Chemistry 11 - McGraw-Hill Ryerson PDF

Ripped by Jack Truong, if you bought this, you got ripped off.  Matter and Chemical Bonding UNIT 1 CONTENTS CHAPTER 1 N ame ten things in your life...

Ripped by Jack Truong, if you bought this, you got ripped off.  Matter and Chemical Bonding UNIT 1 CONTENTS CHAPTER 1 N ame ten things in your life that do not, in some way, involve Observing Matter the products and processes of CHAPTER 2 chemistry. Take your time. Elements and the Periodic Table Are you having trouble? Can you name five things that do not CHAPTER 3 involve chemistry? Chemical Compounds and Bonding Are you still thinking? Consider CHAPTER 4 each room in your home. Think Classifying Reactions: about the bathroom, for example. Chemicals in Balance Does soap involve chemistry? Do toothpaste, cosmetics, and shampoo UNIT PROJECT involve chemistry? Think about Developing a Chemistry Newsletter the light in the bathroom. Without chemistry, there is no glass to make lightbulbs. UNIT 1 OVERALL EXPECTATIONS Move to another room. Walk quickly. The floor is disappearing What are the relationships among periodic trends, types beneath your feet. Pause briefly to of chemical bonds, and watch the paint fade away from the properties of compounds? walls. In a moment, the walls will How can laboratory investiga- be gone, too. tions help you represent the The story is the same if you step structures and interactions outdoors. There are no sidewalks, of chemicals in chemical vehicles, people, trees, or animals. reactions, and classify A world without chemistry is a these reactions? world without anything! Everything How can understanding the in the world, including you, is made properties and behaviour of up of matter. Chemistry is the study matter lead to the develop- of matter: its composition, its prop- ment of useful substances erties, and the changes it undergoes and new technologies? when it interacts with other matter. In this unit, you will explore matter. Unit Project Prep You will learn how to predict the Begin collecting ideas and kinds of bonds (the chemical resources for the project at the combinations) and the reactions end of Unit 1. that occur during these interactions. 2  Observing Matter I magine a chemical that is a key ingredient in most pesticides Chapter Preview 1.1 The Study of Chemistry contributes to environmental hazards, such as acid rain, the greenhouse effect, and soil erosion 1.2 Describing and Measuring Matter helps to spread pollutants that are present in all contaminated rivers, lakes, and oceans 1.3 Classifying Matter and is used in vast quantities by every industry on Earth Its Changes can produce painful burns to exposed skin causes severe illness or death in either very low or very high concentrations in the body is legally discarded as waste by individuals, businesses, and industries has been studied extensively by scientists throughout the world In 1996, a high school student wrote a report about this chemical, dihydrogen monoxide, for a science fair project. The information in the student’s report was completely factual. As a result, 86% of those who read the report — 43 out of 50 students — voted in favour of banning the chemical. What they did not realize was that “dihydrogen monoxide” is simply another name for water. What if you did not know that water and dihydrogen monoxide are the same thing? What knowledge and skills can help you distinguish genuine environmental issues from pranks like this one? What other strategies can help you interpret all the facts, opinions, half-truths, and falsehoods that you encounter every day? This chapter will reacquaint you with the science of chemistry. You will revisit important concepts and skills from previous grades. You will also prepare to extend your knowledge and skills in new directions. What mistake in measuring matter nearly resulted in an airplane disaster in 1983? Read on to find the answer to this question later in this chapter. Chapter 1 Observing Matter MHR 5  1.1 The Study of Chemistry Section Preview/ Many people, when they hear the word “chemistry,” think of scientists in Specific Expectations white lab coats. They picture bubbling liquids, frothing and churning In this section, you will inside mazes of laboratory glassware. identify examples of Is this a fair portrayal of chemistry and chemists? Certainly, chemistry chemistry and chemical happens in laboratories. Laboratory chemists often do wear white lab processes in everyday use coats, and they do use lots of glassware! Chemistry also happens every- communicate ideas related where around you, however. It happens in your home, your school, your to chemistry and its relation- community, and the environment. Chemistry is happening right now, ship to technology, society, inside every cell in your body. You are alive because of chemical changes and the environment, using and processes. appropriate scientific Chemistry is the study of matter and its composition. Chemistry is vocabulary also the study of what happens when matter interacts with other matter. communicate your When you mix ingredients for a cake and put the batter in the oven, that understanding of the is chemistry. When you pour soda water on a stain to remove it from your following terms: favourite T-shirt, that is chemistry. When a scientist puts a chunk of an chemistry, STSE ice-like solid into a beaker, causing white mist to ooze over the rim, that is chemistry, too. Figure 1.1 illustrates this interaction, as well as several other examples of chemistry in everyday life. A B Figure 1.1 A Frozen (solid) carbon dioxide is also known as “dry ice.” It changes to a gas at temperatures higher than −78˚C. In this photograph, warm water has been used to speed up the process, and food colouring has been added. B Dry ice is also used to create special effects for rock concerts, stage plays, and movies. C Nitrogen gas becomes a liquid at –196˚C. Liquid nitrogen is used to freeze delicate materials, such as food, instantly. C 6 MHR Unit 1 Matter and Chemical Bonding Chemistry: A Blend of Science and Technology Like all scientists, chemists try to describe and explain the world. Chemists start by asking questions such as these: Why is natural gas such an effective fuel? How can we separate a mixture of crude oil and water? Which materials dissolve in water? What is rust and why does it form? To answer these questions, chemists develop models, conduct experiments, and seek patterns. They observe various types of chemical reactions, and they perform calculations based on known data. They build continuously on the work and the discoveries of other scientists. Long before humans developed a scientific understanding of the world, they invented chemical techniques and processes. These tech- niques and processes included smelting and shaping metals, growing crops, and making medicines. Early chemists invented technological instruments, such as glassware and distillation equipment. Present-day chemical technologists continue to invent new equipment. They also invent new or better ways to provide products and services that people want. Chemical technologists ask questions such as the following: How can we redesign this motor to run on natural gas? How can we contain and clean up an oil spill? What methods can we use, or develop, to make water safe to drink? How can we prevent iron objects from rusting? D E D Green plants use a chemical process, called photo- synthesis, to convert water and carbon dioxide into the food substances they need to survive. All the foods that you eat depend on this process. E Your body uses chemical processes to break down food and to release energy. F Your home is full of products that are manufactured by chemical