to influence, sway, or entice with some tempting appeal. Antonym Â». The child tried to allure the stray dog into her yard with a piece of bread. DerivativesÂ» apathy.
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Key Objectives 1.3.1 DESCRIBE how Lavoisier transformed
1.3 Thinking Like a Scientist
1.3.2 IDENTIFY three steps in the scientific
method. 1.3.3 EXPLAIN the role collaboration and communication play in science.
Q: How do you think Alexander Fleming tested his hypothesis? In 1928, Alexander Fleming, a Scottish scientist, noticed that a bacteria he was studying did not grow in the presence of a yellow-green mold. Other scientists had made the same observation, but Fleming was the first to recognize its importance. He assumed that the mold had released a chemical that prevented the growth of the bacteria. That chemical was penicillin, which can kill a wide range of harmful bacteria.
Additional Resources Reading and Study Workbook, Lesson 1.3 Available Online or on Digital Media: • Teaching Resources, Lesson 1.3 Review • Laboratory Manual, Lab 1 • Small-Scale Chemistry Laboratory Manual, Lab 1
Key Questions How did Lavoisier help to transform chemistry? What are the steps in the scientific method? What role do collaboration and communication play in science?
CHEMISTRY Y YOU OU Have students study the photograph and read the text that opens the lesson. Ask What made Fleming different from other scientists who had seen this mold? (Fleming recognized the importance of this discovery. He assumed that the mold had released a chemical that prevented the growth of bacteria.)
An Experimental Approach to Science How did Lavoisier help to transform chemistry? The word chemistry comes from the word alchemy. Long before there were chemists, alchemists were studying matter. Alchemy arose independently in many regions of the world. It was practiced in China and India as early as 400 b.c. In the eighth century, Arabs brought alchemy to Spain, and from there it spread quickly to other parts of Europe. You may have heard that alchemists were concerned with searching for a way to change other metals, such as lead, into gold. Although alchemists did not succeed with this quest, the work they did spurred the development of chemistry. Alchemists developed the tools and techniques for working with chemicals. For example, alchemists developed processes for separating mixtures and purifying chemicals. They designed equipment that is still used today, including beakers, flasks, tongs, funnels, and the mortar and pestle, which is shown in Figure 1.10. What they did not do was provide a logical set of explanations for the changes in matter that they observed. Chemists would accomplish that task many years later.
Activate Prior Knowledge Have students draw a T-chart in their notebooks. In the first column, they should write what they already know about the scientific method. In the second column, they should add the new information they learn as they proceed with the lesson.
National Science Education Standards
Figure 1.10 Mortar and Pestle Pharmacists still use a bowl-shaped mortar and club-shaped pestle to mix drugs for patients. The mortar and pestle in this photograph are made of porcelain, which is a hard material. Infer What may be some other uses of a mortar and pestle?
A-1, A-2, E-2, G-1, G-2, G-3
Focus on ELL 1 CONTENT AND LANGUAGE Preview the vocabulary terms by pronouncing each term and having students repeat it. Allow students time to add the terms to their vocabulary notebooks, with definitions, parts of speech, and examples or sketches. Encourage struggling students to add native language equivalents. 2 FRONTLOAD THE LESSON Have students preview and predict what the lesson is
about by reading the first sentence of each major paragraph and looking at the visual displays. Once the lesson has been read, predictions can be confirmed or denied. 3 COMPREHENSIBLE INPUT Use Figure 1.14 to explain how to read a flowchart, and
provide students with a copy of a flowchart that explains each step of the scientific method. Use the Quick Lab to model the scientific method.
Chapter 1 • Lesson 3
Foundations for Reading BUILD VOCABULARY When discussing the two types of variables, explain that one meaning of manipulate is “to manage or control” and one meaning of respond is “to answer or act in turn.”
Explain Figure 1.11 Antoine Lavoisier This portrait of Antoine Lavoisier and his wife Marie Anne was painted by Jacques Louis David in 1788.
