Ionic Phenomena:

Ionic Phenomena: ^{A Study}

of an Environmental Problem

PSC-4012-2

Learning Guide

OF AN

E

P

PSC-4012-2

L

G

two courses are:

PSC-4010-2 Nuclear Technology: A Matter of Energy PSC-4011-2 Electricity: What's the Connection?

Author: Danielle Ouellet

Updated Version: Ronald Mongeau

Céline Tremblay

Program Coordinators at the DFGA: Serge Leloup Pierrette Marcotte

Production Coordinator at SOFAD: Jean-Simon Labrecque

Production Coordinator (1st edition): Mireille Moisan

Production Coordinator at the DFGA: Pauline Pelletier

Content Revisor: Céline Tremblay (French Version) John Allen (English Version)

Verification of Experiments: Annick Charlebois

Illustrations: Jean-Philippe Morin

Graphics: Science-Impact

Layout: Sylvain Nadeau

Translation and Linguistic Revision: Direction de la production en langue anglaise Services à la communauté anglophone Ministère de l'Éducation

First edition: September 1998

The preliminary version of this guide was produced by the Direction de la formation générale des adultes (DFGA). After this course was field-tested, the guide was updated by SOFAD.

André Dumas Commission scolaire catholique de Sherbrooke

Janine Gomel Direction du développement de la formation à distance Serge Marcil Commission des écoles catholiques de Montréal

Almas Simard Commission scolaire de Chicoutimi

Céline Tremblay Consultant, FormaScience

We would also like to thank the following teachers, who helped field-test the preliminary version of this document:

Suzy Asselin Commission scolaire catholique de Sherbrooke Lyne Desranleau Commission scolaire Saint-Jean-sur-Richelieu

Danielle Houde Commission scolaire de Chicoutimi

Ronald Mongeau Commission scolaire du Sault-Saint-Louis

© Société de formation à distance des commissions scolaires du Québec

All rights for translation and adaptation, in whole or in part, reserved for all countries. Any reproduction by mechanical or electronic means, including microreproduction, is forbidden without the written permission of a duly authorized representative of the Société de formation à distance des commissions scolaires du Québec.

Legal Deposit–1998

Bibliothèque et Archives nationales du Québec Bibliothèque et Archives Canada

ISBN 978-2-89493-126-4

GENERAL INTRODUCTION

Overview

The Physical Science Program ... 0.13 Ionic Phenomena: A Study of an Environmental Problem ... 0.13 Objectives ... 0.14 How to Use This Learning Guide ... 0.21 Information for Distance Education Students ... 0.23 Work Pace ... 0.23 Materials ... 0.23 Learning Activities ... 0.24 Experiments ... 0.24 Exercises ... 0.25 Self-Evaluation Test ... 0.25 Your Tutor ... 0.25 Homework Assignments ... 0.26 Certification ... 0.26 Useful Information ... 0.27 Mathematical Prerequisites ... 0.28 How to Round Off a Number ... 0.28 The Metric System... 0.29 An Important Property of Proportions ... 0.30 Formulas ... 0.31 Scientific Notation ... 0.32 Ionic Phenomena: A Study of an Environmental Problem ...0.33

LEARNING ACTIVITIES

Chapter 1: Poison from the Sky

Problems Related to the Use of Chemicals ... 1.6 Water Pollution Problems ... 1.7 A Country Built on Water Resources ... 1.7 Atmospheric Pollution Problems ... 1.11

The Ozone Layer ... 1.11 The Greenhouse Effect ... 1.13 Acid Rain ... 1.14 Case Study ... 1.16 Case-Study Outline ... 1.18 Defining the Problem... 1.19 Determining the Consequences ... 1.19 Analyzing the Solutions ... 1.19

- the first chapter.

Experiment 1.1 One method of recognizing

acidic substances ... 1.21 Acid Rain: How Long Have We Been Talking about It? ... 1.23 Acid Rain around the World ... 1.24 During Prehistory ... 1.24 In Greece ... 1.25 In the Czech Republic ... 1.26 In South Africa ... 1.27 In Canada ... 1.27 Acid Precipitation: What is the Situation in Québec? ... 1.29 Is It Possible to Reduce Acid Precipitation? ... 1.29 Understanding the Nature of Acid Precipitation ... 1.29 Key Words in this Chapter ...1.31 Summary ...1.31 Review Exercises ...1.32

Chapter 2: The Secrets of Matter

The Atomic Model ... 2.3 What Is a Model? ... 2.3 The Simplified Atomic Model ... 2.4 Energy Levels ... 2.7 Simplified Notation ... 2.8 The Classification of Elements ... 2.10 Nomenclature and Symbols... 2.10 Elements Follow an Order ... 2.13 The Modern Periodic Table ... 2.15 Practical Notation ... 2.18 Discovering the Logical Relationships ... 2.21 Metals, Nonmetals, and Metalloids ... 2.26 The Main Chemical Families ... 2.27 Key Words in this Chapter ...2.33 Summary ... 2.33 Review Exercises ... 2.36 Appendix: List of Elements ... 2.40

The Origin of Chemistry ... 3.5 Bonds Between Atoms ... 3.6 How and Why? ... 3.9 Ionization ... 3.12 The Lewis Diagram ... 3.19 Neutral Atoms ... 3.20 Ions ... 3.21 How Molecules Are Formed ... 3.23 Chemical Bonds ... 3.26 Ionic Bonds ... 3.27 Molecular Formulas ... 3.31 Covalent Bonds ... 3.34 Electronegativity ... 3.41 Difference in Electronegativity...3.44 Key Words in this Chapter ...3.47 Summary ...3.47 Review Exercises ...3.49

Chapter 4: Naming and Classifying Compounds

New Nomenclature ... 4.4 Binary Compounds... 4.5 Binary Molecular Compounds—Two Nonmetals ... 4.5 Binary Ionic Compounds—Metal and Nonmetal ... 4.7 Traditional Nomenclature and Complex Ionic Compounds ... 4.12 Acids, Bases, and Salts ... 4.18 A Little Bit of History ... 4.21 First Theory ... 4.23 Second Theory ... 4.24 Third Theory ... 4.25 Dissolution ... 4.26 Experiment 4.1 Similar or different properties?... 4.26 Ionic and Molecular Dissolution... 4.29 Dissociation Equations ... 4.32 Electrolytes and Non-Electrolytes ... 4.32 A few Uses of Acids, Bases, and Salts ... 4.39 Key Words in this Chapter ...4.40 Summary ...4.40 Review Exercises ...4.42

Concentration ... 5.10 Concentration in Grams per Litre ... 5.10 The Mole ... 5.15 Molar Concentration, or Molarity ... 5.25 Dilution ... 5.30 pH: a Measurement of Acidity ... 5.36 Acid-Base Indicators ... 5.43 Experiment 5.1 Using acid-base indicators ... 5.44 Key Words in this Chapter ...5.52 Summary ...5.52 Review Exercises ...5.54