industries. The products that are shown here are often used for cleaning. Some of these products, such as bleach and drain cleaner, can be dangerous if handled improperly. F Chapter 1 Observing Matter MHR 7  Chemistry, Technology, Society, and the Environment Today we benefit in many ways from chemical understanding and tech- nologies. Each benefit, however, has risks associated with it. The risks and benefits of chemical processes and technologies affect us either directly or indirectly. Many people — either on their own, in groups, or through their elected government officials — assess these risks and benefits. They ask questions such as the following: Is it dangerous to use natural gas to heat my home? Why is the cost of gasoline so high? Is my water really clean enough to drink and use safely? How does rust degrade machinery over time? During your chemistry course this year, you will study the interactions among science, technology, society, and the environment. These interac- tions are abbreviated as STSE. Throughout the textbook — in examples, practice problems, activities, investigations, and features — STSE interac- tions are discussed. The issues that appear at the end of some units are especially rich sources for considering STSE interactions. In these simula- tions, you are encouraged to assess and make decisions about important issues that affect society and the environment. STSE Issue: Are Phosphates Helpful or Harmful? Phosphorus is an essential nutrient for life on Earth. Plants need phosphorus, along with other nutrients, in order to grow. Phosphorus is a component of bones and teeth. In addition, phosphorus is excreted as waste from the body. Thus, it is present in human sewage. Since phosphorus promotes plant growth, phosphates are excellent fertilizers for crops. (Phosphates are chemicals containing phosphorus. You will learn more about phosphates later in this unit.) Phosphates are also used as food additives, and as components in some medicines. In addition, they are an important part of dishwasher and laundry deter- gents. For example, sodium tripolyphosphate (STPP) acts to soften water, and keep dirt suspended in the water. Before the 1970s, STPP was a major ingredient in most detergents. Phosphates Causing Trouble In the 1960s, residents around Lake Erie began to notice problems. Thick growths of algae carpeted the surface of the water. Large amounts of the algae washed onto beaches, making the beaches unfit for swimming. The water in the lake looked green, and had an unpleasant odour. As time passed, certain fish species in Lake Erie began to decrease. In 1969, a joint Canadian and American task force pinpointed the Language source of the problem. Phosphates and other nutrients were entering the LINK lake, causing algae to grow rapidly. The algae then began to die and rot, Eutrophication is the process using up dissolved oxygen in the water. As a result, fish and other water in which excess nutrients in a species that needed high levels of oxygen were dying off. lake or river cause algae to The phosphate pollution arrived in the lake from three main sources: grow rapidly. Look up this term wastewater containing detergents, sewage, and run-off from farms carrying in a reference book or on the phosphate fertilizers. The task force recommended reducing the amount Internet. Is eutrophication of phosphate in detergents. They also suggested removing phosphorus at always caused by human wastewater treatment plants before the treated water entered the lake. action? Detergent manufacturers were upset by the proposed reduction in phosphates. Without this chemical, their detergents would be less effec- 8 MHR Unit 1 Matter and Chemical Bonding tive. Also, it would be expensive to develop other chemicals to do the same job. After pressure from the government, detergent companies reduced the amount of phosphate in their products by about 90%. Cities on Lake Erie spent millions of dollars adding phosphorus removal to their waste treatment. Today, Lake Erie has almost completely recovered. The connection between technology (human-made chemical products) and the environment (Lake Erie) is an obvious STSE connection in this issue. What other connections do you see? Canadians in Chemistry it is emitted in the infrared range of energy. It can be detected, however, with the right instruments. Dr. Polanyi’s work led to the invention of the laser. As well, his research helped to explain what happens to energy during a chemical reaction. Dr. Polanyi believes that people must accept the responsibility that comes with scientific understanding and technological progress. He believes, as well, that a vital element of hope lies at the heart of modern science. To Dr. Polanyi, human rights are integral to scientific success. “Science must breathe the oxygen of freedom,” John Charles Polanyi was born in Berlin, he stated in 1999. Germany, into a family of Hungarian origin. This is why Dr. Polanyi says that scientists Polanyi was born on the eve of the Great must take part in the debate on technological, Depression, shortly before the Nazi takeover. His social, and political affairs. Dr. Polanyi points father moved to England to become a chemistry to the political role played by scientists such professor at Manchester University. Polanyi was as Andrei Sakharov in the former Soviet Union, sent to Canada for safety during the darkest years Linus Pauling in the United States, and Fang Lizhi of World War II. in China. John Polanyi went back to England to earn a doctorate in chemistry at Manchester University Make Connections in 1952. He returned to Canada a few years later. 1. Research the scientists whom Dr. Polanyi Soon after, he took up a position at the University mentioned: Andrei Sakharov, Linus Pauling, of Toronto. There Dr. Polanyi pursued the and Fang Lizhi. What work distinguished them research that earned him a share of the Nobel as scientists? What work distinguished them Prize for chemistry in 1986. He pioneered the field as members of society? of reaction dynamics, which addresses one of the 2. Throughout history, chemists have laboured to most basic questions in chemistry: What happens present the truth as they know it to their fellow when two substances interact to produce another scientists and to society. Some of them, such substance? Polanyi’s father had once investigated as Linus Pauling, have been scorned and the same question. ridiculed by the scientific community. Do fur- Dr. Polanyi tried to provide some answers by ther research to discover two other chemists studying the very faint light that is given off by who have struggled to communicate their molecules as they undergo chemical changes. ideas, and have succeeded. This light is invisible to the unaided eye, because Chapter 1 Observing Matter MHR 9  COURSE Section Wrap-up CHALLENGE During this chemistry course, your skills of scientific inquiry will be assessed using the same specific set of criteria (Table 1.1). You will At the end of this course, you will have a chance to use what notice that all review questions are coded according to this chart. you have learned to help you in Table 1.1 Achievement Chart Criteria, Ontario Science Curriculum the Course Challenge: Planet Knowledge and Inquiry Communication Making Connections Unknown. In this challenge, Understanding (K/U) (I) (C) (MC) you are a member of a science team sent to a new planet. It is understanding application of communication understanding your task to analyze the plan- of concepts, the skills and of information of connections et’s resources. You will design principles, strategies of and ideas among science, and carry out hands-on investi- laws, and scientific technology, use of scientific gations and