An Experimental Approach to Science MAKE A CONNECTION Students often think that an
experiment is a failure if they do not get the expected or right results. As students perform experiments, help them analyze results that do not fit a hypothesis or vary widely from those of other students. Often, you can identify experimental errors that explain deviation. Also point out that scientists can gain important insights from “failed” experiments.
The Scientific Method What are the steps in the scientific method? Scientists have a powerful tool that they use to produce valuable results. Like all scientists, the biochemist shown in Figure 1.12 is using the scientific method to solve difficult problems. The scientific method is a logical, systematic approach to the solution of a scientific probSteps in the scientific method include lem. making observations, proposing and testing hypotheses, and developing theories.
Explore Class Activity
Making Observations The scientific method is useful for solving many kinds of problems. Suppose you try to turn on a flashlight and you notice that it does not light. When you use your senses to obtain information, you make an observation. An observation can lead to a question: What is wrong with the flashlight?
Figure 1.12 Observing With a Microscope Observation is an essential step in the scientific method.
Introduction to Chemistry 15
How Oxygen Got Its Name
PURPOSE Students make hypotheses based on a set of observations. MATERIALS phenolphthalein, 70% solution of 2-propanol, small artist’s paintbrush, sheets of copy paper or white butcher paper, household glass cleaner containing ammonia ADVANCE PREPARATION Prepare a solution of phenolphthalein in alcohol (250 mg of phenolphthalein in 250 mL of 70% 2-propanol). Use the brush to letter messages on sheets of paper. Try messages such as “CHEM-IS-TRY” and “This is a LABOR-atory, not a lab-ORATORY.” Allow the paper to dry until the messages are invisible. Then post the messages around the room in well-ventilated areas. PROCEDURE At intervals, spray each sheet with the glass cleaner. Ask students to hypothesize why the pink messages appear, disappear after a few minutes, and then reappear when the paper is sprayed again. EXPECTED OUTCOME Students are likely to infer that something in the cleaner caused a reversible change to something on the paper. They may infer that the material in the cleaner is volatile.
The ancient Greeks thought that flammable objects contained the element fire, which George Stahl (1660–1734) named phlogiston. During burning, phlogiston transferred to the air. Phlogiston-rich air, now called nitrogen, did not support burning; objects burned brightly in phlogiston-poor air. Lavoisier measured the mass of metals before and after heating in a closed container. He showed that the mass gained by the metal was lost by the air. Thus, the process of burning involved a gain of matter, not a loss of phlogiston. Lavoisier named the portion of air that supported combustion oxygen.
Answers FIGURE 1.10 Sample answers: to grind herbs,
grains, or other food items; to grind pigments for homemade oil paints or watercolors Introduction to Chemistry
By the 1500s in Europe, there was a shift from alchemy to science. Science flourished in Britain in the 1600s, partly because King Charles II was a supporter of the sciences. With his permission, some scientists formed the Royal Society of London for the Promotion of Natural Knowledge. The scientists met to discuss scientific topics and conduct experiments. The society’s aim was to encourage scientists to base their conclusions about the natural world on experimental evidence, not on philosophical debates. In France, Antoine-Laurent Lavoisier did work in the late 1700s that Lavoisier helped to transwould revolutionize the science of chemistry. form chemistry from a science of observation to the science of measurement that it is today. To make careful measurements, Lavoisier designed a balance that could measure mass to the nearest 0.0005 gram. One of the many things Lavoisier accomplished was to settle a longstanding debate about how materials burn. The accepted explanation was that materials burn because they contain phlogiston, which is released into the air as a material burns. To support this explanation, scientists had to ignore the evidence that metals can gain mass as they burn. By the time Lavoisier did his experiments, he knew that there were two main gases in air—oxygen and nitrogen. Lavoisier was able to show that oxygen is required for a material to burn. Lavoisier’s wife Marie Anne, shown in Figure 1.11, helped with his scientific work. She made drawings of his experiments and translated scientific papers from English.