Chapter 6: Nothing Is Lost, Nothing Is Gained

A Little History ... 6.3 Balancing Equations ... 6.5 How to Balance an Equation ... 6.8 Stoichiometric Calculations ... 6.19 Acid-Base Neutralization ... 6.30 Experiment 6.1 What a meeting! ... 6.30 Neutralization Equations ... 6.33 Key Words in this Chapter ...6.37 Summary ...6.37 Review Exercises ...6.39

Chapter 7: Case Study: Acid Precipitation

Defining the Problem ... 7.3 Agents Responsible for Acid Rain ... 7.5 Natural Sources ... 7.6 Industrial Sources ... 7.7 Scientific Aspects ... 7.10 Chemical Reactions ... 7.10 The Water Cycle ... 7.15 Transboundary Pollution ... 7.16 Determining the Consequences ... 7.20 Environmental Consequences ... 7.21 Effects on Terrestrial Ecosystems ... 7.21 Effects on Aquatic Ecosystems ... 7.22 Social Consequences ... 7.24

Analyzing the Solutions ... 7.29 Inventory of Possible Solutions ... 7.30 Scientific and Technical Solutions ... 7.30 Political Solutions ... 7.35 The Feasibility and Limitations of the Proposed Solutions ... 7.39 Personal Solutions ... 7.41 Some Practical Advice from the Québec Government ... 7.42 Key Words in this Chapter ...7.45 Summary ... 7.45 Review Exercises ...7.47 Appendix 1: The Effects of Acid Rain ...7.55 Appendix 2: Socioeconomic Consequences of Acidification ...7.58 Appendix 3: Case Study: Acid Rain ...7.60 Appendix 4: Possible Solutions ...7.65 Appendix 5: Chronology of the Main Stages in Canada-U.S.

Negotiations on Acid Rain ...7.67 Appendix 6: Resolving the Acidification Issue ...7.69 Appendix 7: Prospectus ...7.71 Appendix 8: The Perfect Lawn Syndrome ...7.72

CONCLUSION

Summary ...C.3 Self-Evaluation Test ... C.5 Answer Key to the Self-Evaluation Test ... C.19 Answer Key to Chapter Exercises

Poison from the Sky ... C.29 The Secrets of Matter ... C.33 Matter in Action ... C.40 Naming and Classifying Compounds ... C.51 A Matter of Concentration ... C.58 Nothing Is Lost, Nothing Is Gained ... C.75 Case Study: Acid Rain ... C.83 Bibliography ... C.93 Glossary ... C.95

GENERAL INTRODUCTION

OVERVIEW

The Physical Science Program

Welcome to the module entitled Ionic Phenomena: A Study of an Environmental Problem, which is part of the Secondary IV Physical Science program. This program includes two additionnal modules: Nuclear Technology: A Matter of Energy, and Electricity: What's the Connection?

This science program was designed to help you learn the fundamentals of physics and chemistry. This basic knowledge will give you a better understanding of the social and technological realities of modern society, thereby helping you become an informed citizen. This program will also allow you to develop an interest in science and research and prepare you for optional Secondary V programs.

Ionic Phenomena: A Study of an Environmental Problem

Ionic Phenomena: A Study of an Environmental Problem is a learning guide designed to meet all the requirements of a Secondary IV course. Its identification number is PSC-4012-2. If you meet all the certification requirements described in the section entitled "Information for Distance Education Students," you will earn two credits for this course.

This module covers the main chemistry concepts and phenomena that are essential to an understanding of the problems related to the use of certain chemical products. It presents the different steps in a case study of the acid precipitation problem. The different causes of acid precipitation are discussed, as well as the phases in its formation.

In terms of society at large, the main development factors that have contributed to the gradual acidification of our watercourses are exam- ined. Lastly, students are encouraged to develop their ability to make value judgments regarding the choices that must be made to try to solve a problem that can no longer be ignored.

Objectives

Chapter 1: Poison from the Sky Chapter 2: The Secrets of Matter

Terminal Objectives Intermediate Objectives Describe the current simplified atomic

model.

Using the electron configuration of at least two elements, explain the relation- ship between the number of electrons in the outermost energy level and the element's group number, and also the relationship between the number of energy levels and the element's period number.

Describe the metals, the nonmetals and the elements of the following chemical families: the alkali metals, alkaline earth metals, halogens and noble gases.

Define a scientific model.

Give the characteristics of the cur- rent simplified atomic model.

Draw a diagram of the atoms of the twenty lightest elements.

Define the expression "chemical fam- ily" or "group" as it pertains to the peri- odic table.

Define the term "period" as it pertains to the periodic table.

Give the electron configuration of the first twenty elements in the periodic table, using shorthand notation.

State the relationship between the group number and the number of electrons in the outermost energy level.

State the relationship between the pe- riod number and the number of energy levels.

Indicate where the following elements are located in the periodic table: hydro- gen, the metals, the nonmetals and the chemical families (alkali metals, alka- line earth metals, halogens and noble gases).

Indicate the properties and uses of the metals and nonmetals.

Indicate the properties and uses of the alkali metals, alkaline earth metals, halogens and noble gases.

Distinguish between hydrogen and the alkali metals.

Chapter 3: Matter in Action

Terminal Objectives Intermediate Objectives Using the octet rule, explain the type of

chemical bond between two particular elements.

Distinguish between neutral atoms, ions and isotopes as regards the number of protons, neutrons and electrons they have.

Explain the formation of binary com- pounds, using a Lewis diagram and, if appropriate, structural formula rep- resentation.

Indicate the characteristics of the electron configuration of the noble gases (helium, neon and argon).

State the octet rule.

Determine the ionization levels of the first twenty elements in the periodic table.

Distinguish between ionic bonds, polar covalent bonds and non-polar covalent bonds.

Define the term "electronegativity."

Indicate the electronegativity associ- ated with ionic, polar covalent and non-polar covalent bonds.

Using the electronegativity table, determine the type of bond (ionic, polar covalent or non-polar covalent) between two given elements.

Determine the number of protons, neutrons and electrons of an element whose atomic number and atomic mass are known.

Determine the charge of an ion whose atomic number or chemical family is known.

Compare the electron configuration of an ion with that of the correspond- ing neutral atom.

Describe the isotopes of a given element.

Distinguish between atomic mass and mass number.

Identify anions and cations.

Determine the charge of each ion.

Represent the ions, using a Lewis diagram.

Determine the molecular formula of a binary compound.

Chapter 4: Naming and Classifying Compounds

Terminal Objectives Intermediate Objectives According to the new nomenclature,

give the name of a binary compound whose chemical formula is known or the chemical formula of a binary com- pound whose name is known.