analyze your theories inquiry society, and the terminology, results. Then you will prepare environment knowledge of application of symbols, a presentation to persuade the facts and terms technical skills conventions, analysis of Canadian government to invest and procedures and standard social and transfer of in the establishment of a com- (SI) units economic concepts to use of tools, munity on the planet. As you issues involving new contexts equipment, and communication work through this book, keep a science and materials for different research portfolio of notes and understanding technology audiences and ideas that may help you in the of relationships purposes assessment of Course Challenge. between impacts of concepts use of various science and forms of technology on communication the environment use of proposing of information courses of technology for practical action scientific in relation to purposes science-and technology- based problems Section Review 1 K/U Based on your current understanding of chemistry, list five ways in which chemistry and chemical processes affect your life. 2 I Earlier in this section, you learned that fertilizers containing phosphorus can cause algae to grow faster. Design an investigation on paper to determine the effect of phosphorus-containing detergents on algae growth. 3 C Design a graphic organizer that clearly shows the connections among science, technology, society, and the environment. 4 MC For each situation, identify which STSE interaction is most important. (a) Research leads to the development of agricultural pesticides. (b) The pesticides prevent insects and weeds from destroying crops. (c) Rain soaks the excess pesticides on farm land into the ground. It ends up in groundwater systems. (d) Wells obtain water from groundwater systems. Well-water in the area is polluted by the pesticides. It is no longer safe to drink. 10 MHR Unit 1 Matter and Chemical Bonding Describing and Measuring Matter 1.2 As you can see in the photograph at the beginning of this chapter, water Section Preview/ is the most striking feature of our planet. It is visible from space, giving Specific Expectations Earth a vivid blue colour. You can observe water above, below, and at In this section, you will Earth’s surface. Water is a component of every living thing, from the select and use measuring smallest bacterium to the largest mammal and the oldest tree. You drink instruments to collect and it, cook with it, wash with it, skate on it, and swim in it. Legends and record data stories involving water have been a part of every culture in human express the results of calcu- history. No other kind of matter is as essential to life as water. lations to the appropriate number of decimal places As refreshing as it may be, water straight from the tap seems rather and significant digits ordinary. Try this: Describe a glass of water to someone who has never select and use appropriate seen or experienced water before. Be as detailed as possible. See how SI units well you can distinguish water from other kinds of matter. communicate your under- standing of the following In addition to water, there are millions of different kinds of matter in the terms: matter, properties, physical property, chemical universe. The dust specks suspended in the air, the air itself, your chair, property, significant digits, this textbook, your pen, your classmates, your teacher, and you — all these accuracy, precision are examples of matter. In the language of science, matter is anything that has mass and volume (takes up space). In the rest of this chapter, you will examine some key concepts related to matter. You have encountered these concepts in previous studies. Before you continue, complete the Checkpoint activity to see what you recall and how well you recall it. As you proceed through this chapter, assess and modify your answers. Describing Matter You must observe matter carefully to describe it well. When describing water, for example, you may have used statements like these: From memory, explain and Water is a liquid. define each of the following concepts. Use descriptions, It has no smell. examples, labelled sketches, Water is clear and colourless. graphic organizers, a computer It changes to ice when it freezes. FAQs file or Help file, or any Water freezes at 0˚C. combination of these. Return to Sugar dissolves in water. your answers frequently during Oil floats on water. this chapter. Modify them as necessary. Characteristics that help you describe and identify matter are called states of matter properties. Figure 1.2 on the next page shows some properties of water properties of matter and hydrogen peroxide. Examples of properties include physical state, physical properties colour, odour, texture, boiling temperature, density, and flammability chemical properties (combustibility). Table 1.2 on the next page lists some common properties physical change of matter. You will have direct experience with most of these properties chemical change during this chemistry course. mixture pure substance element compound Chapter 1 Observing Matter MHR 11  Table 1.2 Common Properties of Matter Physical Properties Chemical Properties Qualitative Quantitative physical state melting point reactivity with water colour boiling point reactivity with air odour density reactivity with pure oxygen crystal shape solubility reactivity with acids malleability electrical conductivity reactivity with pure substances Figure 1.2 Liquid water is ductility thermal conductivity combustibility (flammability) clear, colourless, odourless, and transparent. Hydrogen peroxide hardness toxicity (an antiseptic liquid that many brittleness decomposition people use to clean wounds) has the same properties. It differs Properties may be physical or chemical. A physical property is a property from water, however, in other that you can observe without changing one kind of matter into something properties, such as boiling point, new. For example, iron is a strong metal with a shiny surface. It is solid at density, and reactivity with acids. room temperature, but it can be heated and formed into different shapes. These properties can all be observed without changing iron into some- thing new. A chemical property is a property that you can observe when one kind of matter is converted into a different kind of matter. For example, a chemical property of iron is that it reacts with oxygen to form a different kind of matter: rust. Rust and iron have completely different physical and chemical properties. Figure 1.3 shows another example of a chemical property. Glucose test paper changes colour in the presence of glucose. Thus, a chemical property of glucose test paper is that it changes colour in response to glucose. Similarly, a chemical property of glucose is that it changes the colour of glucose test paper. Recall that some properties of matter, such as colour, and flammabili- ty, are qualitative. You can describe them in words, but you cannot measure them or express them numerically. Other properties, such as density and boiling point, can be measured and expressed numerically. Such properties are quantitative. In Investigation 1-A you will use both qualitative and quantitative properties to examine a familiar item. Figure 1.3 People with diabetes rely on a chemical property to help them monitor the amount of glucose (a simple sugar) in their blood. 