Figure 1.13 Computer Models This scientist is using a computer to model complex molecules, which are difficult to study with experiments alone.
Explain The Scientific Method USE VISUALS Direct students to Figure 1.14 and
ET KIN IC
See scientific models online.
discuss each step. Then discuss how the steps in the scientific method allow scientists to support theories. Ask students to explain why they think some pathways in the flowchart are cyclic rather than straight. (Cyclic pathways occur where steps may occur more than once, as with the processes of developing hypotheses and conducting experiments to test them.)
Misconception Alert Students may think the steps in the scientific method must be done in a particular order every time. Guide students to understand that the steps may or may not be repeated, depending on the problem.
Extend Connect to
The story of how Augusto and Michaela Odone, on their own, developed an oil that relieved the symptoms of adrenoleukodystrophy (ALD)—an inherited neurological disease afflicting their son— is an excellent example of “ordinary people” applying the scientific method. This story is told in the movie Lorenzo’s Oil. Rent or borrow a copy of the movie. Ask students to take notes as they watch the movie on how the Odones use observations, hypotheses, and experiments to help their son.
Testing Hypotheses If you guess that the batteries in the flashlight are dead, you are making a hypothesis. A hypothesis is a proposed explanation for an observation. You can test your hypothesis by putting new batteries in the flashlight. Replacing the batteries is an experiment, a procedure that is used to test a hypothesis. If the flashlight lights, you can be fairly certain that your hypothesis was true. What if the flashlight does not work after you replace the batteries? A hypothesis is useful only if it accounts for what is actually observed. When experimental data does not fit a hypothesis, the hypothesis must be changed. A new hypothesis might be that the light bulb is burnt out. An experiment to test this new hypothesis is to replace the bulb. When you design experiments, you deal with variables, or factors that can change. The variable that you change during an experiment is the independent variable, also called the manipulated variable. The variable that is observed during the experiment is the dependent variable, also called the responding variable. If you keep other factors that can affect the experiment from changing during the experiment, you can relate any change in the dependent variable to changes in the independent variable. For the results of an experiment to be accepted, the experiment must produce the same result no matter how many times it is repeated, or by whom. This is why scientists are expected to publish a description of their procedures along with their results. Sometimes the experiment a scientist must perform to test a hypothesis is difficult or impossible. For example, atoms and molecules, which are some of the smallest units of matter, cannot be easily seen. In these situations, scientists often turn to models to gain more understanding of a problem. A model is a representation of an object or event. Figure 1.13 shows a scientist working with computer models of complex biological molecules. Chemists may also use models to study chemical reactions and processes.
A hypothesis may be revised based on experimental data.
An experiment can lead to observations that support or disprove a hypothesis.
A theory is tested by more experiments and modiﬁed if necessary.
Figure 1.14 The Scientific Method The steps in the scientific method do not have to occur in the order shown. Compare and Contrast How are a hypothesis and a theory similar? How are they different?
Scientiﬁc Law A scientiﬁc law summarizes the results of many observations and experiments.
Differentiated Instruction L1 STRUGGLING STUDENTS Explain to students that if they make a mistake in the lab, the scientific method allows them to repeat their experiments as many times as needed, as long as they record their work. ELL ENGLISH LANGUAGE LEARNERS Have English learners work with a partner to describe, act out, or illustrate in a drawing the different steps that make up the scientific method. Challenge students to identify how they used each step to solve problems in the past. L3 ADVANCED STUDENTS Have students state the constants, the independent variable, and the dependent variable in the Quick Lab experiment.
Chapter 1 • Lesson 3
Q: What was Alexander Fleming’s hypothesis? How could he test his hypothesis?