According to the traditional nomencla- ture, give the name of a polyatomic compound whose chemical formula is known or the chemical formula of a polyatomic compound whose name is known.

Represent the compound formed by ionic or covalent bonds, using a Lewis diagram.

Represent the compound formed by covalent bonds, using structural for- mula representation.

Draw a diagram representing the chemi- cal reaction between an element from group I or II and an element from group VI or VII, using the current sim- plified atomic model.

Distinguish between an element and a compound.

Identify anions and cations.

Determine the charge of the anion and cation on the basis of the octet rule or the chemical family.

Determine the number of anions and cations necessary for the formation of a binary compound.

Know the principal suffixes used to des- ignate binary compounds in the new nomenclature.

Know the significance of the prefixes used to designate the number of a type of atom.

Know the method for naming a binary compound according to the new nomenclature.

Know how to write the formula of a binary compound according to the new nomenclature.

Know the principal suffixes used to des- ignate polyatomic compounds in the tra- ditional nomenclature.

Know the significance of the prefixes used to designate the number of a type of atom or of polyatomic ions.

Using characteristics and equations for dissociation, explain why a substance is an acid, a base or a salt.

On the basis of experimental results, classify a substance as a non-electro- lyte, a strong electrolyte, a weak elec- trolyte, a strong acid, a weak acid, a strong base, a weak base or a salt.

In molecular terms, explain the disso- lution in an aqueous solution of the following substances: non-electrolytes, strong electrolytes, weak electrolytes, strong acids, weak acids, strong bases, weak bases and salts.

Know the method for naming a polyatomic compound according to the traditional nomenclature.

Know how to write the formula of a polyatomic compound according to the traditional nomenclature.

Distinguish among the characteristics of acids, bases and salts.

Describe Arrenhius' ionization theory concerning acids and bases.

Distinguish among equations for the dissociation of acids, bases, and salts.

By conducting an experiment, distinguish between a molecular dissolution and an ionic dissolution.

By conducting an experiment, distinguish between an electrolyte and a non-electrolyte.

By conducting an experiment, distinguish between a strong electro- lyte and a weak electrolyte.

By conducting an experiment, distinguish between a strong acid and a weak acid.

By conducting an experiment, distinguish between a strong base and a weak base.

Distinguish between molecular dissolution and ionic dissolution.

Distinguish between electrolytes and non-electrolytes.

Distinguish between strong electro- lytes and weak electrolytes.

Distinguish between strong acids and weak acids.

Distinguish between strong bases and weak bases.

Chapter 5: A Matter of Concentration

Terminal Objectives Intermediate Objectives Classify a substance according to

whether it is a mixture or a pure sub- stance and, if a mixture, whether it is homogeneous, heterogeneous or a sus- pension and, if a pure substance, whether it is an element or a com- pound.

Compare solutions whose concentra- tions are expressed in different units.

Solve problems pertaining to dilution.

Indicate the two categories into which matter is classified.

Describe the three categories of mix- tures.

Indicate the two categories of pure sub- stances.

Distinguish between solvent and solute.

Distinguish between homogeneous mixture and heterogeneous mixture.

Give the definition and the equation for a concentration.

Given a mass in kilograms, express it in grams.

Given a volume in millilitres, express it in litres.

Solve problems about the concentra- tion of solutions expressed in terms of mass of solute per volume of solution.

Define the term "mole."

Calculate the molar mass of a com- pound on the basis of the atomic mass of its constituent elements.

Given a quantity of matter expressed in grams, convert it into moles and vice versa.

Solve problems about the concentra- tion of solutions expressed in moles per litre.

Given a volume of solution in millilitres, express it in litres.

Define the term "dilution."

State the mathematical relationship between the characteristics (volume and concentration) of the stock solution and those of the diluted solution.

Rank solutions whose acidity is expressed in different units.

Determine the pH range of a solution on the basis of data or results obtained from acid-base indicators whose turn- ing points are known.

Chapter 6: Nothing Is Lost, Nothing Is Gained

Terminal Objectives Intermediate Objectives Express various chemical reactions as

balanced equations.

Using stoichiometric calculations, determine the quantity of the substances involved in a chemical reaction.

Using equations, explain how neutral- ization can offer a solution to an acid- base imbalance.

Define the term "pH."

Given the pH of a solution, deter- mine whether it is acidic or basic.

Give the pH of a concentration of H⁺ expressed in moles per litre (mol/L) and vice versa.

Define the term "turning point."

Indicate the turning point of the acid- base indicators.

By conducting an experiment, deter- mine the turning point of acid-base indicators.

Distinguish between the reactants and the products in a chemical reaction.

Write the equation for a chemical reac- tion on the basis of a descriptive statement.

Balance chemical equations.

Verify the law of the conservation of matter on the basis of a balanced equation.

Balance the reaction equation.

Express in moles the proportions of the reactants and the products.

Express in grams the proportions of the reactants and the products.

Write the equations used for the dissociation constant of acids and bases.

Define the term "neutralization."

Write the balanced equation for the neutralization of a simple acid by a simple base.

Recognize the equations for neu- tralization.

Chapter 7: Case Study: Acid Precipitation

Terminal Objectives Intermediate Objectives Describe a problem related to the use of

chemicals.

Make a complete list of the conse- quences of a problem related to the use of chemicals.

Analyze potential solutions to a prob- lem involving the use of chemicals.

Evaluate articles about problems related to the use of chemicals by focusing on the description of the prob- lem, its consequences and the proposed solutions.

Describe the historical evolution of the problem.

Identify the chemicals that caused the problem.

Explain the scientific and technical fac- tors involved.

Indicate the environmental effects of the problem.

Indicate the social, political and eco- nomic consequences of the problem.

List the potential solutions.

Indicate the feasibility and limitations of each of the solutions proposed.

Assess the scientific, technical, social, political and economic value of the solutions proposed.

HOW TO USE THIS LEARNING GUIDE

This course applies the main principles of individualized learning, which encourage you to:

– take an active part in the learning process;

– take responsibility for your own progress;

– work at your own pace;

– put your knowledge and experience to use.

As you work through this course at your own pace, you will be able to identify your strengths and weaknesses, discover the reasons for any problems you may have and decide what steps you must take to resolve these problems so you can continue to make progress.

Throughout this course, you will be able to consult your teacher if you are experiencing any difficulty. He or she will provide you with advice, encouragement, and constructive comments and feedback, adapting these services to meet your specific needs.

This learning guide is divided into three parts: the general introduc- tion, the learning activities and the conclusion.

Part I provides a general introduction to the course, outlining its objectives and providing the information you will need to get started. It also includes a section entitled "Mathematical Prerequisites," which deals with the different concepts you should be familiar with before beginning this course.

Part II consists of the learning activities, which have been divided into seven chapters. Each chapter covers a certain number of themes using explanations, tables, illustrations, exercises, activities, and experiments.