12 MHR Unit 1 Matter and Chemical Bonding  S K I L L F O C U S Initiating and Planning Performing and recording Analyzing and interpreting Observing Aluminum Foil You can easily determine the length and width 3. As a group, review the properties you have of a piece of aluminum foil. You can use a ruler recorded. Reflect on the possible methods to measure these values directly. What about its you brainstormed. Decide on one method, thickness? In this investigation, you will design and try it. (If you are stuck, ask your teacher a method for calculating the thickness of for a clue.) aluminum foil. Analysis Problem 1. Consider your value for the thickness of the How can you determine the thickness of a piece aluminum foil. Is it reasonable? Why or why of aluminum foil, in centimetres? not? 2. Compare your value with the values obtained Safety Precautions by other groups. (a) In what ways are the values similar? (b) In what ways are the values different? Conclusion 3. (a) Explain how you decided on the method you used. (b) How much confidence do you have in your method? Explain why you have this level of confidence. (c) How much confidence do you have in the value you calculated? Give reasons to justify your answer. Materials Applications 10 cm × 10 cm square of aluminum foil 4. Pure aluminum has a chemical property in ruler common with copper and iron. It reacts with electronic balance oxygen in air to form a different substance calculator with different properties. This substance is chemical reference handbook called aluminum oxide. Copper has the same chemical property. The substance that results Procedure when copper reacts with oxygen is called a 1. Work together in small groups. Brainstorm patina. Similarly, iron reacts with oxygen to possible methods for calculating the thickness form rust. Do research to compare the proper- of aluminum foil. ties and uses (if any) of aluminum oxide, copper patina, and rust. What technologies 2. Observe and record as many physical are available to prevent their formation? What properties of aluminum foil as you can. technologies make use of their formation? CAUTION Do not use the property of taste. Never taste anything in a laboratory. Chapter 1 Observing Matter MHR 13  Using Measurements to Describe Matter In the investigation, you measured the size and mass of a piece of alu- minum foil. You have probably performed these types of measurement many times before. Measurements are so much a part of your daily life that you can easily take them for granted. The clothes you wear come in different sizes. Much of the food you eat is sold by the gram, kilogram, millilitre, or litre. When you follow a recipe, you measure amounts. The dimensions of paper and coins are made to exact specifications. The value of money is itself a measurement. Measurements such as clothing size, amounts of food, and currency are not standard, however. Clothing sizes in Europe are different from those in North America. European chefs tend to measure liquids and powdered solids by mass, rather than by volume. Currencies, of course, differ widely from country to country. To communicate effectively, scientists rely on a standard system of measurement. As you have learned in previous studies, this system is called the International System of Units (Le système international d’unités, SI ). It allows scientists anywhere in the world to describe matter in the same quantitative language. There are seven base SI units, and many more units that are derived from them. The metre (m), the kilogram (kg), and the second (s) are three of the base SI units. You will learn about two more base units, the mole (mol) and the kelvin (K), later in this book. When you describe matter, you use terms such as mass, volume, and temperature. When you measure matter, you use units such as grams, cubic centimetres, and degrees Celsius. Table 1.3 lists some quantities and units that you will use often in this course. You are familiar with all of them except, perhaps, for the mole and the kelvin. The mole is one of the most important units for describing amounts of matter. You will be intro- duced to the mole in Unit 2. The kelvin is used to measure temperature. You will learn more about the kelvin scale in Unit 5. Consult Appendix E if you would like to review other SI quantities and units. Table 1.3 Important SI Quantities and Their Units Quantity Definition SI units or their derived equivalents Equipment use to measure the quantity mass the amount of kilogram (kg) balance matter in an object gram (g) milligram (mg) length the distance metre (m) ruler between two points centimetre (cm) millimetre (mm) temperature the hotness or coldness kelvin (K) thermometer of a substance degrees Celsius (˚C) volume the amount of space cubic metre (m3) beaker, graduated cylinder, or that an object occupies cubic centimetre (cm3) pipette; may also be calculated litre (L) millilitre (mL) mole the amount of a substance mole (mol) calculated not measured density the mass per unit of kilograms per cubic metre (kg/m3) calculated or measured volume of a substance grams per cubic centimetre (g/cm3) energy the capacity to do joule (J) calculated not measured work (to move matter) 14 MHR Unit 1 Matter and Chemical Bonding Measurement and Uncertainty Before you look more closely at matter, you need to know how much you Give five examples of exact can depend on measurements. How can you recognize when a measure- numbers that you have person- ment is trustworthy? How can you tell if it is only an approximation? For ally experienced today or over example, there are five Great Lakes. Are you sure there are five? Is there the past few days. any uncertainty associated with the value “five” in this case? What about the number of millilitres in 1 L, or the number of seconds in 1 min? Numbers such as these — numbers that you can count or numbers that are true by definition — are called exact numbers. You are certain that there are five Great Lakes (or nine books on the shelf, or ten students in the classroom) because you can count them. Likewise, you are certain that there are 1000 mL in 1 L, and 60 s in 1 min. These relationships are true by definition. Now consider the numbers you used and the calculations you did in Investigation 1-A. They are listed in Figure 1.4. Did you verify these dimensions? The area of the aluminum Are you certain that each side square measured 100 cm2 measured exactly 10 cm? Could (10 cm × 10 cm). it have been 9.9 cm or 10.1 cm? If you used an electronic balance, are you certain that the The mass of the aluminum digital read-out was accurate? square, as measured by an Did the last digit fluctuate at electronic balance, may all? If you used a triple-beam balance, are you certain that you have been about 0.33 g. read the correct value? Could it have been 0.34 g or 0.32 g? What reference did you use to find the density? Did you consult more The density of aluminum than one reference? Suppose is 2.70 g/cm3 at a given that the density was actually temperature. 