Reading Chapter One: 1.4

Connecting to Your World Shape-sorter toys fascinate young children. Typically, the children try placing a shape in different holes until they find the right one. They may try to place an incorrect shape in the same hole over and over again. An older child has enough experience to place the correct shape in each hole on the first try. The trial-and-error approach used by young children is one method of problem solving, but it is usually not the best one. In this section, you will learn effective ways to solve problems in chemistry.



Key Concepts

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What is a general approach to solving a problem?
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What are the three steps for solving numeric problems?
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What are the two steps for solving conceptual problems?

Reading Strategy

Identifying Main Idea Details Under the heading Solving Numeric Problems, there are three main ideas presented as subheads. As you read, list two details that support each main idea.

Skills Used in Solving Problems

Problem solving is a skill you use all the time. You are in a supermarket. Do you buy a name brand or the store brand of peanut butter? Do you buy the 1-liter bottle or the 2-liter bottle of a carbonated beverage? Do you choose the express line if there are five customers ahead of you or the non-express line with a single shopper who has lots of items?

When you solve a problem you may have a data table, a graph, or another type of visual to refer to. The shopper in Figure 1.23 is reading the label on a can while trying to decide whether to buy the item. She may need to avoid certain ingredients because of a food allergy. Or she may want to know the amount of Calories per serving.

Figure 1.23 A shopper must make many decisions. Some of those decisions are based on data, like the information on a food label.

The skills you use to solve a word problem in chemistry are not that different from those you use while shopping or cooking or planning a party. Effective problem solving always involves developing a plan and then implementing that plan.

Solving Numeric Problems

Because measurement is such an important part of chemistry, most word problems in chemistry require some math. The techniques used in this book to solve numeric problems are conveniently organized into a three-step, problem-solving approach. This approach has been shown to be very helpful and effective. So we recommend that you follow this approach when working on numeric problems in this textbook. The steps for solving a numeric word problem are analyze, calculate, and evaluate. Figure 1.24 summarizes the three-step process and Sample Problem 1.1 shows how the steps work in a problem.

Figure 1.24 This flowchart summarizes the steps for solving a numeric problem. Predicting In which step do you make a plan for getting from what is known to what is unknown?
Analyze

To solve a word problem, you must first determine where you are starting from (identify what is known) and where you are going (identify the unknown). What is known may be a measurement. Or it may be an equation that shows a relationship between measurements. If you expect the answer (the unknown) to be a number, you need to determine what units the answer should have before you do any calculations.

After you identify the known and the unknown, you need to make a plan for getting from the known to the unknown. Planning is at the heart of successful problem solving. As part of planning, you might draw a diagram that helps you visualize a relationship between the known and the unknown. You might need to use a table or graph to identify data or to identify a relationship between a known quantity and the unknown. You may need to select an equation that you can use to calculate the unknown.
Calculate

If you make an effective plan, doing the calculations is usually the easiest part of the process. For some problems, you will have to convert a measurement from one unit to another. Or you may need to rearrange an equation before you can solve for an unknown. However, you will be taught these math skills as needed. There will also be reminders throughout the textbook to use the Math Handbook in Appendix C.
Evaluate

After you calculate an answer, you should evaluate it. Is the answer reasonable? Does it make sense? If not, reread the word problem. Did you copy the data correctly? Did you choose the right equations? It helps to round off the numbers and make an estimate of the answer. If the answer is much larger or much smaller than your estimate, check your calculations.

Check that your answer has the correct unit and the correct number of significant figures. You may need to use scientific notation in your answer. You will study significant figures and scientific notation in Chapter 3.

1.1 Chemistry

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Because living and nonliving things are made of matter, chemistry affects all aspects of life and most natural events.Hint
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Chemistry can be divided into five traditional areas of study: organic chemistry, inorganic chemistry, biochemistry, analytical chemistry, and physical chemistry.Hint
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Pure research can lead directly to an application, but an application can exist before research is done to explain how it works.Hint
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Chemistry can be useful in explaining the natural world, preparing people for career opportunities, and producing informed citizens.Hint

1.2 Chemistry Far and Wide

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Chemists design materials to fit specific needs. Chemists play an essential role in finding ways to conserve energy, produce energy, and store energy.Hint
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Chemists supply the medicines, materials, and technology that doctors use to treat patients. Chemists help to develop more productive crops and safer, more effective ways to protect crops.Hint
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Chemists help to identify pollutants and prevent pollution.Hint
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To study the universe, chemists gather data from afar and analyze matter that is brought back to Earth.Hint

1.3 Thinking Like a Scientist

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Alchemists developed tools and techniques for working with chemicals.Hint
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Lavoisier helped to transform chemistry from a science of observation to the science of measurement that it is today.Hint
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Steps in the scientific method include making observations, testing hypotheses, and developing theories.Hint
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When scientists collaborate and communicate, they increase the likelihood of a successful outcome.Hint

1.4 Problem Solving in Chemistry

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Effective problem solving always involves developing a plan and then implementing the plan.Hint
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The steps for solving a numeric word problem are analyze, calculate, and evaluate. The steps for solving a conceptual problem are analyze and solve.Hint

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Vocabulary Review

Vocabulary

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analytical chemistry
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applied chemistry
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biochemistry
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biotechnology
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chemistry
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experiment
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hypothesis
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inorganic chemistry
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macroscopic
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matter
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microscopic
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manipulated variable
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observation
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organic chemistry
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physical chemistry
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pollutant
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pure chemistry
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responding variable
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scientific law
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scientific method
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technology
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theory