Scientific Laws Figure 1.14 shows how scientific experiments can lead to laws as well as theories. A scientific law is a concise statement that summarizes the results of many observations and experiments. In Chapter 14, you will study laws that describe how gases behave. One law describes the relationship between the volume of a gas in a container and its temperature. If all other variables are kept constant, the volume of the gas increases as the temperature increases. The law doesn’t try to explain the relationship it describes. That explanation requires a theory.
Quick Lab OBJECTIVE B By completing this activity, students will
Quick Lab Purpose To test the hypoth-
esis that bubble making can be affected by adding sugar or salt Procedure to a bubble-blowing mixture 1. Label three drinking cups 1, 2, and 3. Measure and add one teaspoon of liquid Materials dish detergent to each cup. r3 plastic drinking cups 2. Use the measuring cup to add twormeasuring cup and spoons thirds cup of water to each drinking cup. rliquid dish detergent Then swirl the cups to form a clear mixture. rwater CAUTION Wipe up any spills immediately rtable sugar so that no one will slip and fall. rtable salt 3. Add a half teaspoon of table sugar to cup 2 and a half teaspoon of table salt to rdrinking straw cup 3. Swirl each cup for one minute.
CHEMISTRY Y YOU OU Fleming’s hypothesis was that mold released a chemical that prevented the growth of bacteria. He could test his hypothesis with other types of bacteria to see if the mold had the same affect on them.
4. Dip the drinking straw into cup 1, remove it, and blow gently into the straw to make the largest bubble you can. Practice making bubbles until you feel you have reasonable control over your bubble production. 5. Repeat Step 4 with the mixtures in cups 2 and 3.
be able to test the hypothesis that bubble making can be affected by adding sugar or salt to the bubble-blowing mixture. PREP TIME 5 minutes CLASS TIME 15 minutes SAFETY Remind students to be careful not to draw any liquid into their mouth through the straw. EXPECTED OUTCOME Students conclude that sugar has no effect on bubble production and that salt prevents bubble production. ANALYZE AND CONCLUDE
1. 2. 3. 4.
Analyze and Conclude 1. Observe Did you observe any differences in your ability to produce bubbles using the mixtures in cup 1 and cup 2? 2. Observe Did you observe any differences in your ability to produce bubbles using the mixtures in cup 1 and cup 3? 3. Draw Conclusions What can you conclude about the effects of table sugar and table salt on your ability to produce bubbles? 4. Design an Experiment Propose another hypothesis related to bubble making. Design an experiment to test your hypothesis.
no Yes; no bubbles formed from the liquid in cup 3. Sugar has no effect on bubble production, but salt stops it completely. Answers might include examining the effect of temperature or dilution of the bubble-making mixture. For example, diluting the mixture can reverse the salt effect.
FOR ENRICHMENT Facilitate a class discussion
about the experiments that students proposed for Question 4. Discuss whether or not the experiments will work. Perform two of the experiments and discuss the results. Emphasize the need to learn from “failed” experiments.
Introduction to Chemistry 17
Focus on ELL 4 LANGUAGE PRODUCTION Have students work in groups of four to complete the lab. Make sure each group has ELLs of varied language proficiencies so that more proficient students can help less proficient ones. Have students work according to their proficiency level. BEGINNING: LOW/HIGH Model this lab and use student volunteers to help with each step. For example, ask one student to label the cups and another student to pour the detergent. INTERMEDIATE: LOW/HIGH Provide a picture for each step of the procedure to
depict what is supposed to be done. Provide a chart for answering questions 1-4. ADVANCED: LOW/HIGH Ask students to compare and contrast the use of salt and
sugar for making bubbles.
