Chemistry The Core Concepts Glenn V Lo Michael A Janusa Apago PDF Enhancer CHEMISTRY THE CORE CONCEPTS Apago PDF Enhancer Glenn V Lo Michael A Janusa Kona Publishing and Media Group Higher Education Division Charlotte, North Carolina Cover Design and Typesetting: diacriTech Copyright © 2010 by Kona Publishing and Media Group All rights reserved No part of this publication can be reproduced or transmitted in any form or by any means, electronic or mechanical, including photography, or any informational storage and retrieval system, without permission from the publisher All names of teachers, teacher learners, students and places are pseudonyms or are used with permission Teacher and student work samples are used with permission Apago PDF Enhancer Every effort has been made to contact the copyright holders for permission to reprint borrowed material We regret any oversights that may have occurred and will rectify them in future printings of this work ISBN: 978-1-935987-01-7 Library of Congress Control Number: ABOUT THIS E-TEXT This textbook is an attempt to provide a rigorous but learner-friendly introduction to Chemistry This textbook should serve the needs of science and non-science majors alike the very first concepts are defined in simple terms that even someone with a minimal background in science can understand the order of presentation of topics is meticulously chosen so that sufficient background has been provided by the time each new concept is introduced examples are immediately provided to illustrate and/or apply each new concept “test yourself ” questions provide additional reinforcement useful physics and math background/review, often relegated to appendices in typical textbooks, are integrated into the development of the topics A companion website (i-assign.com) provides: a links to videos explaining answers to “test yourself ” questions b study tips and links to useful and entertaining web resources c additional study questions that can be assigned as computer-graded homework For alternative sequencing of topics (for a typical first-semester course), it is useful to organize the chapters into the following learning units: Unit 1: Introductory Concepts (Ch 1–8) Unit 2: Atomic and Molecular Structure and Properties (Ch 9–16) Unit 3: Counting Atoms, Molecules, and Ions (Ch 17–20) Unit 4: Reactions in Aqueous Solutions (Ch 21) Unit 5: Molarity and solution stoichiometry (Ch 22) Unit 6: Ideal gas behavior and gas stoichiometry (Ch 23–26) Apago PDF Enhancer iii Units 2, 3, and may be covered in any order after Unit Units and must be covered before Unit Unit must be covered before Unit or Units and must be covered before Unit Units and must be covered before Unit The companion website, i-Assign.com, is a web-based homework delivery and collection system, as well as a test bank authoring system and test generator The automation afforded by i-Assign reduces a teacher’s workload while providing the following benefits By setting periodic deadlines for graded homework, teachers are able to encourage students to study on a regular basis and focus on a manageable amount of material Teachers can set up practice homework to give students more opportunities for mastery Homework and test individualization minimizes cheating Teachers can add their own questions Multiple versions of a test, which can be printed or delivered online, can be easily generated Apago PDF Enhancer iv About This E-Text TABLE OF CONTENTS Chapter 1: What is Chemistry? Chapter 2: Measurements Chapter 3: Atoms, Ions, and Molecules 29 Chapter 4: Basic Physics Concepts 43 Chapter 5: Classification of Matter 67 Chapter 6: The Periodic Table 79 Chapter 7: Compounds 89 Chapter 8: Chemical Changes 107 Chapter 9: History of Atomic Theory 127 Chapter 10: Quantum Theory 139 Chapter 11: Atomic Orbitals 155 Chapter 12: Electron Configuration 171 Chapter 13: Periodic Trends in Atomic Properties 183 Apago PDF Enhancer Chapter 14: Molecular Structure 195 Chapter 15: Quantum Mechanical Description of Molecules 225 Chapter 16: Intermolecular Forces 235 Chapter 17: The Mole Concept 247 Chapter 18: Molar Mass 253 Chapter 19: Elemental Analysis 263 Chapter 20: Stoichiometry 271 Chapter 21: Reactions in Aqueous Solutions 283 Chapter 22: Molarity and Solution Stoichiometry 303 Chapter 23: Ideal Gas Behavior 315 Chapter 24: Counting Gas Particles 329 v This page intentionally left blank Apago PDF Enhancer CHAPTER What is Chemistry? 1.1 Science Chemistry is a science, so we begin by defining science Science is a study that seeks to understand something based on empirical (or factual) information Major ideas in science are consistent with unbiased and verifiable facts; they are not mere opinions A more thorough way of defining science is to describe what scientists Scientists: • conduct research to acquire knowledge or solve problems • summarize knowledge into laws and theories • disseminate knowledge Apago PDF Enhancer 1.1.1 Scientific Research Scientists engage in research to acquire knowledge In doing so, they follow a procedure called the Scientific Method It involves the following: • Formulating the question or problem • Formulating a hypothesis • Conducting experiments to test a hypothesis • Analyzing experimental results and making a conclusion A hypothesis is a tentative answer to a question or problem and is defined as an educated guess What makes it educated? A scientist tries to find out as much of what is known or related to the problem before making a hypothesis This is done by reading scientific publications (the scientific literature), making observations, and relating the observations to what is already known from experience Observations or data are factual information based on what is sensed (seen, touched, heard, tasted, smelled) or measured A hypothesis must be testable It is tested by doing an experiment Observations made or data collected in an experiment should be reproducible Performing replicate measurements (multiple trials) is standard