2.699 g/cm3. Would this make a difference in your calculations? Would this make a difference in the certainty of your answer? The thickness of the Are you certain that this value is fair, given the other values aluminum square, calculated that you worked with? Is it fair to using a calculator, may have have such a precise value, with been about 0.001 222 cm. so many digits, when there are so few digits (just two: the 1 and the 0) in your dimensions of the aluminum square? Figure 1.4 Numbers and calculations from Investigation 1-A Chapter 1 Observing Matter MHR 15  During the investigations in this textbook, you will use equipment such as rulers, balances, graduated cylinders, and thermometers to measure matter. You will calculate values with a calculator or with specially programmed software. How exact can your measurements and calculations be? How exact should they be? Two main factors affect your ability to record and communicate meas- urements and calculations. One factor is the instruments you use. The other factor is your ability to read and interpret what the instruments tell you. Examine Figures 1.5 and 1.6. They will help you understand which digits you can know with certainty, and which digits are uncertain. What is the length measured by ruler A? Is it 4.2 cm, or is it 4.3 cm? You cannot be certain. The 2 of 4.2 is an estimate. The 3 of 4.3 is also an estimate. In both cases, therefore, you are uncertain about the last (farthest right) digit. cm 0 1 2 3 4 5 6 7 8 9 10 11 12 ruler A ruler B Figure 1.5 These two rulers 0 1 2 3 4 5 6 7 8 9 10 11 12 measure the same length of the cm blue square. Ruler A is calibrated into divisions of 1 cm. Ruler B What is the length measured by ruler B? Is it 4.27 cm or 4.28 cm? Again, you is calibrated into divisions cannot be certain. Ruler B lets you make more precise measurements than of 0.1 cm. Which ruler can ruler A. Despite ruler B’s higher precision, however, you must still estimate help you make more precise the last digit. The 7 of 4.27 is an estimate. The 8 of 4.28 is also an estimate. measurements? A B Figure 1.6 These two thermometers measure the same temperature. Thermometer A is calibrated into divisions of 0.1˚C. Thermometer B is calibrated into divisions of 1˚C. Which thermometer lets you make more precise measurements? Which digits in each thermometer reading are you certain about? Which digits are you uncertain about? 16 MHR Unit 1 Matter and Chemical Bonding Significant Digits, Certainty, and Measurements All measurements involve uncertainty. One source of this uncertainty is the measuring device itself. Another source is your ability to perceive and interpret a reading. In fact, you cannot measure anything with complete certainty. The last (farthest right) digit in any measurement is always an estimate. The digits that you record when you measure something are called significant digits. Significant digits include the digits that you are certain about and a final, uncertain digit that you estimate. For example, 4.28 g has three significant digits. The first two digits, the 4 and the 2, are certain. The last digit, the 8, is an estimate. Therefore, it is uncertain. The value 4.3 has two significant digits. The 4 is certain, and the 3 is uncertain. How Can You Tell Which Digits Are Significant? You can identify the number of significant digits in any value. Table 1.4 lists some rules to help you do this. Table 1.4 Rules for Determining Significant Digits Rules Examples 1. All non-zero numbers 7.886 has four significant digits. are significant. 19.4 has three significant digits. 527.266 992 has nine significant digits. 2. All zeros that are located 408 has three significant digits. between two non-zero numbers 25 074 has five significant digits. are significant. 3. Zeros that are located to the 0.0907 has three significant digits. left of a value are not significant. They are the 9, the third 0 to the right, and the 7. The function of the 0.0 at the begining is only to locate the decimal. 0.000 000 000 06 has one significant digit. 4. Zeros that are located to the 22 700 may have three significant digits, right of a value may or may not or it may have five significant digits. be significant. See the box below to find out why. Explaining Three Significant Digits The Great Lakes contain 22 700 km3 of water. Is there exactly that amount of water in the Great Lakes? No, 22 700 km3 is an approximate value. The actual volume could be anywhere from 22 651 km3 to 22 749 km3. You can use scientific notation to rewrite 22 700 km3 as 2.27 × 104 km. This shows that only three digits are significant. (See Appendix E at the back of the book, if you would like to review scientific notation.) Explaining Five Significant Digits What if you were able to measure the volume of water in the Great Lakes? You could verify the value of 22 700 km3. Then all five digits (including the zeros) would be significant. Here again, scientific notation lets you show clearly the five significant digits: 2.2700 × 104 km3. Chapter 1 Observing Matter MHR 17  Practice Problems 1. Write the following quantities in your notebook. Beside each quantity, record the number of significant digits. (a) 24.7 kg (e) 8.930 × 105 km (b) 247.7 mL (f) 2.5 g (c) 247.701 mg (g) 0.0003 mL (d) 0.247 01 L (h) 923.2 g 2. Consider the quantity 2400 g. (a) Assume that you measured this quantity. How many significant digits does it have? (b) Now assume that you have no knowledge of how it was obtained. How many significant digits does it have? Accuracy and Precision In everyday speech, you might use the terms “accuracy” and “precision” to mean the same thing. In science, however, these terms are related to certainty. Each, then, has a specific meaning. Accuracy refers to how close a given quantity is to an accepted or expected value. (See Figure 1.7.) Precision may refer to the exactness of a measurement. For example, ruler B in Figure 1.5 lets you measure length with greater precision than ruler A. Precision may also refer to the close- ness of a series of data points. Data that are very close to one another are said to be precise. Examine Figure 1.8. Notice that a set of data can be precise but not accurate. Figure 1.7 Under standard conditions of temperature and pressure, 5 mL of water has a mass of 5 g. Why does the reading on this balance show a different value? 18 MHR Unit 1 Matter and Chemical Bonding  Student A Student B 7 7 6 6 Mass of water (g) Mass of water (g) 5 5 4 4 3 high precision 3 high precision high accuracy low accuracy 2 2 1 1 1 2 3 4 1 2 3 4 Trial number Trial number A B Figure 1.8 Compare student A’s results with results obtained by student B. Two students conducted four trials each to measure the volumes and masses of 5 mL of water. The graphs in Figure 1.8 show their results. The expected value for the mass of water is 5 g. Student A’s results show high precision and high accuracy. Student B’s results show high precision but low accuracy. In the following Express Lab, you will see how the equipment you use affects the precision of your measurements. ExpressLab Significant Digits You know that the precision of a measuring 2. Determine the mass and volume of a quantity device affects the number of significant digits that of water. (The quantity you use is up to you you should report. In this activity, each group will to decide.) use different glassware and a different balance to 3. From the data you collect, calculate the collect data. density of water. Materials 4. Enter your values for mass, volume, and density in the class table. glassware for measuring volume: for example, graduated cylinders, Erlenmeyer flasks, Analysis pipettes or beakers 1. Examine each group’s data and calculated balance value for density. Note how the number of water significant digits in each value for density compares with the number of significant Procedure digits in the measured quantities. 