Answers FIGURE 1.14 A hypothesis and a theory are both
explanations. A hypothesis is only a proposed explanation; a theory is a well-tested explanation for a broad set of observations. When a hypothesis meets the test of repeated experimentation, it may be become a theory. Introduction to Chemistry
Developing Theories Figure 1.14 shows how the steps of the scientific method fit together. Once a hypothesis meets the test of repeated experimentation, it may be raised to a higher level of ideas. It may become a theory. A theory is a well-tested explanation for a broad set of observations. Some of the theories in chemistry are very useful because they help you form mental pictures of objects or processes that cannot be seen. Other theories allow you to predict the behavior of matter. When scientists say that a theory can never be proved, they are not saying that a theory is unreliable. They are simply leaving open the possibility that a theory may need to be changed at some point in the future to explain new observations or experimental results.
Collaboration and Communication What role do collaboration and communication play in science?
No matter how talented the players on a team may be, one player cannot ensure victory for the team. Individuals must collaborate, or work together, for the good of the team. Think about the volleyball players in Figure 1.15. In volleyball, the person who spikes the ball depends on the person who sets the ball. Unless the ball is set properly, the spiker will have limited success. Many sports recognize the importance of collaboration by keeping track of assists. During a volleyball game, the players also communicate with one another so it is clear who is going to do which task. Strategies that are successful in When scientists collabosports can work in other fields, such as science. rate and communicate with one another, they increase the likelihood of a successful outcome.
Collaboration and Communication CRITICAL THINKING Explain that students can learn about research from news reports, from specialized journals, and from the Internet. The more reliable information people have, the better able they are to effectively address public issues related to science and technology. Stress that students should not avoid reading about science, but they should look for reliable sources and approach the news with a certain amount of healthy skepticism. Ask How can the Internet help people learn about advances in science? (Anyone can access information on the Internet.) Ask What is one disadvantage of getting information from the Internet? (The information is not always reliable.) Note that sites with .gov, .edu, and .org domains are usually the most reliable sources, especially those sites that are maintained by federal and state science agencies, colleges and universities, and professional organizations.
Have students conduct an Internet search on a scientific topic of their choice and print the first page of the results. Demonstrate how to locate information to verify a site’s credibility, such as professional affiliations or expert contributors or authors. Then, have students check each source on their printout and note whether they believe the site to be a reliable or unreliable source of scientific information.
Figure 1.15 Teamwork For a volleyball team to win, the players must work together.
Collaboration Scientists choose to collaborate for different reasons. For example, some research problems are so complex that no one person could have all the knowledge, skills, and resources to solve the problem. It is often necessary to bring together individuals from different disciplines. Each scientist will typically bring different knowledge and, perhaps, a different approach to a problem. Just talking with a scientist from another discipline may provide insights that are helpful. There may be a practical reason for collaboration. For example, an industry may give a university funding for pure research in an area of interest to the industry. Scientists at the university get the equipment and financing required to do the research. In exchange, the scientists provide ideas and expertise. The industry may profit from its investment by marketing applications based on the research. Collaboration isn’t always a smooth process. Conflicts can arise about use of resources, amount of work, who is to receive credit, and when and what to publish. Like the students in Figure 1.16, you will likely work in pairs or on a team in the laboratory. If so, you may face some challenges. However, you can also experience the benefits of a successful collaboration.
Figure 1.16 Lab Partners Working in pairs or in a group can be challenging, but it can also be rewarding. Apply Concepts What steps in the scientific method are these students using?
Have students use the Internet to research examples of successful collaborative projects that involved a multidisciplinary approach to solving a scientific problem. For instance, the series of NASA missions to the moon in the 1970s was a collaborative project. Have students orally report their findings to the class; tell students to be prepared for questions. 18 $IBQUFSt-FTTPO
Check for Understanding What role do collaboration and communication play in science? Assess students’ understanding of the roles of collaboration and communication in science by asking for thumbs-up or thumbs-down gestures in response to the statement I understand the importance of collaboration and communication in science and can explain it. ADJUST INSTRUCTION If students use a thumbs-down response, ask students to identify what aspects of collaboration or communication are unclear. Provide a targeted review of those aspects with students.
Chapter 1 • Lesson 3
14. 15. 16.
Evaluate Figure 1.17 Communication Scientists often get together at professional meetings and workshops to discuss their findings and share ideas.