Each chapter begins with a list of objectives and a diagram showing where the chapter falls within the course. It ends with a list of key words, a summary, and review exercises that will help you go over what you have learned. Complementary reading material is found in the appendices to chapters 2 and 7.

The last chapter provides a wealth of information on social issues. By reading the related articles found in the appendices, you will develop skills that will help you analyze particular situations.

This guide is organized in such a way that you must work through it chapter by chapter. The questions and exercises will help you evaluate your knowledge as you go along.

Throughout this guide, you will encounter different symbols, picto- graphs, and typefaces, which are explained below.

Bold Words mentioned for the first time are printed in bold and defined. In some cases, the initial definition is expanded on later and a more formal definition is given in the glossary section at the end of the guide. Most of these words are also found in the list of key words at the end of each chapter and in a special supplement where you must write your own definition of these terms.

A light bulb indicates additional information: this informa- tion is not part of the course as such and will not be covered on the final examination (summative evaluation).

A hand signals an "Activity." These sections will guide you through exercises designed to help you master the concepts you have studied.

A flask signals an "Experiment." In order to help you better understand different situations or account for different phenomena, you will be asked to perform experiments either in a laboratory or using the experiment kits provided by Formation à distance.

The conclusion, Part III, summarizes what you have learned in all the courses in the program. It also contains a self-evaluation test to help you determine whether you have mastered the subject matter of this course and are therefore ready to write the final examination. The conclusion also includes an answer key for the self-evaluation test, for the exercises in each chapter, and for the activities, experiments, and review exercises. A glossary containing definitions of the key words and a bibliography of the materials used to produce this learning guide completes Part III. You may wish to consult these books and publications for further information on the topics covered in this course.

Good luck!

INFORMATION FOR DISTANCE EDUCATION STUDENTS

This guide is the main work tool for this course and has been designed to meet the specific needs of adult students taking distance education courses.

Distance education is a flexible system with several advantages, one of which is the opportunity to work at your own pace in the comfort of your own home. This system does, however, involve certain challenges: you have to take responsibility for your own learning and motivate yourself to work at a steady pace.

Here are some tips that will help you in your work.

Work Pace

• Draw up a study timetable that takes into account your personality and needs as well as your family, work and other obligations.

• Try to study a few hours per week. You should break up your study time into several one- or two-hour sessions.

• Do your best to stick to your study timetable.

Materials

Have all the materials you need close at hand.

• Learning material: this guide, a notebook where you will summarize important concepts relating to the objectives (listed in the introduction to this guide), and the Key Words in Each Chapter supplement in which you will define in your own words the boldface terms that appear in this guide.

• Reference materials: a dictionary, a calculator.

• Miscellaneous material: a pencil for writing your answers and your notes on this guide, a coloured pencil for correcting your answers, a highlighter (or a pale-coloured felt pen) to highlight important ideas, an eraser, etc.

• The periodic table of the elements and the experiment kit that came with this guide.

Learning Activities

This guide includes theoretical sections, as well as practical activities in the form of exercises. These exercises come with an answer key. The guide also includes several experiments involving simple operations that you can perform with the experiment kit you received with this guide. It is important that you take the necessary time to carry out the different steps described because they will help you develop a clearer understanding of the theory being presented.

Start by skimming through each part of this guide to familiarize yourself with the content and main headings. Then read the theory carefully:

– Highlight the important points.

– Take notes in the margins.

– Look up new words in the dictionary.

– Summarize important passages in your own words, in your notebook.

– Study the diagrams carefully.

– In the supplement entitled Key Words in Each Chapter, write your own definition of the terms that appear in boldface in the text and compare your definitions with those given in the glossary.

– Write down questions relating to ideas you don't understand.

Experiments

In order to attain the course objectives, you are asked to do a number of experiments as part of the learning activities. These experiments are compulsory, which is why you were obliged to purchase an experiment kit when you ordered the learning guide. This kit contains several important items that are usually hard to obtain. However, you will still have to acquire a number of other items yourself.

• For Experiment 1.1: lemon and apple juice, vinegar, human urine and saliva samples, tap water, sodium bicarbonate (baking soda), Fantastik cleaner, and either rainwater or melted snow.

• For Experiment 4.1: rubbing alcohol, window cleaner with ammonia, table salt, sugar, vinegar, Fantastik cleaner, and demineralized water.

• For Experiment 6.1: vinegar, Easy-Off oven cleaner (liquid), two glasses, and two wooden stirrers (coffee stirrers or popsicle sticks).

Exercises

The exercises come with an answer key found in the coloured section at the end of this guide, following the self-evaluation section.

• Do all the exercises.

• Read the instructions and questions carefully before writing your answer.

• Do all the exercises to the best of your ability without looking at the answer key. Reread the questions and your answers and revise your answers, if necessary. Then, check your answers against the answer key and try to understand any mistakes you made.

• Complete a chapter before doing the corresponding review exercises.

Doing these exercises without referring to the lesson you have just completed is a better way of preparing for the final examination.

However, you are not required to memorize dates, numerical data, or researchers' names. What is important is that you form an overview of the subject, that you grasp the connections, and that you develop the ability to make sound judgments.

Self-Evaluation Test

The self-evaluation test is a step that prepares you for the final evaluation. You must complete your study of the course before attempting to do it. Reread your notebook and the definitions of the key words in each chapter. Make sure you understand how they relate to the course objectives listed in the General Introduction to this guide. Then do the self- evaluation test without referring to the main body of the guide or the answer key. Compare your answers with those in the answer key and review any areas you had difficulty with.

Your Tutor

Your tutor is the person who will give you any help you need through- out this course. He or she is available to answer your questions and correct and comment on your homework assignments.

Don't hesitate to contact your tutor if you are having difficulty with the theory or the exercises, or if you need some words of encouragement to help you get through this course. Write out your questions and get in touch with your tutor during his or her available hours. If necessary, write to him or her. Information about how to contact your tutor that is not already contained in this guide will be made available to you.

Your tutor will guide you in your work and provide you with the advice,

Homework Assignments

In this course, you will have to do three homework assignments: the first after completing Chapters 1 to 4, the second after completing Chapters 5 to 7, and the third after completing the self-evaluation test. In addition, the final homework assignment may contain questions covering the entire course.

These assignments will show your tutor whether you understand the subject matter and are ready to go on to the next chapter in the course. If your tutor feels you are not ready to move on, he or she will indicate this in your homework assignment, providing comments and suggestions to help you get back on the right track. It is important to read these corrections and comments carefully.

You must obtain an average of at least 60% on the three homework assignments to be entitled to write the examination that permits you to earn the credits for this course.

The homework assignments are similar to the examination. Since the exam will be supervised and you will not be able to use your notes, the best way to prepare for it is to do your homework assignments without referring to your learning guide and to take note of your tutor's corrections so that you can make any necessary adjustments.