1. Obtain the glassware and balance assigned to 2. Propose a rule or guideline for properly your group. handling significant digits when you multiply and divide measured quantities. Chapter 1 Observing Matter MHR 19  Calculating with Significant Digits In this course, you will often take measurements and use them to calcu- late other quantities. You must be careful to keep track of which digits in your calculations and results are significant. Why? Your results should not imply more certainty than your measured quantities justify. This is especially important when you use a calculator. Calculators usually report results with far more figures — greater certainty — than your data warrant. Always remember that calculators do not make decisions about certainty. You do. There are three rules for reporting significant digits in calculated answers. These rules are summarized in Table 1.5. Reflect on how they apply to your previous experiences. Then examine the Sample Problems that follow. Table 1.5 Rules for Reporting Significant Digits in Calculations Rule 1: Multiplying and Dividing The value with the fewest number of significant digits, going into the calculation, determines the number of significant digits that you should report in your answer. Rule 2: Adding and Subtracting The value with the fewest number of decimal places, going into the calculation, determines the number of decimal places that you should report in your answer. Rule 3: Rounding To get the appropriate number of significant digits (rule 1) or decimal places (rule 2), you may need to round your answer. If your answer ends in a number that is greater than 5, increase the preceding digit by 1. For example, 2.346 can be rounded to 2.35. If your answer ends with a number that is less than 5, leave the preceding number unchanged. For example, 5.73 can be rounded to 5.7. If your answer ends with 5, increase the preceding number by 1 if it is odd. Leave the preceding number unchanged if it is even. For example, 18.35 can be rounded to 18.4, but 18.25 is rounded to 18.2. Sample Problem Reporting Volume Using Significant Digits Problem A student measured a regularly shaped sample of iron and found it to be 6.78 cm long, 3.906 cm wide, and 11 cm tall. Determine its volume to the correct number of significant digits. What Is Required? You need to calculate the volume of the iron sample. Then you need to write this volume using the correct number of significant digits. Continued... 20 MHR Unit 1 Matter and Chemical Bonding Continued... FROM PAGE 20 What Is Given? You know the three dimensions of the iron sample. Length = 6.78 cm (three significant digits) Width = 3.906 cm (four significant digits) Height = 11 cm (two significant digits) Plan Your Strategy To calculate the volume, use the formula Volume = Length × Width × Height V =l×w×h Find the value with the smallest number of significant digits. Your answer can have only this number of significant digits. Act on Your Strategy V =l×w×h = 6.78 cm × 3.906 cm × 11 cm = 291.309 48 cm3 The value 11 cm has the smallest number of significant digits: two. Thus, your answer can have only two significant digits. In order to have only two significant digits, you need to put your answer into scientific notation. V = 2.9 × 102 cm3 Therefore, the volume is 2.9 × 102 cm3, to two significant digits. Check Your Solution Your answer is in cm3. This is a unit of volume. Your answer has two significant digits. The least number of significant digits in the question is also two. Sample Problem Reporting Mass Using Significant Digits Problem Suppose that you measure the masses of four objects as 12.5 g, 145.67 g, 79.0 g, and 38.438 g. What is the total mass of the objects? What Is Required? You need to calculate the total mass of the objects. What Is Given? You know the mass of each object. Continued... Chapter 1 Observing Matter MHR 21  Continued... FROM PAGE 21 Plan Your Strategy Add the masses together, aligning them at the decimal point. Underline the estimated (farthest right) digit in each value. This is a technique you can use to help you keep track of the number of estimated digits in your final answer. In the question, two values have the fewest decimal places: 12.5 and 79.0. You need to round your answer so that it has only one decimal place. PROBLEM TIP Act on Your Strategy Notice that adding the values 12.5 results in an answer that has 145.67 three decimal places. Using 79.0 the underlining technique + 38.438 mentioned in “Plan Your 275.608 Strategy” helps you count them quickly. Total mass = 275.608 g Therefore, the total mass of the objects is 275.6 g. Check Your Solution Your answer is in grams. This is a unit of mass. Your answer has one decimal place. This is the same as the values in the question with the fewest decimal places. Practice Problems 3. Do the following calculations. Express each answer using the correct number of significant digits. (a) 55.671 g + 45.78 g (b) 1.9 mm + 0.62 mm (c) 87.9478 L − 86.25 L (d) 0.350 mL + 1.70 mL + 1.019 mL (e) 5.841 g × 6.03 g 0.6 kg (f) 15 L 17.51 g (g) 2.2 cm3 Chemistry, Calculations, and Communication Mathematical calculations are an important part of chemistry. You will need your calculation skills to help you investigate many of the topics in this textbook. You will also need calculation skills to communicate your measurements and results clearly when you do activities and investiga- tions. Chemistry, however, is more than measurements and calculations. Chemistry also involves finding and interpreting patterns. This is the focus of the next section. 22 MHR Unit 1 Matter and Chemical Bonding  Chemistry Bulletin Air Canada Flight 143 By multiplying 7682 L by 1.77, Pearson calculated that the airplane had 13 597 kg of fuel on board. He subtracted this value from the total amount of fuel for the trip, 22 300 kg, and found that 8703 kg more fuel was needed. To convert kilograms back into litres, Pearson divided the mass, 8703 kg, by 1.77. The result was 4916 L. The crew added 4916 L of fuel to the airplane’s tanks. This conversion number, 1.77, had been used in the past because the density of jet fuel is 1.77 pounds per litre. Unfortunately, the number that should have been used to convert litres into kilograms was 0.803. The crew should have added 20 088 L of fuel, not 4916 L. Air Canada Flight 143 was en route from First officer Maurice Quintal calculated Montréal to Edmonton on July 23, 1983. The their rate of descent. He determined that they airplane was one of Air Canada’s first Boeing would never make Winnipeg. Pearson turned 767s, and its systems were almost completely north and headed toward Gimli, an abandoned computerized. Air Force base. Gimli’s left runway was being While on the ground in Montréal, Captain used for drag-car and go-kart races. Robert Pearson found that the airplane’s fuel Surrounding the runway were families and processor was malfunctioning. As well, all campers. It was into this situation that Pearson three fuel gauges were not operating. Pearson and Quintal landed the airplane. believed, however, that it was safe to fly the Tires blew upon impact. The airplane skid- airplane using manual fuel measurements. ded down the runway as racers and spectators Partway into the flight, as the airplane scrambled to get out of the way. Flight 143 passed over Red Lake, Ontario, one of two fuel finally came to rest 1200 m later, a mere 30 m pumps in the left wing failed. Soon the other from the dazed onlookers. fuel pump failed and the left engine flamed Miraculously no one was seriously injured. out. Pearson decided to head to the closest As news spread around the world, the airplane major airport, in Winnipeg. He began the became known as “The Gimli Glider.” airplane’s descent. At 8400 m, and more than 160 km from the Winnipeg Airport, the right Making Connections engine also failed. The airplane had run out 1. You read that the airplane should have of fuel. received 20 088 L of fuel. Show how this In Montréal, the ground crew had deter- amount was calculated. mined that the airplane had 7682 L of fuel in 2. Use print or electronic resources to find out its fuel tank. Captain Pearson had calculated that the mass of fuel needed for the trip from what caused the loss of the Mars Climate Montréal to Edmonton was 22 300 kg. Since Orbiter spacecraft in September 1999. How fuel is measured in litres, Pearson asked a is this incident related to the “Gimli Glider” mechanic how to convert litres into kilograms. story? Could a similar incident happen He was told to multiply the amount in litres again? Why or why not? by 1.77. Chapter 1 Observing Matter MHR 23  Section Wrap-up In this section, you learned how to judge the accuracy and precision of your measurement. You learned how to recognize significant digits. You also learned how to give answers to calculations using the correct number of significant digits. In the next section, you will learn about the properties and classifica- tion of matter. Section Review 1 K/U Explain the difference between accuracy and precision in your own words. 