1: The Chemical World Textbook PDF

1: THE CHEMICAL WORLD  CHAPTER OVERVIEW 1: The Chemical World 1.1: Sand and Water 1.2: Chemicals Compose Ordinary Things 1.3: The Scientific Method - How Chemists Think 1.4: Analyzing and Interpreting Data 1.5: A Beginning Chemist - How to Succeed 1.6: Hypothesis, Theories, and Laws...

1: THE CHEMICAL WORLD  CHAPTER OVERVIEW 1: The Chemical World 1.1: Sand and Water 1.2: Chemicals Compose Ordinary Things 1.3: The Scientific Method - How Chemists Think 1.4: Analyzing and Interpreting Data 1.5: A Beginning Chemist - How to Succeed 1.6: Hypothesis, Theories, and Laws 1.7: The Scope of Chemistry 1.E: Exercises 1: The Chemical World is shared under a CK-12 license and was authored, remixed, and/or curated by Marisa Alviar-Agnew & Henry Agnew. 1 1.1: Sand and Water 1.1: Sand and Water is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts. 1.1.1 https://chem.libretexts.org/@go/page/396607 1.2: Chemicals Compose Ordinary Things Chemistry is the branch of science dealing with the structure, composition, properties, and the reactive characteristics of matter. Matter is anything that has mass and occupies space. Thus, chemistry is the study of literally everything around us—the liquids that we drink, the gases we breathe, the composition of everything from the plastic case on your phone to the earth beneath your feet. Moreover, chemistry is the study of the transformation of matter. Crude oil is transformed into more useful petroleum products, such as gasoline and kerosene, by the process of refining. Some of these products are further transformed into plastics. Crude metal ores are transformed into metals, that can then be fashioned into everything from foil to automobiles. Potential drugs are identified from natural sources, isolated and then prepared in the laboratory. Their structures are systematically modified to produce the pharmaceuticals that have led to vast advances in modern medicine. Chemistry is at the center of all of these processes; chemists are the people that study the nature of matter and learn to design, predict, and control these chemical transformations. Within the branches of chemistry you will find several apparent subdivisions. Inorganic chemistry, historically, focused on minerals and metals found in the earth, while organic chemistry dealt with carbon-containing compounds that were first identified in living things. Biochemistry is an outgrowth of the application of organic chemistry to biology and relates to the chemical basis for living things. In the later chapters of this text we will explore organic and biochemistry in a bit more detail and you will notice examples of organic compounds scattered throughout the text. Today, the lines between the various fields have blurred significantly and a contemporary chemist is expected to have a broad background in all of these areas. In this chapter, we will discuss some of the properties of matter and how chemists measure those properties. We will introduce some of the vocabulary that is used throughout chemistry and the other physical sciences. Let’s begin with matter. Matter is defined as any substance that has mass. It is important to distinguish here between weight and mass. Weight is the result of the pull of gravity on an object. On the Moon, an object will weigh less than the same object on Earth because the pull of gravity is less on the Moon. The mass of an object, however, is an inherent property of that object and does not change, regardless of location, gravitational pull, or anything else. It is a property that is solely dependent on the quantity of matter within the object. Contemporary theories suggests that matter is composed of atoms. Atoms themselves are constructed from neutrons, protons and electrons, along with an ever-increasing array of other subatomic particles. We will focus on the neutron, a particle having no charge; the proton, which carries a positive charge; and the electron, which has a negative charge. Atoms are incredibly small. To give you an idea of the size of an atom, a single copper penny contains approximately 28,000,000,000,000,000,000,000 atoms (that’s 28 sextillion). Because atoms and subatomic particles are so small, their mass is not readily measured using pounds, ounces, grams or any other scale that we would use on larger objects. Instead, the mass of atoms and subatomic particles is measured using atomic mass units (abbreviated amu). The atomic mass unit is based on a scale that relates the mass of different types of atoms to each other (using the most common form of the element carbon as a standard). The amu scale gives us a convenient means to describe the masses of individual atoms and to do quantitative measurements concerning atoms and their reactions. Within an atom, the neutron and proton both have a mass of one amu; the electron has a much smaller mass (about 0.0005 amu). Figure 1.2.1 : Atoms are incredible small. To give you an idea of the size of an atom, a single copper penny contains approximately 28,000,000,000,000,000,000,000 atoms (that’s 28 sextillion). Atomic theory places the neutron and the proton in the center of the atom in the nucleus. In an atom, the nucleus is very small, very dense, carries a positive charge (from the protons) and contains virtually all of the mass of the atom. Electrons are placed