Remember not to send in the next assignment until you have received the corrections for the previous one.

Certification

If you obtain an average of at least 60% on your homework assign- ments, you may write the examination that permits you to earn the credits for this course. The examination is divided into two parts.

Part I consists of a two-hour written examination made up of multiple- choice, matching, and short-answer questions. This part is worth 76% of your final mark. You will be provided with a periodic table that does not include the full names of the elements, as well as a list of the names and formulas¹ of the main polyatomic ions. You may also use a calculator.

Part II also consists of a written examination, but in the form of one or more essay questions that allow you to summarize what you have learned from the course in terms of your ability to carry out a case study. All pertinent information such as numerical data, tables, and reference documents will be an integral part of the exam. This second part is worth 24% of your final mark and is written in one 90-minute session.

Both parts of the examination will be supervised and you will not be allowed to refer to your course notes.

To earn the credits for this course, you must obtain a total mark of at least 60% for both parts of the examination. Your homework assignments will not count toward your final mark.

Useful Information

Number of credits: 2 credits at the Secondary IV level Course duration: approximately 50 hours of study Number of homework assignments: 3

Opportunity to revise and re-submit homework assignments: none Pass mark: average of 60% on the homework assignments

average of 60% on both parts of the final examination

MATHEMATICAL PREREQUISITES

Below is a review of the mathematical prerequisites or concepts that you must know in order to work through the module with ease. Read this section carefully, and if necessary, refer back to it as you work through the module.

How to Round Off a Number

There are different reasons for rounding off a number to the nearest unit, to the nearest tenth, or to any other place value. To begin with, let's look at the names of the positions occupied by the digits in a decimal number. For example, take the number 35 497.8621. The place values of its digits are read as follows:

D^ECIMALNUMBER 35 497.8621

To round off this number to any place value, use the following procedure:

• Identify the digit occupying the position corresponding to the required degree of accuracy.

• Identify the first digit to the right of the designated position:

– if it is 0, 1, 2, 3 or 4, then the digit in the designated position remains the same;

– if it is 5, 6, 7, 8 or 9, then the digit in the designated position should be increased by 1.

• All the digits to the right of the designated position:

– become zero if they are in the integral part of the number;

– disappear if they are in the decimal part of the number.

Integral part

{

3 5 4 9 7

units hundredstens thousands ten thousands

Decimal point

Decimal part

{

8 6 2 1

thousandths hundredths tenths

ten thousandths .

Example

Round off the number 35 497.8621 to the nearest unit, to the nearest tenth and to the nearest hundredth.

• To the nearest unit

The digit 7 is in the unit's place. The first digit to the right of 7 is 8; therefore, 7 (in the unit's place) is increased by 1 and becomes 8. All the other digits to the right of the unit's place disappear. The result is 35 498.

• To the nearest tenth

The digit 8 is in the first decimal place (the tenths). The first digit to the right of 8 is 6; therefore, 8 is increased by 1 and becomes 9. All the other digits to the right of the tenth's place disappear. The result is 35 497.9.

• To the nearest hundredth

The digit 6 is in the second decimal place (the hundredths). The first digit to the right of 6 is 2; therefore, 6 does not change. All the other digits to the right of the hundredth's place disappear.

The Metric System

Symbols of quantity and their units The result is 35 497.86.

Quantity Symbol Unit Symbol

Length Mass Molar mass Pressure

Amount of substance Temperature

Time Volume

l m M p n T or t t V

metre kilogram

kilogram per mole pascal

mole

kelvin or Celsius second

litre

m kg kg/mol Pa mol K or °C s L

Multiples and submultiples of SI units

Here are a few examples of how multiples are used.

1 kg = 1000 × 1 g = 1000 g 1 hg = 100 × 1 g = 100 g 1 dag = 10 × 1 g = 10 g 1 dg = 0.1 × 1 g = 0.1 g 1 cg = 0.01 × 1 g = 0.01 g 1 mg = 0.001 × 1 g = 0.001 g

An Important Property of Proportions

In any proportion, the product of the extremes is equal to the product of the means.

Since a proportion consists of two equal ratios, we can say that . In this case, if 1 and 8 are the extremes, and 2 and 4 are the means, then 1 × 8 = 2 × 4.

This property is extremely useful when we want to convert a quantity expressed in one unit of measurement to an equivalent quantity expressed

Prefix Symbol Multiplier

Exa- Peta- Tera- Giga- Mega- Kilo- Hecto- Deca- Deci- Centi- Milli- Micro- Nano- Pico- Femto- Atto-

E 10¹⁸ =

P 10¹⁵ =

T 10¹² =

G 10⁹ =

M 10⁶ =

k 10³ =

h 10² =

da 10¹ =

d 10^–1 =

c 10^–2 =

m 10^–3 =

µ 10^–6 =

n 10^–9 =

p 10^–12 =

f 10^–15 =

a 10^–18 =

1 000 000 000 000 000 000 1 000 000 000 000 000 1 000 000 000 000 1 000 000 000 1 000 000 1 000 100 10

0.1 0.01 0.001 0.000 001 0.000 000 001 0.000 000 000 001 0.000 000 000 000 001 0.000 000 000 000 000 001

1 2

4

= 8

Example

Express a 0.5 kg mass in grams.

We know from the preceding Metric System tables that 1 kg corresponds to 1000 g. We can then ask the following question:

if 1 kg corresponds to 1000 g, then 0.5 kg corresponds to ? g.

We can now state the following proportion:

By applying the property of proportions and solving the equation, we get:

1 kg × ? g = 1000 g × 0.5 kg

? g = 1000 g × 0.5 kg

? g = 500 g

A mass of 0.5 kg is therefore equivalent to 500 g.

Formulas

Writing formulas often involves applying the rules of geometry or the laws of physics. A formula generally contains several variables joined by an equal (=) sign. We often need to transform formulas in order to solve for one variable or another. This can be done by applying the rules for solving equations.

The formula used to determine the volume of a rectangular prism is V = l × w × h, where V is the volume, l the length, w the width and h the height. By knowing the length, the width and the height, we can determine the volume. But what formula can we use to determine the height?

Example

Given the formula V = l × w × h, what formula can we use to determine the height h?

To determine the height, we have to isolate the variable h in the equation. This can be done by dividing both sides of the equation by the same value and then simplifying the resulting equation.

1 kg 0.5 kg 1000 g

? g =

1 kg

V = l × w × h

This gives us the formula h = .

Scientific Notation

With scientific notation, we can express very large or very small numbers without using a long, cumbersome series of digits.

Let's first review the notation for different powers of 10.