2 C What SI or SI-derived unit of measurement would you use to describe: (a) the mass of a person (b) the mass of a mouse (c) the volume of a glass of juice (d) the length of your desk (e) the length of your classroom 3 K/U Record the number of significant digits in each of the following values: (a) 3.545 (b) 308 (c) 0.000876 4 K/U Complete the following calculations and give your answer to the correct number of significant digits. (a) 5.672 g + 92.21 g (b) 32.34 km × 93.1 km (c) 66.0 mL × 0.031 mL (d) 11.2 g ÷ 92 mL 5 I What lab equipment would you use in each situation? Why? (a) You need 2.00 mL of hydrogen peroxide for a chemical reaction. (b) You want approximately 1 L of water to wash your equipment. (c) You are measuring 250 mL of water to heat on a hot plate. (d) You need 10.2 mL of alcohol to make up a solution. 6 I Review the graphs in Figure 1.8. Draw two more graphs to show (a) data that have high accuracy but low precision (b) data that have low accuracy and low precision 24 MHR Unit 1 Matter and Chemical Bonding Classifying Matter and Its Changes 1.3 Matter is constantly changing. Plants grow by converting matter from Section Preview/ the soil and air into matter they can use. Water falls from the sky, evapo- Specific Expectations rates, and condenses again to form liquid water in a never-ending cycle. In this section, you will You can probably suggest many more examples of matter changing. identify chemical sub- Matter changes in response to changes in energy. Adding energy to stances and chemical matter or removing energy from matter results in a change. Figure 1.9 changes in everyday life shows a familiar example of a change involving matter and energy. demonstrate an under- standing of the need to removing energy use chemicals safely in everyday life communicate your under- standing of the following terms: physical changes, chemical changes, mixture, pure substance, element, compound liquid state gas state solid state adding energy Figure 1.9 Like all matter, water can change its state when energy is added or removed. Physical and Chemical Changes in Matter A change of state alters the appearance of matter. The composition of matter remains the same, however, regardless of its state. For example, ice, liquid water, and water vapour are all the same kind of matter: water. Melting and boiling other kinds of matter have the same result. The appearance and some other physical properties change, but the matter retains its identity — its composition. Changes that affect the physical appearance of matter, but not its composition, are physical changes. Figure 1.10 shows a different kind of change involving water. Electrical energy is passed through water, causing it to decompose. Two completely different kinds of matter result from this process: hydrogen gas and oxygen gas. These gases have physical and chemical properties that are different from the properties of water and from each other’s properties. Therefore, decomposing water is a change that affects the composition of water. Changes that alter the composition of matter are called chemical Figure 1.10 An electrical changes. Iron rusting, wood burning, and bread baking are three examples current is used to decompose of chemical changes. water. This process is known You learned about physical and chemical properties earlier in this as electrolysis. chapter. A physical change results in a change of physical properties only. A chemical change results in a change of both physical and chemical properties. Chapter 1 Observing Matter MHR 25  Practice Problems Before adopting the metric 4. Classify each situation as either a physical change or a chemical system, Canadians measured change. Explain your reasoning. temperature in units called Fahrenheit degrees (˚F). Based (a) A rose bush grows from a seed that you have planted and on the Fahrenheit scale, water nourished. boils at 212˚F and freezes at (b) A green coating forms on a copper statue when the statue is 32˚F. A few countries, including the United States, still use exposed to air. the Fahrenheit scale. Without (c) Your sweat evaporates to help balance your body temperature. checking any reference (d) Frost forms on the inside of a freezer. materials, design a method for converting Fahrenheit (e) Salt is added to clear chicken broth. temperatures to Celsius (f) Your body breaks down the food you eat to provide energy for your temperatures, and back again. body’s cells. Show your work, and explain your reasoning. (g) Juice crystals dissolve in water. (h) An ice-cream cone melts on a hot day. Classifying Matter All matter can be classified into two groups: mixtures and pure sub- stances. A mixture is a physical combination of two or more kinds of matter. For example, soil is a mixture of sand, clay, silt, and decom- posed leaves and animal bodies. If you look at soil under a magnifying glass, you can see these different components. Figure 1.11 shows another way to see the components of soil. The components in a mixture can occur in different proportions (relative quantities). Each individual component retains its identity. Mixtures in which the different components are clearly visible are called heterogeneous mixtures. The prefix “hetero-” comes from the Greek word heteros, meaning “different.” Mixtures in which the components are blended together so well that the mixture looks like just one substance are called homogeneous Figure 1.11 To see the mixtures. The prefix “homo- ” comes from the Greek word homos, components of soil, add some meaning “the same.” Saltwater, clean air, and grape juice are common soil to a glass of water. What examples. Homogeneous mixtures are also called solutions. You will property is responsible for investigate solutions in Unit 3. separating the components? A pure substance has a definite composition, which stays the same in response to physical changes. A lump of copper is a pure substance. Water (with nothing dissolved in it) is also a pure substance. Diamond, carbon dioxide, gold, oxygen, and aluminum are pure substances, too. Pure substances are further classified into elements and com- Word LINK pounds. An element is a pure substance that cannot be separated chemically into any simpler substances. Copper, zinc, hydrogen, The word “pure” can be used oxygen, and carbon are examples of elements. to mean different things. In ordinary conversation, you A compound is a pure substance that results when two or more might say that orange juice is elements combine chemically to form a different substance. “pure” if no other materials Compounds can be broken down into elements using chemical process- have been added to it. How is es. For example, carbon dioxide is a compound. It can be separated into this meaning of pure different the elements carbon and oxygen. The Concept Organizer on the next from the scientific meaning in page outlines the classification of matter at a glance. The ThoughtLab the term “pure substance?” reinforces your understanding of properties, mixtures, and separation of substances. 