Informal Assessment Ask students to identify an everyday type of problem that could potentially be solved by the scientific method. Then have them explain how they would use the scientific method to solve that problem. Then have students complete the 1.3 Lesson Check.
Reteach Students may mistakenly infer that a theory grows into a law by constant testing and refinement. Or they may confuse a theory with a hypothesis. A hypothesis differs from a theory in that a hypothesis can be formed on the basis of a single set of observations. It cannot become a theory unless it explains a broad set of observations obtained from repeated experimentation. Remind students that theories can, and do, change as new information becomes available through experimentation.
1.3 Lesso LessonCheck
Review How did Lavoisier revolutionize the science of chemistry? List Name three steps in the scientific method. Explain Why are collaboration and communication important in science?
17. Describe What did alchemists contribute to the development of chemistry? 18. Explain How did Lavoisier’s wife help him to communicate the results of his experiments? 19. Describe What process takes place before an article is published in a scientific journal? 20. Explain Why is it important for scientists to publish a description of their procedures along with the results of their experiments?
21. Infer Why should a hypothesis be developed before experiments take place? 22. Compare What is the difference between a theory and a hypothesis? 23. Classify In Chapter 2, you will learn that matter is neither created nor destroyed in any chemical change. Is this statement a theory or a law? Explain your answer.
CHEMISTRY AS THE CENTRAL SCIENCE 24. Do the steps in the scientific method always need to be followed in order? Explain.
Answers FIGURE 1.16 testing a hypothesis and making
observations Introduction to Chemistry 19
Lesson Check Answers 14. He helped transform chemistry from a science of observation to a science of measurement. 15. Sample answers: making observations, testing hypotheses, and developing theories 16. They help increase the likelihood of a successful outcome. 17. They developed the tools and techniques for working with chemicals. 18. She made drawings of his experiments and translated scientific papers.
19. Articles are reviewed by experts in the author’s field of research. 20. so that other scientists can repeat the experiments and confirm the results 21. It guides the design of the experiments. 22. A theory is a well-tested explanation of a broad set of observations; a hypothesis is a proposed explanation for an observation.
23. A law; it is not an explanation. 24. BIGIDEA Sample answer: No; for example, most experiments do not lead directly to the development of or revision of a theory.
Introduction to Chemistry
Communication The way scientists communicate with each other and with the public has changed over the centuries. In earlier centuries, scientists exchanged ideas through letters. They also formed societies to discuss the latest work of their members. When societies began to publish journals, scientists could use the journals to keep up with new discoveries. Today, many scientists, like those in Figure 1.17, work as a team. They can communicate face to face. They also can exchange ideas with other scientists by e-mail, by phone, and at local and international conferences. Scientists still publish their results in scientific journals, which are the most reliable source of information about new discoveries. Most journals are now published online and are readily accessible. Articles are published only after being reviewed by experts in the author’s field. Reviewers may find errors in experimental design or challenge the author’s conclusions. This review process is good for science because work that is not well founded is usually not published. The Internet is a major source of information. One advantage of the Internet is that anyone can get access to information. One disadvantage is that anyone can post information on the Internet without first having that information reviewed. To judge the reliability of information you find on the Internet, you have to consider the source. This same advice applies to articles in newspapers and magazines or the news you receive from television. If a media outlet has a reporter who specializes in science, chances are better that a report will be accurate.
U IRT A
Small-Scale Lab OBJECTIVE After Aft completing l this activity, students will be able to demonstrate their knowledge of safe laboratory practices. CLASS TIME 40 minutes SKILLS FOCUS Observing, communicating results TEACHING TIPS Students need to read Appendix C to answer the questions in the lab. Use this activity as part of an orientation in which you present your rules for working in the laboratory. Provide a floor plan of the room and have students record the location of safety equipment such as an eyewash fountain or a fire extinguisher. After you discuss the safety rules, have students sign a safety contract. For an example, see the safety contract for the small-scale chemistry labs.