10 000 = 10 × 10 × 10 × 10 = 10⁴ 1000 = 10 × 10 × 10 = 10³

100 = 10 × 10 = 10²

10 = 10 = 10¹

1 = 1 = 10⁰

0.1 = 1/10 = 1/10¹ = 10^–1 0.01 = 1/100 = 1/10² = 10^–2 0.001 = 1/1000 = 1/10³ = 10^–3 0.0001 = 1/10 000 = 1/10⁴ = 10^{– 4}

Any given number can be expressed in several ways. For example, the number 4560 can be written as follows:

4560 = 4560 × 1 = 4560 × 10⁰ 4560 = 456 × 10 = 456 × 10¹ 4560 = 45.6 × 100 = 45.6 × 10² 4560 = 4.56 × 1000 = 4.56 × 10³ 4560 = 0.456 × 10 000 = 0.456 × 10⁴

Scientific notation involves expressing a number as a power of 10 multiplied by a number greater than or equal to 1 and less than 10. In the example above, 4560 can be written as 4.56 × 10³ in scientific notation.

Here are some other examples of numbers expressed in scientific notation.

13 400 000 = 1.34 × 10⁷ 1994 = 1.994 × 10³

740 = 7.40 × 10² V ₌ l × w × h

l × w

= h l × w

V l × w

V l × w

IONIC PHENOMENA: A STUDY OF AN ENVIRONMENTAL PROBLEM Throughout history, human beings have always sought to understand the world around them. Over the centuries, they have learned to make use of the planet's resources. In their quest for knowledge and for control over the environment, they have developed industry, agriculture, transporta- tion, and medicine, among other accomplishments. Today, we live in an era of science and technology. Breakthroughs in these fields occur almost daily. One need think only of the great progress made in the field of informatics, both in the workplace and in the home; and of the major strides taken in medicine and both experimental and applied biotechnol- ogy. Science and technology are changing and shaping our way of life almost daily, not to mention our view of the world.

Major progress made in the field of communications also gives an increasing number of people access to all kinds of information. It is difficult to avoid the public debates generated by the consequences of scientific and technological development. We are much more inclined now to question science-related policies, the consequences of technologi- cal progress such as the squandering of our resources, the deterioration of our environment, the potential dangers of nuclear generating stations, and the threat of nuclear war. Developments in science and technology, as well as the interests, values, and social responsibilities of the people (including industrialists, researchers, politicians, and individuals) responsible for such developments, are often targets of criticism.

To make informed judgments, it is important to have a thorough understanding of the scientific principles underlying a given situation, and this often requires a basic knowledge of chemistry. This learning guide looks at scientific, technological, social, and economic factors that help us to understand the current debates taking place regarding different scien- tific developments and fuelling a process of reflection that can no longer be avoided. It does this by focusing on a case study that is specifically related to the issue of acid precipitation.

Chapter 1

Poison from the Sky

1. POISON FROM THE SKY Chemicals

Water and atmospheric pollution Case study: acid precipitation Introduction

IONICPHENOMEN A:

ASTUD

YOF

ANENVIRONMENTAL PRO

BLEM ^4. NAMING AND CLASSIFYING COMPOUNDS New nomenclature

Traditional nomenclature Acids, bases, and salts

Electrolytes and non-electrolytes 2. THE SECRETS OF MATTER

Simplified atomic model Elements

Periodic table Major chemical families

3. MATTER IN ACTION History

Ionization Lewis diagram Chemical bonds Electronegativity

5. A MATTER OF CONCENTRATION Classification of substances Solutions

Concentration pH

Acid-base indicators 6. NOTHING IS LOST, NOTHING IS GAINED

Balancing equations Stoichiometry Acid-base neutralization 7. CASE STUDY:

ACID PRECIPITATION The problem The consequences The solutions

Many people maintain that the benefits derived from developments in the field of chemistry have greatly simplified our daily lives. Cleaning products, plastics, paints, and textiles—all products of the chemical industry—have become increasingly important in the home. Modern farmers use synthetic chemicals to increase crop production and livestock productivity, as well as to protect both crops and animals against various blights and diseases. Chemical additives are used throughout the food industry to conserve food and enhance its appearance. Advances in chemistry also find application in the transportation, metallurgical, and pharmaceutical industries. In fact, modern society would have difficulty managing without chemistry and its technology. But what price must be paid for this heavy dependence on chemical products? In what state will our planet be when we hand it over to the next generation? In fact, Gaea¹ is in abysmal shape!

We have not inherited the Earth from our parents; rather, we are lending it to our children.(translation)

World Conservation Strategy

Lakes and rivers, both sources of drinking water, are contaminated as a result of human activity. Industrial and agricultural operations, as well as municipalities and individuals, often treat our watercourses like ordinary sewers. Nor has the atmosphere been spared: acid rain, the greenhouse effect, and holes in the ozone layer are now household words.

Pollution is a fact, as we are constantly being reminded by newspapers, magazines, radio, and television. It sometimes seems as if the sky is falling down on our heads. Worse still, our feeling of powerlessness is at times equalled only by our ignorance!

Our watercourses are brimming with chemical pollutants. Some of these pollutants, which are persistent to varying degrees, come from household wastewater and fertilizers. Others, such as heavy metals, pes- ticides, PCBs (polychlorinated biphenyls), and radioactive substances (to name but a few), remain in the aquatic environment for very long periods of time and are accumulating at an alarming rate. These chemicals are associated with a decline in the populations of aquatic environments, as well as with the appearance of deformities and cancers in fish and bird species. The white beluga of the St. Lawrence River—now an endangered species—is a case in point. And much could be said about the rising cost of treating water to make it fit for human consumption.

1. Gaea was a Greek goddess who personified the Earth, motherhood, and the universal

The holes in the ozone layer are increasing the risk of skin cancer.

The greenhouse effect could, according to a number of theories, raise the temperature of the Earth to the point of causing drought or even floods which, followed by the melting of the polar (Arctic) ice cap, could wipe out entire countries.² Acid rain is responsible for maple tree dieback, the deterioration of monuments and buildings in cities, as well as the disappearance of certain life forms in lakes. It is even thought that 80%

of the lakes in eastern Canada are acidic or on the way to becoming so.³ Most people agree that we must act, but disagree as to what we should do. Pollutants have long-term effects, causing problems as they accumulate. What measures must be taken and at what cost? Our leaders sit down together to discuss and decide on the best solutions, but for the individual person, it is not easy to sift through all the information given by the media. Also, pollution can be discussed from many different viewpoints, including science and technology, politics, economics, health, ecology, history, and meteorology.

We are a "chemical" society, using hundreds of chemicals in our normal daily activities: washing, eating, house-cleaning, tending the lawn and garden, and driving.

Of the almost 10 million chemicals known today, approximately 100 000 chemicals are used commercially.

Over 10 000 new chemicals are created each week.

Most toxic chemicals are discharged directly into our watercourses as waste, but many also enter the water after everyday use in the home, agriculture, and industry. They constantly change the chemical composition of our waters.