26 MHR Unit 1 Matter and Chemical Bonding  Concept Organizer The Classification System for Matter. Matter anything that has mass and volume Pure Substances found in three physical states: matter that has a definite solid, liquid, gas composition Elements Mixtures matter that cannot be decomposed into simpler physical combinations of matter in which each substances component retains its identity Homogeneous Physical Heterogenous Mixtures Mixtures (Solutions) Chemical Changes (Mechanical Mixtures) components are Changes all components blended so that are visible it looks like a Compounds single substance. matter in which two or more elements are chemically combined ThoughtLab Mixtures, Pure Substances, and Changes You frequently use your knowledge of properties 4. Record a mixture that is made with four of to make and separate mixtures and substances. the chemicals. Then suggest one or more You probably do this most often in the kitchen. techniques that you can use to separate the Even the act of sorting clean laundry, however, four chemicals from one another. Write notes depends on your ability to recognize and make and sketch labelled diagrams to show your use of physical properties. This activity is a techniques. Identify the properties that your “thought experiment.” You will use your under- techniques depend on. standing of properties to mix and separate a variety of chemicals, all on paper. Afterward, Analysis your teacher may ask you to test your ideas, 1. In step 2, what properties of the chemicals did either in the laboratory or at home in the kitchen. you use to determine your combinations? 2. In step 3, what properties did you use to Procedure determine your combinations? 1. Consider the following chemicals: table salt, water, baking soda, sugar, iron filings, sand, Application vegetable oil, milk, and vinegar. Identify each 3. Exchange your four-chemical mixture with chemical as a mixture or a pure substance. a partner. Do not include your notes and 2. Which of these chemicals can you mix diagrams. Challenge your partner to suggest together without producing a chemical techniques to separate the four chemicals. change? In your notebook, record as many Then assess each other’s techniques. What of these physical combinations as you can. modifications, if any, would you make to 3. Which of these chemicals can you mix your original techniques? together to produce a chemical change? Record as many of these chemical combinations as you can. Chapter 1 Observing Matter MHR 27  Section Wrap-up Notice that the classification system for matter, shown in the Concept Organizer, is based mainly on the changes that matter undergoes: physical changes to separate mixtures into elements or compounds chemical changes to convert compounds or elements into different compounds or elements To explain how and why these chemical changes occur, you must look “deeper” into matter. You must look at its composition. This is what you will do in the next chapter. You will see how examining the composition of matter leads to a different classification system: the periodic table. You will also see how the periodic table allows chemists to make predictions about the properties and behaviour of matter. Section Review 1 C Copy Figure 1.9 into your notebook. Add the following labels in the appropriate places: evaporation, condensation, melting, freezing, solid- ifying. Note: Some labels may apply to the same places on the diagram. 2 C You may recall that sublimation is a change of state in which a solid changes directly into a gas. The reverse is also true. Add the label “sublimation” to your diagram for question 1. Include arrows to show the addition or removal of energy. 3 K/U List three mixtures that you use frequently. (a) Explain how you know that each is a mixture. (b) Classify each mixture as either heterogeneous or homogenous. 4 K/U List three pure substances that you use frequently. (a) Explain how you know that each is a pure substance. (b) Try to classify each substance as an element or compound. Explain your reasoning. 5 I You are given a mixture of wood chips, sand, coffee grounds, and water. Design a process to clean the water. 6 MC The water going down your drain and toilet is cleaned and recy- cled. You will learn about water purification processes in Chapter 9. (a) Propose a possible series of steps that you could use to clean the waste water from your home. (b) Will this cleaned water be drinkable? Explain your answer. (c) What further steps may be needed to clean this water? 28 MHR Unit 1 Matter and Chemical Bonding  Review Reflecting on Chapter 1 (b) You add baking soda to vinegar, and the Summarize this chapter in the format of your mixture bubbles and froths. choice. Here are a few ideas to use as guidelines: (c) You use a magnet to locate iron nails that List possible interactions among science, tech- were dropped in a barn filled knee-deep nology, society, and the environment (STSE). with straw. Give examples of physical and chemical (d) Carbon dioxide gas freezes at a temperature properties. of −78˚C. Make a table of common SI units. (e) You recover salt from a solution of saltwater Think about measurement and uncertainty. by heating the solution until all the water When is a number exact? has evaporated. Make up a list of values. Challenge your friends (f) The temperature of a compost pile rises as to identify the number of significant digits in the activity of the bacteria inside the pile each. increases. Review the rules for significant digits when 4. Use the terms “accuracy” and “precision” adding, subtracting, multiplying, and dividing to describe the results on the dart boards numbers. shown below. Assume that the darts represent Explain the difference between accuracy and data and the bulls-eye represents the expected precision. value. Give examples of physical and chemical changes. Into what categories can matter be classified? Reviewing Key Terms For each of the following terms, write a sentence that shows your understanding of its meaning. accuracy chemical changes chemical property chemistry Exp. I Exp. II compound element matter mixture physical changes physical property precision properties pure substance significant digits STSE Exp. III Exp. IV Knowledge/Understanding 1. Identify each property as either physical or chemical. 5. Examine the containers on the next page. (a) Hydrogen gas is extremely flammable. (a) What volume of liquid does each container (b) The boiling point of ethanol is 78.5˚C. contain? Be as accurate and precise as (c) Chlorine gas is pale green in colour. possible in your answers. (d) Sodium metal reacts violently with water. (b) Assume that the liquid in all three containers is water. If the flask and the graduated 2. How can you tell the difference between a cylinder are emptied into the beaker, what physical change and a chemical change? is the total volume of water in the beaker? 3. Name the property that each change depends Report your answer to the correct number on. Then classify the property as either of significant digits. chemical or physical. (c) Which container is the best choice for meas- (a) You separate a mixture of gravel and road uring volume in a laboratory? Explain why. salt by adding water to it. Chapter 1 Observing Matter MHR 29  11. A plumber installs a pipe that has a diameter of 10 cm and a length of 2.4 m. Calculate the volume of water (in cm3) that the pipe will hold. Express your answer to the correct number of significant digits. Note: The formula for the volume of a cylinder is V = πr 2h, where r is the radius and h is the height or length. 12. During an investigation, a student monitors the temperature of water in a beaker. The data from the investigation are shown in the table below. (a) What was the average temperature of the water? Express your answer to the appropri- ate number of significant digits. 6. Make each conversion below. (b) The thermometer that the student used has (a) 10 kg to grams (g)