Chapter 1: Chemistry: an Introduction 1

Chapter 1: Chemistry: An Introduction 1

CHAPTER 1

Chemistry: An Introduction

Introduction

Your study of chemistry will require work on your part. Use all of the resources available to you so that you can get the most out of the effort you put into learning chemistry. The textbook should be your primary resource, but do not hesitate to turn to this Study Guide for additional help.

This chapter introduces you to how scientists solve problems. Learning how to solve problems is an important part of any chemistry course. Problem solving means more than just calculating a numerical answer. It also includes sifting through the given information, deciding which pieces of information are useful, and finally selecting an approach that will solve the problem. The problem-solving skills you develop can be useful to you throughout your life.

Studying Chemistry

What does it mean to “know chemistry”? And what makes chemistry courses among the most difficult courses you take? We have asked these questions of students at the University of Illinois at the beginning of the academic year for the past several years, and while not all of the answers are the same, the spirit of the answers is quite consistent. According to many of the students, “knowing chemistry” essentially means knowing “a bunch of stuff.” Generally this “stuff” is said to consist of unrelated, and often counterintuitive, facts, equations, and constants. “Knowing chemistry” also means solving problems. These problems are usually math based and are solved by plugging the right numbers into the right equations. These understandings (or rather misunderstandings) of chemistry may help to explain some of the difficulty with chemistry courses. It is a hard task to memorize a great deal of disparate facts, especially when they seem to go against our original ideas.

So what can be done about this? Can studying chemistry be made more enjoyable? Yes. However, the way of doing this may seem ironic, at least initially. One of the reasons that chemistry is so difficult is because of the way students try to make it easier. What does this mean? Read this passage and see to what extent it sounds like you:

You attend all the lectures and studiously take notes on everything the professor writes on the board. You become distracted when the professor seems to go on a tangent or derives an equation or proves a point. You dislike it when the professor follows a line of thought that proves to be incorrect just to make a point. You rarely ask questions either of the professor or of yourself during the lecture. You also view others’ questions during the lectures as diversions.

You generally do all of the assigned homework questions. You usually go straight to the problems and try to do them with minimal reading of the text. This usually consists of trying a problem, and, if you have difficulty, going to a section in the chapter looking for an example problem. When you do read the text, you generally pay little attention to the graphs and figures and rarely write questions about what you have read. Sometimes you do the problems with the Solutions Manual open, but you take only a small peek because once you see how to set up the problem you can usually solve it. You can answer most of the “what” questions, but have difficulty with the “why” questions. You have become adept at using units to solve problems you really do not understand.

Obviously this does not apply to you exactly, but how many of these characteristics come close to describing you? While no one student is exactly like the student described, all of the students we have talked with have some of these characteristics. And this is not to say that these ideas are completely unreasonable; in fact, many of the qualities are admirable. For example, the described student goes to all the lectures and does all the homework. In fact, some students as described above do well in their chemistry courses. So what is the problem?

While some of the students like the one described are successful in their chemistry courses, success often comes with much unnecessary frustration. Worse yet, many of the students described have so much difficulty they either drop the course or end up doing quite poorly. Many of the latter students spend more and more time studying while getting less and less out of it.

What is most ironic about this is there is a cyclical pattern that we have seen for good, hardworking students who end up doing poorly. They see chemistry as unrelated facts, and so they study for it that way. They expect the material to be counterintuitive, so it is. They do not think of chemistry as being about concepts, so it is not. By using shortcuts, mnemonic devices, and memorized algorithms, they actually make chemistry more difficult because when they come across a problem they have not seen before (which occurs in chemistry courses), they have no idea what to do with it. They are not used to trial and error and are unfamiliar with the idea of making mistakes as a way of learning. Thus they learn less. The more difficult the material becomes, the more they study (assuming they do not give up). But they do not know how to study more effectively.

When you understand chemistry, you can solve unique problems by applying fundamental ideas, not by using memorized solutions or plugging numbers into an equation. You should also understand the following:

1.Chemistry content should make sense. Many of our students have stated that when answering a question they think about what makes sense and then say the opposite. Because, after all, this is chemistry, and “the answer is always the opposite of what you think it should be.” While the students say this somewhat in jest, many actually believe it to some extent. One of the goals of learning chemistry is to be able to understand, explain, and predict real phenomena in the real world. You should strive for an understanding of the connectedness of the ideas; you should not just memorize equations and methods for solving problems. The ideas and concepts support each other and are consistent. Make sure to understand it this way.

2.Explaining is different from knowing or remembering, and formulas and equations are not explanatory devices. For example, claiming “elements want to have an electron configuration like noble gases” may help you figure out that oxygen has a 2− charge as an ion, but it does not explain why. Remembering the equation PV = nRT does not mean you have a good understanding of the gas laws.