One way is seepage: the chemicals soak through the earth into the groundwater from waste disposal sites and agricultural lands, for example. Another way is runoff: the chemicals are washed into bodies of water from the land where they were used or spilled, or from the air into which they were emitted.

The chemicals can affect the taste, odour, and colour of water. Fish and wildlife can experience reduced fertility, genetic deformities, immune system damage, increased incidence of tumours, and death.

Many of the chemicals that enter the water are, even in minute amounts, toxic to human, plant, and animal life.

Pesticides, PCBs, and PSPs (polychlorinated phenols) are typical examples. Pesticides are used in agriculture, forestry, and homes. PCBs, although no longer used in new installations, are still found as insulators in older electrical transformers, and PSPs can be found in wood preservatives.

The very qualities which make them desirable for use—

toxicity and persistence, for instance—make them so harmful to the environment.

2. Another theory says that the greenhouse effect would cause a cooling of the Earth, given that CO2, one of the gases responsible for this phenomena, reflects the Sun's rays. However, there appears to be a general consensus that an increase in the quantity of carbon dioxide causes some increase in temperature.

3. For a general idea of the extent of the acid rain problem in Québec at the end of the 1980s, Source : Canada, Environmental Citizenship, Clean water: life depends on it! Freshwater series, A-3, Environment Canada, p. 5.

Toxic chemicals: the legacy of a chemical society

Below are translations of excerpts from French-language media articles dealing with some of the problems mentioned in the preceding paragraph. Match each excerpt with the point(s) of view expressed by the journalist.

A. Scientific and technological E. Ecological

B. Political F. Historical

C. Economic G. Meteorological

D. Medical

Excerpt Point of view

1. In 1986, Sutton had rainfall that was just like apple juice (La Presse, August 1, 1987).

2. Canada must step up its efforts to combat the pollution of the Great Lakes. So says the United States at the international conference taking place in Montréal (La Presse, May 14, 1993).

3. The earliest alarming observations of the increasingly acidic precipitation in Europe and eastern North America date back to the 1960s (Pour la science, October 1988).

4. Acid rain can fall many kilometres away from the sources of pollution (Pour la science, October 1988).

5. Noranda Mines Ltd. in Noranda, Québec, is one of the ten largest producers of sulphur dioxide (SO₂) in Canada (The Canadian Consumer, May 1983).

6. Canadians prove the link between the ozone layer and ultraviolet radiation (La Presse, November 12, 1993).

7. Acid rain is fast eroding our children's architectural heritage (La Presse, August 6, 1988).

8. Acid rain would appear to promote colon cancer (La Presse, March 2, 1988).

9. Child demands ban on pesticide use on Île-Bizard (La Presse, October 4, 1993).

10. Both whales and dolphins are endangered species (La Presse, May 17, 1994).

1.1

Using a dictionary, define the word "pollution."

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

The following two questions ask you to use both your intuition and personal knowledge to come up with possible answers. The answers have not yet been covered in the text. Try to find your own.

Identify one characteristic that is common to all the following phenomena: acid rain, greenhouse effect, holes in the ozone layer, and sources of water pollution.

________________________________________________________________________

________________________________________________________________________

Match each of the phenomena listed in 1.3 with the observations in the left-hand column of the table below. Note that, in some cases, more than one phenomenon may be mentioned.

Observation Phenomenon

Glass or paint that loses its shine Skin cancer

Automobile exhaust emissions Increase in ultraviolet radiation Death of fish in lakes

Maple tree dieback Global warming Beach closures

PROBLEMS RELATED TO THE USE OF CHEMICALS

In this guide we will touch on some of the problems related to the use of chemicals. The different forms of water and atmospheric pollution are often the consequences of human activity. Pollution is a complex phenomenon, and its impact on the environment, health, and the economy are equally complex. Also, there are as many solutions proposed to these problems as there are points of view in the various sectors affected.

1.2

1.4 1.3

In order to clearly pinpoint a problem related to the use of chemicals, we must examine it from several vantage points: scientific, technological, social, economic, ecological, political, even historical and ethical. We are therefore going to develop a strategy for analyzing these problems: our strategy will be the case study. However, let us first examine the nature of some of the atmospheric and water pollution problems we currently face, as well as the causes.

Water Pollution Problems

When we think of life, we immediately think of water. After all, Earth isn't called the "blue planet" for nothing. And didn't life on Earth begin in water? Even our bodies comprise mostly water. Water covers much of our planet, lies underground, and fills the atmosphere. Yet only a minute portion of this colourless liquid is both drinkable and accessible.

A Country Built on Water Resources

Our continent was largely colonized by means of its many watercourses. An ideal means of communication and travel, the Great Lakes, as well as the St. Lawrence River and its many tributaries, lent themselves to settlement along their shorelines. Agriculture became a fact of life along the tributaries of the main rivers. Cities sprang up, bringing with them industry and people. These vast water resources thus fostered and fuelled human activity. Today, such activity still depends on our water resources.

This marked growth in human activity alongside our watercourses has created its share of problems, however. The Great Lakes, St. Lawrence River, and Atlantic Ocean have been unfavourably compared with an immense sewage system. Over the last 100 years, more than 60 000 different chemicals have been dumped into the enormous basin formed by the Great Lakes. The St. Lawrence River serves as the primary sewer main for these chemicals and as a recipient for all the toxic pollutants generated by the activities of our neighbours upstream. Into this toxic stream feeds all the waste produced alongside the river, which in turn carries it to the vast trunk sewer, the ocean.

Figure 1.1

Toxic substances in the aquatic environment

Atmospheric fall-out from different sources contributes to water pollution. Diffusion, bubble transfer, and exchanges between ocean-bed sediment and the surface of the water illustrate the different routes taken by pollutants. This pollution is passed on to all living beings that make up aquatic flora and fauna.

Wet deposition

Dry deposition Volatilization

Absorption

Bubble transfer

Vertical and horizontal diffusion

Sediment-water diffusion Suspension

Partitioning in the atmosphere

Diagram adapted from Canada, Environmental Citizenship, Clean water: life depends on it! Freshwater series, A-3, Environment Canada, p. 5.

There are many sources of water contamination, but three types of human activity are the main sources of the problem: industrial, agricultural, and domestic.

Industrial waste contributes to the accumulation of the most highly toxic and long-lasting chemicals in our watercourses, such as petroleum products, heavy metals (lead, mercury, cadmium), and PCBs. Around the Great Lakes alone, no fewer than 42 sites have been identified as being highly contaminated by such products. This contamination is directly responsible for the decline in reproduction and the appearance of muta- tions in the animals affected, for beach closures, and for problems in water treatment. We are only beginning to recognize the enormity of the environmental, economic, and social costs of this contamination.