in a diffuse cloud surrounding the nucleus. The electron cloud carries a net negative charge (from the charge on the electrons) and in a neutral atom there are always as many electrons in this cloud as there are protons in the nucleus (the positive charges in the nucleus are balanced by the negative charges of the electrons, making the atom neutral). An atom is characterized by the number of neutrons, protons and electrons that it possesses. Today, we recognize at least 116 different types of atoms, each type having a different number of protons in its nucleus. These different types of atoms are called 1.2.1 https://chem.libretexts.org/@go/page/47442 elements. The neutral element hydrogen (the lightest element) will always have one proton in its nucleus and one electron in the cloud surrounding the nucleus. The element helium will always have two protons in its nucleus. It is the number of protons in the nucleus of an atom that defines the identity of an element. Elements can, however, have differing numbers of neutrons in their nucleus. For example, stable helium nuclei exist that contain one, or two neutrons (but they all have two protons). These different types of helium atoms have different masses (3 or 4 amu) and they are called isotopes. For any given isotope, the sum of the numbers of protons and neutrons in the nucleus is called the mass number. All elements exist as a collection of isotopes, and the mass of an element that we use in chemistry, the atomic mass, is the average of the masses of these isotopes. For helium, there is approximately one isotope of Helium-3 for every one million isotopes of Helium-4, hence the average atomic mass is very close to 4 (4.002602). As different elements were discovered and named, abbreviations of their names were developed to allow for a convenient chemical shorthand. The abbreviation for an element is called its chemical symbol. A chemical symbol consists of one or two letters, and the relationship between the symbol and the name of the element is generally apparent. Thus helium has the chemical symbol He, nitrogen is N, and lithium is Li. Sometimes the symbol is less apparent but is decipherable; magnesium is Mg, strontium is Sr, and manganese is Mn. Symbols for elements that have been known since ancient times, however, are often based on Latin or Greek names and appear somewhat obscure from their modern English names. For example, copper is Cu (from cuprum), silver is Ag (from argentum), gold is Au (from aurum), and iron is Fe (from ferrum). Throughout your study of chemistry, you will routinely use chemical symbols and it is important that you begin the process of learning the names and chemical symbols for the common elements. By the time you complete General Chemistry, you will find that you are adept at naming and identifying virtually all of the 116 known elements. Table 1.2.1 contains a starter list of common elements that you should begin learning now! Table 1.2.1 : Names and Chemical Symbols for Common Elements Element Chemical Symbol Element Chemical Symbol Hydrogen H Phosphorus P Helium He Sulfur S Lithium Li Chlorine Cl Beryllium Be Argon Ar Boron B Potassium K Carbon C Calcium Ca Nitrogen N Iron Fe Oxygen O Copper Cu Fluorine F Zinc Zn Neon Ne Bromine Br Sodium Na Silver Ag Magnesium Mg Iodine I Aluminum Al Gold Au Silicon Si Lead Pb The chemical symbol for an element is often combined with information regarding the number of protons and neutrons in a particular isotope of that atom to give the atomic symbol. To write an atomic symbol, begin with the chemical symbol, then write the atomic number for the element (the number of protons in the nucleus) as a subscript, preceding the chemical symbol. Directly above this, as a superscript, write the mass number for the isotope, that is, the total number of protons and neutrons in the nucleus. Thus, for helium, the atomic number is 2 and there are two neutrons in the nucleus for the most common isotope, making the atomic symbol He. In the definition of the atomic mass unit, the “most common isotope of carbon”, C, is defined as having a 4 2 12 6 mass of exactly 12 amu and the atomic masses of the remaining elements are based on their masses relative to this isotope. Chlorine (chemical symbol Cl) consists of two major isotopes, one with 18 neutrons (the most common, comprising 75.77% of natural chlorine atoms) and one with 20 neutrons (the remaining 24.23%). The atomic number of chlorine is 17 (it has 17 protons in its nucleus), therefore the chemical symbols for the two isotopes are Cl and Cl. 35 17 37 17 1.2.2 https://chem.libretexts.org/@go/page/47442 When data is available regarding the natural abundance of various isotopes of an element, it is simple to calculate the average atomic mass. In the example above, Cl was the most common isotope with an abundance of 75.77% and Cl had an abundance 35 17 37 17 of the remaining 24.23%. To calculate the average mass, first convert the percentages into fractions; that is, simply divide them by 100. Now, chlorine-35 represents a fraction of natural chlorine of 0.7577 and has a mass of 35 (the mass number). Multiplying these, we get (0.7577 × 35) = 26.51. To this, we need to add the fraction representing chlorine-37, or (0.2423 × 37) = 8.965; adding, (26.51 + 8.965) = 35.48, which is the weighted average atomic mass for chlorine. Whenever we do mass calculations involving elements or compounds (combinations of elements), we always need to use average atomic masses. Contributions & Attributions Paul R. Young, Professor of Chemistry, University of Illinois at Chicago, Wiki: AskTheNerd; PRY askthenerd.com - pyoung uic.edu; ChemistryOnline.com 1.2: Chemicals Compose Ordinary Things is shared under a CK-12 license and was authored, remixed, and/or curated by Marisa Alviar-Agnew & Henry Agnew. 