • The amount of uncertainty associated with a measurement is indicated by the number of digits or figures used to represent the information 1.3 Significant Figures and Scientific Notation Significant figures - all digits in a number representing data or results that are known with certainty plus one uncertain digit 1.3 Significant Figures and Scientific Notation Recognition of Significant Figures • All nonzero digits are significant • 7.314 has four significant digits • The number of significant digits is independent of the position of the decimal point • 73.14 also has four significant digits • Zeros located between nonzero digits are significant • 60.052 has five significant digits 1.3 Significant Figures and Scientific Notation Use of Zeros in Significant Figures • Zeros at the end of a number (trailing zeros) are significant if the number contains a decimal point. • 4.70 has three significant digits • Trailing zeros are insignificant if the number does not contain a decimal point. • 100 has one significant digit; 100. has three [but there is a better way to write this] • Zeros to the left of the first nonzero integer are not significant. • 0.0032 has two significant digits 1.3 Significant Figures and Scientific Notation How many significant figures are in the following? 1. 3.400 2. 3004 3. 300. [3.00 x 102] 4. 0.003040 1.3 Significant Figures and Scientific Notation Scientific Notation • Used to express very large or very small numbers easily and with the correct number of significant figures • Represents a number as a power of ten • Example: 4,300 = 4.3 x 1,000 = 4.3 x 103 1.3 Significant Figures and Scientific Notation • To convert a number greater than 1 to scientific notation, the original decimal point is moved x places to the left, and the resulting number is multiplied by 10x • The exponent x is a positive number equal to the number of places the decimal point moved 5340 = 5.34 x 103 • What if you want to show the above number has four significant figures? = 5.340 x 103 1.3 Significant Figures and Scientific Notation • To convert a number less than 1 to scientific notation, the original decimal point is moved x places to the right, and the resulting number is multiplied by 10-x • The exponent x is a negative number equal to the number of places the decimal point moved 0.0534 = 5.34 x 10-2 1.3 Significant Figures and Scientific Notation • Conversion to scientific notation will allow to write numbers with significant figures without the artificial period at the end of a number 100. can be written as 1.00x102 • The decimal period without a decimal number is actually wrong,so avoid it (legibility, end of sentence) • Also, write a zero before decimal point. 0.11 is correct, .11 is not