Agricultural activity also contributes significantly to the deterioration of our watercourses. Because of its geographic distribu- tion, the principal negative effect of this industry is to contaminate the tributaries of the major watercourses. Fertilizers, pesticides, and the organic matter found in manure, as well as water from dairies, return to the watercourses through run-off or leaching.⁴ Fertilizers foster the growth of algae, and the resulting increase in debris accelerates the aging of lakes.

The pesticides in food enter the food chain and are often associated with the onset of various types of cancer. Organic pollutants promote the growth of bacteria and viruses associated with certain health problems and the closure of public beaches.

Household activities lead to the discharge of mainly organic matter into the sewage system. Added to this is water from storm drains, which contains road maintenance products and other contaminants (petroleum products and cleaning products). Lastly, the many chemical products that we use on a daily basis join the list of industrial and agricultural pollutants and contribute to the problems mentioned earlier.

4. The passage from upper to lower soil horizons of certain elements that dissolve in water and thus percolate down into and contaminate groundwater reserves.

An endangered resource

Whatever we do or wherever we go, water is everywhere, and, at first glance, seems infinitely available. Covering nearly three-quarters of the Earth's surface in the form of oceans, rivers, streams, lakes, snow, and glaciers, it is also found in the atmosphere and underground.

It is estimated that the world has water reserves totalling 1386 million km³. Such vast quantities are hard to imagine! To give you an idea of just how much water this is, 1 km³ of water would fill 300 Olympic stadiums. Of this quantity, 95.1% takes the form of saltwater that is difficult to desalinate for human consumption. Freshwater makes up only 4.9% of the total volume, and most of this occurs in the form of ice or groundwater, making it virtually inaccessible.

Only 139 000 km³ of freshwater do not occur in the form of ice or groundwater. The human race therefore has only 0.01% (1/100 of 1%) of the total volume of water on Earth available to meet its needs. By way of comparison, if you could put all the water on our planet into a 45-gallon barrel, the portion that would be usable by humans would be less than one teaspoon.

Canada is rightfully famous for its freshwater reserves. Ask any of the tourists arriving at the airport for their main impression of Canada, and there's a strong chance that they will talk about its vast expanses of water. Lakes cover approximately 8% of the country's surface area, a proportion that is unmatched anywhere else in the world. Canada has 565 lakes with a surface area larger than 100 km². The Great Lakes alone, which straddle the Canada–

U.S. border, contain 22 700 km³ of water, or 25% of the freshwater in all the lakes on the planet. They are on par with Lake Baïkal in Siberia in this respect.

It is estimated that 9% of the world's freshwater reserves are located on Canadian territory, compared with 18% in Brazil, 9% in China, and 8% in the United States. Canada boasts some 120 000 m³ of freshwater per capita, an enormous figure compared with other regions of the world: the island of Malta, for example, has less than 100 m³ of freshwater per capita. Québec shares in Canada's wealth of water resources, with 10% of its surface area covered by freshwater.

An illusion of abundance

However, even though Canadians have abundant water reserves, it is important to realize that most of this water is located far from urban, agricultural, and industrial centres. In fact, two-thirds of Canada's freshwater resources flow northward into the basins of the Arctic Ocean and Hudson Bay, while 90% of the population lives within 300 km of the Canada–

U.S. border.

It is becoming increasingly difficult to secure our drinking water supplies from watercourses owing to the nature, quantity, and variety of the contaminants dumped into the environment as the result of urban, industrial, and agricultural activities. The use of new, non-biodegradable chemicals makes any natural purification process difficult, if not impossible.

Pollution from acid rain is another cause of the deterioration in water quality. In Québec, the effects of acid rain are felt mainly north of the St. Lawrence River. Of the 1253 lakes sampled, 50% are acidic or becoming so. The most drastically affected regions are the Côte-Nord, Outaouais, Mauricie, and Abitibi.

Source: André Saint-Hilaire, "La qualité de l'eau au Québec," in Protégez-Vous, Cahier spécial H₂0 (May 1995), pp. 4–5 (translation).

Atmospheric Pollution Problems

The main focus of this learning guide will be acid rain, but this problem will also be related to other types of atmospheric pollution.

Acid rain, the greenhouse effect, and the holes in the ozone layer are three of the consequences of atmospheric pollution. These phenomena are not all caused by the same type of polluters, however. We will look at the nature of each problem and the main polluters associated with it.

The Ozone Layer

The ozone layer of the atmosphere lies at between 15 and 35 kilometres of altitude. The ozone it contains protects terrestrial life from the Sun's ultraviolet rays. Formerly, aerosol sprays and certain foams contained chemical substances known as chlorofluorocarbons, or more commonly, CFCs. After recognizing the harmful effects of these chemicals on the ozone layer, we cut back on their use, and today their use is restricted almost exclusively to refrigeration systems. As their name indicates, they contain chlorine, fluorine, and carbon. Once released into the atmosphere, CFCs react with the ozone, which gradually disappears.

The net result is a thinning of the ozone layer. As this is the layer that protects us from ultraviolet radiation, the main consequence of its thinning may be, according to some scientific researchers, an increase in the inci- dence of skin cancer. The decline in agricultural production and the deficiencies of the human immune system⁵ may also be attributable to the decrease of ozone in the atmosphere. However, nothing is absolutely certain. Other scientists claim that ultraviolet radiation poses a threat if we are exposed too long to the Sun, and that we are wrong to associate skin cancers with the thinning of the ozone layer. Regardless of who is right and given that prevention is better than a cure, alternative solutions have been found and the consumption of CFCs has continued to decline ever since the relationship between CFCs and ozone was first established in 1982.

5. The system of reactions of the human body that enable it to resist the invasion of certain disease-causing agents (bacteria, microbes, viruses).

Figure 1.2

Thinning of the ozone layer

Without protection from the ozone layer, swimmers risk "frying" in the sun.

Canada United States

Earth

Ozone

UV radiation

The Greenhouse Effect

Certain gases serve the same function as windows in a greenhouse:

they allow light rays in but prevent infrared rays from escaping. The result is that heat accumulates in the greenhouse. Scientists, notably those at the Institut de physique de Berne in Switzerland, have successfully demonstrated that carbon dioxide (CO₂) is contributing significantly to the warming of Earth's climates. This is what is known as the greenhouse effect. The consequences could be very harmful. The poor countries of the Third World risk seeing their already-fragile agricultural lands eroded by global warming and drought. Even water reserves are threatened.

Hurricanes could become more severe and occur more frequently.

However, scientists are divided in their opinions of the consequences of the greenhouse effect. Some think that a portion of the increased carbon dioxide would be absorbed by the oceans and that this phenomenon would reduce the warming effect on the Earth's climates. One thing is certain, however—the consequences will be most undesirable. The increased quantities of CO₂ in the atmosphere are due mainly to the use of petroleum and its by-products, used mostly in transportation and thermal generating stations.

Figure 1.3

Greenhouse effect