1.2.3 https://chem.libretexts.org/@go/page/47442 1.3: The Scientific Method - How Chemists Think  Learning Objectives Identify the components of the scientific method. Scientists search for answers to questions and solutions to problems by using a procedure called the scientific method. This procedure consists of making observations, formulating hypotheses, and designing experiments; which leads to additional observations, hypotheses, and experiments in repeated cycles (Figure 1.3.1). Figure 1.3.1 : The Steps in the Scientific Method. Step 1: Make observations Observations can be qualitative or quantitative. Qualitative observations describe properties or occurrences in ways that do not rely on numbers. Examples of qualitative observations include the following: "the outside air temperature is cooler during the winter season," "table salt is a crystalline solid," "sulfur crystals are yellow," and "dissolving a penny in dilute nitric acid forms a blue solution and a brown gas." Quantitative observations are measurements, which by definition consist of both a number and a unit. Examples of quantitative observations include the following: "the melting point of crystalline sulfur is 115.21° Celsius," and "35.9 grams of table salt—the chemical name of which is sodium chloride—dissolve in 100 grams of water at 20° Celsius." For the question of the dinosaurs’ extinction, the initial observation was quantitative: iridium concentrations in sediments dating to 66 million years ago were 20–160 times higher than normal. Step 2: Formulate a hypothesis After deciding to learn more about an observation or a set of observations, scientists generally begin an investigation by forming a hypothesis, a tentative explanation for the observation(s). The hypothesis may not be correct, but it puts the scientist’s understanding of the system being studied into a form that can be tested. For example, the observation that we experience alternating periods of light and darkness corresponding to observed movements of the sun, moon, clouds, and shadows is consistent with either one of two hypotheses: a. Earth rotates on its axis every 24 hours, alternately exposing one side to the sun. b. The sun revolves around Earth every 24 hours. Suitable experiments can be designed to choose between these two alternatives. For the disappearance of the dinosaurs, the hypothesis was that the impact of a large extraterrestrial object caused their extinction. Unfortunately (or perhaps fortunately), this hypothesis does not lend itself to direct testing by any obvious experiment, but scientists can collect additional data that either support or refute it. Step 3: Design and perform experiments After a hypothesis has been formed, scientists conduct experiments to test its validity. Experiments are systematic observations or measurements, preferably made under controlled conditions—that is—under conditions in which a single variable changes. 1.3.1 https://chem.libretexts.org/@go/page/47444 Step 4: Accept or modify the hypothesis A properly designed and executed experiment enables a scientist to determine whether or not the original hypothesis is valid. If the hypothesis is valid, the scientist can proceed to step 5. In other cases, experiments often demonstrate that the hypothesis is incorrect or that it must be modified and requires further experimentation. Step 5: Development into a law and/or theory More experimental data are then collected and analyzed, at which point a scientist may begin to think that the results are sufficiently reproducible (i.e., dependable) to merit being summarized in a law, a verbal or mathematical description of a phenomenon that allows for general predictions. A law simply states what happens; it does not address the question of why. One example of a law, the law of definite proportions, which was discovered by the French scientist Joseph Proust (1754–1826), states that a chemical substance always contains the same proportions of elements by mass. Thus, sodium chloride (table salt) always contains the same proportion by mass of sodium to chlorine, in this case 39.34% sodium and 60.66% chlorine by mass, and sucrose (table sugar) is always 42.11% carbon, 6.48% hydrogen, and 51.41% oxygen by mass. Whereas a law states only what happens, a theory attempts to explain why nature behaves as it does. Laws are unlikely to change greatly over time unless a major experimental error is discovered. In contrast, a theory, by definition, is incomplete and imperfect, evolving with time to explain new facts as they are discovered. Because scientists can enter the cycle shown in Figure 1.3.1 at any point, the actual application of the scientific method to different topics can take many different forms. For example, a scientist may start with a hypothesis formed by reading about work done by others in the field, rather than by making direct observations.  