3.Scientists use models to try to better understand and explain concepts and ideas. These models are not reality but a way of simplifying our ideas. What you need to do is to understand the models–do not merely memorize the premises of a model, but understand the significance and limitations of the model. Albert Einstein once said “Explanations should be as simple as possible, but not simpler.” This is a good way of thinking about models–we want to maximize understanding and minimize complexity. Science is about making observations and using these to derive models that are further refined by new observations. The observations we make and the questions we want to answer guide our development of the model. For example, when discussing gas laws we generally think of gases as consisting of indestructible particles–no protons, electrons, or neutrons are in this model. Is this wrong? Yes and no. While atoms do consist of subatomic particles, these particles do not serve to increase our understanding of gas laws. Thinking of gases this way does not mean we are saying there are no subatomic particles, only that the model disregards them. A question that always comes up is, “If this model is not the absolute truth, why do we bother studying it at all?” But this is what science is about. Unfortunately, we must develop simplified models because we simply cannot understand reality all at once. Models only become more complicated when we try to answer more questions. Our goal is to keep the model as simple as possible and answer as many questions as possible. When we find ourselves with too many questions we cannot answer, the model is refined and expanded or even disregarded. And it is acceptable that the model is not the “absolute truth” as long as you know this is the case and that you have an understanding of the limitations. Thus understanding the kinetic molecular theory, for example, goes beyond memorizing its premises; you should understand the premises, why they make sense, how they are simplified, what their limitations are, and their significance.

A question you are probably asking yourself at this point is, “What can I do to help myself do well in my chemistry course?” The quick answer is easy–you need to understand chemistry. But how do you do that?

To understand chemistry, you need to take an active role in your own learning. You have undoubtedly heard countless times from your parents and teachers that you are responsible for your own learning. But what does this mean in practice? You already go to class, do your homework, and study for quizzes and exams. What else can you do to take responsibility? One of the best ways to do this is to constantly ask questions. This includes while you are reading a text, attending a lecture, doing homework problems, reviewing your notes, or studying with friends. The key is that you consistently ask “Why?” and “What does this mean?” and “What are the implications?”

For example, when you are in lecture, listen intently to the proofs and derivations. Understand where the knowledge comes from and its implications and limits. Ask questions of the professor or at the very least write questions to yourself during lecture. You can think about these and ask the professor, a teaching assistant, or friends later.

When reading your text, do not read it as a novel. Be critical. Write down questions, look at the graphs and figures, and understand what they are telling you. You have heard the phrase “a picture is worth a thousand words,” and this is true about graphs and figures. There is a lot of information in them, and you should extract and understand as much of it as possible. One goal of a text is to provide a source of detailed information and to slowly develop ideas. You are doing a disservice to yourself if you do not read it thoroughly and repeatedly, and you make learning chemistry more difficult.

In doing homework, use the Solutions Manual sparingly because the crucial part of the problems is setting them up. Many students view “doing problems” as getting them over with more than learning from them. Getting a correct answer does not necessarily imply understanding. Chemistry problems are not meant to be answered quickly and easily, but often require a lot of thought and trial and error. Think about what the problem is asking. Draw a picture. Do not just go directly to an equation, but think about what you have and where you are trying to go. Do not be afraid to make a mistake or to go down an incorrect pathway. Many times you will learn from this. Obviously you have a limited amount of time, and you cannot spend an inordinate amount of time on each problem. But students find that something interesting happens when they do problems this way. The problems seem to get easier, and the students find they can actually do fewer problems with more understanding.

Learning Review

1.Explain why chemistry is important to you even if your career is far removed from the sciences.

2.Aside from helping you to get a good grade in chemistry, of what use are the problem-solving skills you will learn?

3.Imagine that you are a scientist exploring life on the newly discovered planet, Cryon. Cryon is cold and is perpetually covered with snow on one side. While exploring the snowy side of Cryon you repeatedly observe that all the birds have white feathers. You hypothesize that all the birds on Cryon have white feathers. Being a good scientist, you:

a.Declare that all birds on Cryon must be white since all the ones on the snowy side are white.

b.Test your hypothesis about all birds on Cryon being white by observing a bird color on the non-snow-covered part of the planet as well as the snowy side.

c.Elevate your hypothesis about white birds to a natural law that states that all life forms on cold planets that are covered with snow on one side are white.

Answers to Learning Review

1.Chemistry will have a different impact on the career of each individual, but even if your career is far removed from the sciences, chemistry plays an important role in each of our everyday lives. We depend on the science of chemistry to provide us with a better standard of living.

2.Problem-solving skills can be used throughout your life. Many situations require you to think logically, to propose hypothetical solutions, and to choose the most reasonable one. Chemistry can help develop logical thinking skills.

3.You as the scientist in this problem have made some observations. But your information is not complete. You have no information about the color of birds on the other side of Cryon. A good scientist would test the hypothesis about bird color by collecting more data. It would not be appropriate to elevate the hypothesis to a natural law until the hypothesis was more thoroughly tested. Choice c is not correct, so the correct answer is b.