Purpose To demonstrate your knowledge of safe laboratory practices
Procedure While doing the chemistry experiments in this textbook, you will work with equipment similar to the equipment shown in the photograph. Your success, and your safety, will depend on following instructions and using safe laboratory practices. To test your knowledge of these practices, answer the question after each safety symbol. Refer to the safety rules in Appendix C and any instructions provided by your teacher.
ANSWERS TO QUESTIONS
Stand back, notify your teacher, and warn other students.
If you accidentally spill water near electrical equipment, what should you do?
Wash your hands thoroughly with soap and water. Wear safety goggles at all times when working in the lab. Tie back long hair and loose clothing. Never reach across a lit burner. Keep flammable materials away from the flame.
After you clean up your work area, what should you do before leaving the laboratory?
It isn’t always appropriate to dispose of chemicals by flushing them down the drain. Follow your teacher’s instructions for disposal. Tell your teacher and nearby classmates. Dispose of the glass as instructed by your teacher.
Focus on ELL 4 LANGUAGE PRODUCTION Have students work in groups of four to complete the lab. Make sure each group has ELLs of varied language proficiencies so that more proficient students can help less proficient ones. Have students work according to their proficiency level. BEGINNING: LOW/HIGH Provide true or false pictures that represent each question on the safety test. For instance, create a picture of a student pouring a chemical into the sink. Students can circle a “thumbs up” or “thumbs down” to indicate if this is a good or bad idea. INTERMEDIATE: LOW/HIGH Show students how to use the appendix in the
textbook. ADVANCED: LOW/HIGH Have students help students with lower proficiencies with
the written answers and predictions.
Chapter 1 • Small-Scale Lab
The small-scale chemistry experiments in this book are designed to help you teach students important chemical principles, not just process. For most experiments, the procedure is short and simple. In many cases, students are asked to construct a grid, place a small-scale reaction surface over the grid, do the experiment, and record their results in a similar grid. Sometimes the students are told to mark the grid with black X’s. These X’s provide black-and-white backgrounds against which students can observe reaction mixtures.
When should safety goggles be worn?
The YOU’RE THE CHEMIST activities ask students to apply what they learned in the initial experiment. Some of these activities could be used for performance-based assessment. FOR ENRICHMENT Have students look at the safety
rules in Appendix C. Have each student choose five of the rules in Appendix C and make a list of what things could happen if each rule is not followed. Organize students into groups of three and have them share their answers with each other.
What precautions should you take when working near an open flame?
Is it always appropriate to dispose of chemicals by flushing them down the sink?
What should you do if glassware breaks?
Introduction to Chemistry 21
Laboratory Hazard Symbols The four-color diamond pictured on page R50 of the text is a familiar sight in every laboratory stockroom and chemical cabinet. The hazard diamond was originally developed by the National Fire Protection Association (NFPA) in response to federal requirements that information about hazardous materials must be visibly posted and easily accessible to all workers. The diamond is divided into four smaller diamonds: blue, red, yellow, and white. The colors symbolize four areas of safety concern. The blue diamond
provides information on potential dangers to human health. The red diamond provides information on the flammability of the material. Yellow provides information on the reactivity of the substance. Each of these three diamonds is occupied by a number ranging from 0 to 4, with 0 representing the lowest level of danger and 4 the highest. The white diamond is reserved for special hazards. Instead of numbers, the NFPA system uses two symbols in this diamond—W and OX—to indicate hazards of particular
interest to firefighters. The W, often seen with a horizontal line through it, provides information about reactivity with water, and OX indicates that the material is an oxidizer. The official NFPA hazard diamond uses only the W and OX symbols in the white diamond; other versions may have an expanded list that indicates whether a substance is an acid (ACID), a base (ALK), corrosive (COR), or radioactive (universal radioactive warning symbol). Introduction to Chemistry