Example 1.3.1 Classify each statement as a law, a theory, an experiment, a hypothesis, an observation. a. Ice always floats on liquid water. b. Birds evolved from dinosaurs. c. Hot air is less dense than cold air, probably because the components of hot air are moving more rapidly. d. When 10 g of ice were added to 100 mL of water at 25°C, the temperature of the water decreased to 15.5°C after the ice melted. e. The ingredients of Ivory soap were analyzed to see whether it really is 99.44% pure, as advertised. Solution a. This is a general statement of a relationship between the properties of liquid and solid water, so it is a law. b. This is a possible explanation for the origin of birds, so it is a hypothesis. c. This is a statement that tries to explain the relationship between the temperature and the density of air based on fundamental principles, so it is a theory. d. The temperature is measured before and after a change is made in a system, so these are observations. e. This is an analysis designed to test a hypothesis (in this case, the manufacturer’s claim of purity), so it is an experiment.  Exercise 1.3.1 Classify each statement as a law, a theory, an experiment, a hypothesis, a qualitative observation, or a quantitative observation. a. Measured amounts of acid were added to a Rolaids tablet to see whether it really “consumes 47 times its weight in excess stomach acid.” b. Heat always flows from hot objects to cooler ones, not in the opposite direction. c. The universe was formed by a massive explosion that propelled matter into a vacuum. d. Michael Jordan is the greatest pure shooter to ever play professional basketball. e. Limestone is relatively insoluble in water, but dissolves readily in dilute acid with the evolution of a gas. Answer a experiment Answer b 1.3.2 https://chem.libretexts.org/@go/page/47444  law Answer c theory Answer d hypothesis Answer e observation Summary The scientific method is a method of investigation involving experimentation and observation to acquire new knowledge, solve problems, and answer questions. The key steps in the scientific method include the following: Step 1: Make observations. Step 2: Formulate a hypothesis. Step 3: Test the hypothesis through experimentation. Step 4: Accept or modify the hypothesis. Step 5: Develop into a law and/or a theory. Contributions & Attributions Wikipedia 1.3: The Scientific Method - How Chemists Think is shared under a CK-12 license and was authored, remixed, and/or curated by Marisa Alviar- Agnew & Henry Agnew. 1.3.3 https://chem.libretexts.org/@go/page/47444 1.4: Analyzing and Interpreting Data 1.4: Analyzing and Interpreting Data is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts. 1.4.1 https://chem.libretexts.org/@go/page/396609 1.5: A Beginning Chemist - How to Succeed Examples of the practical applications of chemistry are everywhere (Figure 1.5.1). Engineers need to understand the chemical properties of the substances needed to design biologically compatible implants for joint replacements; or to design roads, bridges, buildings, and nuclear reactors that do not collapse because of weakened structural materials such as steel and cement. Archeology and paleontology rely on chemical techniques to date bones and artifacts and identify their origins. Although law is not normally considered a field related to chemistry, forensic scientists use chemical methods to analyze blood, fibers, and other evidence as they investigate crimes. In particular, DNA matching—comparing biological samples of genetic material to see whether they could have come from the same person—has been used to solve many high-profile criminal cases as well as clear innocent people who have been wrongly accused or convicted. Forensics is a rapidly growing area of applied chemistry. In addition, the proliferation of chemical and biochemical innovations in industry is producing rapid growth in the area of patent law. Ultimately, the dispersal of information in all the fields in which chemistry plays a part requires experts who are able to explain complex chemical issues to the public through television, print journalism, the Internet, and popular books. Figure 1.5.1 : Chemistry in Everyday Life. Although most people do not recognize it, chemistry and chemical compounds are crucial ingredients in almost everything we eat, wear, and use. Chemical compounds in everyday life: Vitamin C, graphite, lithium cobalt oxide, caffeine, sodium chloride, water Hopefully at this point you are fully convinced of how important and useful the study of chemistry can be. You may, however, still be wondering exactly what it is that a chemist does. Chemistry is the study of matter and the changes that matter undergoes. In general, chemists are interested in both characteristics that you can test and observe, like a chemical's smell or color, and characteristics that are far too small to see, like what the oxygen you breathe in or the carbon dioxide you breath out looks like under a microscope 1,000 times more powerful than any existing in the world today. Wait a minute… how can a chemist know what oxygen and carbon dioxide look like under a microscope that doesn't even exist? What happened to the scientific method? What happened to relying on observations and careful measurements? In fact, because chemists can't see the underlying