procedure in scientific work Things that could affect the outcome of an experiment are called variables A common type of research attempts to establish relationships between two variables In this case, a series of ▼ experiments is performed where one variable (the independent variable) is deliberately chosen as another variable is measured (dependent variable) When doing this type of research, it is important to try to identify all the other possible independent variables and hold all of those variables constant The analysis of experimental results should attempt to determine if they support the hypothesis The experimental results may be inconsistent with the hypothesis and lead one to a conclusion that the hypothesis needs to be rejected or revised If the hypothesis is revised, further experiments obviously need to be done Example A patient comes into a doctor’s office with an illness The first question that a doctor might try to answer is “what is the illness” (a) What would the doctor have to to formulate a hypothesis? (b) Suppose the doctor’s hypothesis is that the illness is something due to a certain type of bacteria What experiment could be done to test the hypothesis? Answers: (a) The doctor could examine the symptoms (patient’s temperature, rashes, etc ) and ask the patient about other symptoms, previous illnesses, medication the patient may be currently taking, etc The doctor could then relate the information to what he has learned from medical school and his experiences with previous patients The doctor could also refer to medical publications (b) There may be established laboratory procedures for detecting the presence of the bacteria in a blood or urine sample If the test turns out to be negative, then the doctor will have to come up with another hypothesis Apago PDF Enhancer 1.1.2 Disseminating Knowledge Sharing of information is important for the advancement of knowledge Once a scientist reaches a conclusion about a novel problem that others could find useful, it is important that the information be disseminated One way this is done is by writing a paper that describes the work The paper should not only present the results, but should also describe the procedures in sufficient detail so that other scientists can duplicate the experiments and verify the results The paper is then submitted for publication in scientific journals Reputable journals use a peer review process; articles submitted for publication are sent to other scientists to examine for reliability Chemistry: The Core Concepts 1.1.3 Laws and Theories Organizing and summarizing information are important for the advancement of knowledge Scientists these by formulating laws and theories A pattern tends to emerge when numerous related observations are examined A statement that summarizes the pattern is called a law (of nature) For example, the statement “heat naturally flows from a hot object to a colder one” is a law of nature For us to be able to say that this is a law, we must have made this observation numerous times Laws generally have no known exceptions at the time they are formulated Over time, exceptions might be found, but it is customary to still refer to the original statement as a law Oftentimes, the statement of a law specifies exceptions; such a law is called a limiting law A law can be written in the form of a mathematical equation; an example is the so-called ideal gas law, PV = nRT The ideal gas law is an example of a limiting law; it is only valid as P approaches zero The word theory is often mistakenly used when referring to a hypothesis This may be fine in layman’s terms, but not in science In science, theory and hypothesis are not the same A theory is a set of fundamental ideas that is consistent with everything (observations and laws) that is known about a subject These fundamental ideas are called postulates The postulates of a theory are assumptions; they cannot be proven to be true but they are accepted for as long as there are no known exceptions Laws with no known exceptions could be among of the postulates of a theory A theory becomes widely accepted (or well-established) if there is overwhelming evidence to support it All one needs to disprove a theory is one fact that contradicts one of the postulates of the theory However, should such an exception be found, it is typically not necessary to discard a theory; rather, one or more postulates is/are modified in order to account for the exception The more a theory has been modified, the more reliable it becomes So what is the difference between a hypothesis and a theory? A hypothesis is an educated attempt to explain or predict something A good way to come up with an educated explanation or prediction is to examine the known facts in light of a well-established theory If you do that, you could say that your hypothesis is a theoretical explanation or a theoretical prediction but it is not the theory Apago PDF Enhancer 1.2 Chemistry and Related Disciplines Chemistry is an example of a natural science In a natural science, the “thing” that we seek to understand is nature itself Other examples of natural sciences are physics, biology, geology, and astronomy Physics and Chemistry, the physical sciences, are both defined as the study of matter and its properties Matter is the stuff that the universe is made of; anything that has mass Chapter 1: What is Chemistry? ... deviations, divide the sum by N(N−1), then take the square root of the result If we calculate the standard error of the mean for the data in the preceding example, we find it to be 2.1 Thus, the uncertainty... deviation of the mean The formula for standard deviation of the mean is: N ∑( x − ) i=1 10 Chemistry: The Core Concepts i N ( N − 1) In this expression: • N is the number of trials • xi is the measured... reliability Chemistry: The Core Concepts 1.1.3 Laws and Theories Organizing and summarizing information are important for the advancement of knowledge Scientists these by formulating laws and theories