structure of different materials, they have to rely on the scientific method even more! Chemists are a lot like detectives. Suppose a detective is trying to solve a murder case—what do they do? Obviously, the detective starts by visiting the site of the crime and looking for evidence. If the murderer has left enough clues behind, the detective can piece together a theory explaining what happened. Even though the detective wasn't at the crime scene when the crime was committed and didn't actually see the murderer kill the victim, with the right evidence, the detective can be pretty sure of how the crime took place. It is the same with chemistry. When chemists go into the laboratory, they collect evidence by making measurements. Once chemists have collected enough clues from the properties that they can observe, they use that evidence to piece together a theory explaining the properties that they cannot observe—the properties that are too small to see. What kinds of properties do chemists actually measure in the laboratory? Well, you can probably guess a few. Imagine that you go to dinner at a friend's house and are served something that you don't recognize, what types of observations might you make to 1.5.1 https://chem.libretexts.org/@go/page/47445 determine exactly what you've been given? You might smell the food. You might note the color of the food. You might try to decide whether the food is a liquid or a solid because if it's a liquid, it's probably soup or a drink. The temperature of the food could be useful if you wanted to know whether or not you had been served ice cream! You could also pick up a small amount of food with your fork and try to figure out how much it weighs—a light dessert might be something like an angel cake, while a heavy dessert is probably a pound cake. The quantity of food you have been given might be a clue too. Finally, you might want to know something about the food's texture—is it hard and granular like sugar cubes, or soft and easy to spread, like butter? Believe it or not, the observations you are likely to make when trying to identify an unknown food are very similar to the observations that a chemist makes when trying to learn about a new material. Chemists rely on smell, color, state (whether it is a solid or liquid or gas), temperature, volume, mass (which is related to weight—as will be discussed in a later section), and texture. There is, however, one property possibly used to learn about a food, but that should definitely not be used to learn about a chemical —taste! In the sections on the Atomic Theory, you will see exactly how measurements of certain properties helped early scientists to develop theories about the chemical structure of matter on a scale much smaller than they could ever hope to see. You will also learn how these theories, in turn, allow us to make predictions about new materials that humankind has not yet created. The video below gives you some important tips on how to study chemistry in this class. With practice, you too can learn to think like a chemist, and you may even enjoy it! How To Study Chemistry Video 1.5.1 : How To Study Chemistry. Contributions & Attributions 1.5: A Beginning Chemist - How to Succeed is shared under a CK-12 license and was authored, remixed, and/or curated by Marisa Alviar-Agnew & Henry Agnew. 1.5.2 https://chem.libretexts.org/@go/page/47445 1.6: Hypothesis, Theories, and Laws  Learning Objectives Describe the difference between hypothesis and theory as scientific terms. Describe the difference between a theory and scientific law. Although many have taken science classes throughout the course of their studies, people often have incorrect or misleading ideas about some of the most important and basic principles in science. Most students have heard of hypotheses, theories, and laws, but what do these terms really mean? Prior to reading this section, consider what you have learned about these terms before. What do these terms mean to you? What do you read that contradicts or supports what you thought? What is a Fact? A fact is a basic statement established by experiment or observation. All facts are true under the specific conditions of the observation. What is a Hypothesis? One of the most common terms used in science classes is a "hypothesis". The word can have many different definitions, depending on the context in which it is being used: An educated guess: a scientific hypothesis provides a suggested solution based on evidence. Prediction: if you have ever carried out a science experiment, you probably made this type of hypothesis when you predicted the outcome of your experiment. Tentative or proposed explanation: hypotheses can be suggestions about why something is observed. In order for it to be scientific, however, a scientist must be able to test the explanation to see if it works and if it is able to correctly predict what will happen in a situation. For example, "if my hypothesis is correct, we should see ___ result when we perform ___ test." A hypothesis is very tentative; it can be easily changed. What is a Theory? The United States National Academy of Sciences describes what a theory is as follows: "Some scientific explanations are so well established that no new evidence is likely to alter them. The explanation becomes a scientific theory. In everyday language a theory means a hunch or speculation. Not so in science. In science, the word theory refers to a comprehensive explanation of an important feature of nature supported by facts gathered over time. Theories also allow scientists to make predictions about as yet unobserved phenomena." "A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experimentation. Such fact-supported theories are not "guesses" but reliable accounts of the real world. The theory of biological evolution is more than "just a theory." It is as factual an explanation of the universe as the atomic theory of matter (stating that everything is made of atoms) or the germ theory of disease (which states that many diseases are caused by germs). Our understanding of gravity is still a work in progress. But the phenomenon of gravity, like evolution, is an accepted fact. Note some key features of theories that are important to understand from this description: Theories are explanations of natural phenomena. They aren't predictions (although we may use theories to make predictions). They are explanations as to why we observe something. Theories aren't likely to change. They have a large amount of support and are able to satisfactorily explain numerous observations. Theories can, indeed, be facts. Theories can change, but it is a long and difficult process. In order for a theory to change, there must be many observations or pieces of evidence that the theory cannot explain. Theories are not guesses. The phrase "just a theory" has no room in science. To be a scientific theory carries a lot of weight; it is not just one person's idea about something Theories aren't likely to change. 1.6.1 https://chem.libretexts.org/@go/page/47443 What is a Law? Scientific laws are similar to scientific theories in that they are principles that can be used to predict the behavior of the natural world. Both scientific laws and scientific theories are typically well-supported by observations and/or experimental evidence. Usually scientific laws refer to rules for how nature will behave under certain conditions, frequently written as an equation. Scientific theories are more overarching explanations of how nature works and why it exhibits certain characteristics. As a comparison, theories explain why we observe what we do and laws describe what happens. For example, around the year 1800, Jacques Charles and other scientists were working with gases to, among other reasons, improve the design of the hot air balloon. These scientists found, after many, many tests, that certain patterns existed in the observations on gas behavior. If the temperature of the gas is increased, the volume of the gas increased. This is known as a natural law. A law is a relationship that exists between variables in a group of data. Laws describe the patterns we see in large amounts of data, but do not describe why the patterns exist. What is a Belief? A belief is a statement that is not scientifically provable. Beliefs may or may not be incorrect; they just are outside the realm of science to explore.  Laws vs. Theories A common misconception is that scientific theories are rudimentary ideas that will eventually graduate into scientific laws when enough data and evidence has accumulated. A theory does not change into a scientific law with the accumulation of new or better evidence. Remember, theories are explanations and laws are patterns we see in large amounts of data, frequently written as an equation. A theory will always remain a theory; a law will always remain a law. What’s the difference between a scien… scien… Video 1.6.1: What’s the difference between a scientific law and theory? Summary A hypothesis is a tentative explanation that can be tested by further investigation. A theory is a well-supported explanation of observations. A scientific law is a statement that summarizes the relationship between variables. An experiment is a controlled method of testing a hypothesis. Contributions & Attributions Marisa Alviar-Agnew (Sacramento City College) Henry Agnew (UC Davis) 1.6: Hypothesis, Theories, and Laws is shared under a CK-12 license and was authored, remixed, and/or curated by Marisa Alviar-Agnew & Henry Agnew. 1.6.2 https://chem.libretexts.org/@go/page/47443 1.7: The Scope of Chemistry  Learning Objectives To recognize the breadth, depth, and scope of chemistry. Define chemistry in relation to other sciences. Identify the main disciplines of chemistry. Chemistry is the study of matter—what it consists of, what its properties are, and how it changes. Matter is anything that has mass and takes up space—that is, anything that is physically real. Some things are easily identified as matter—the screen on which you are reading this book, for example. Others are not so obvious. Because we move so easily through air, we sometimes forget that it, too, is matter. Because of this, chemistry is a science that has its fingers in just about everything. Being able to describe the ingredients in a cake and how they change when the cake is baked, for example, is chemistry! Chemistry is one branch of science. Science is the process by which we learn about the natural universe by observing, testing, and then generating models that explain our observations. Because the physical universe is so vast, there are many different branches of science (Figure 1.7.1). Thus, chemistry is the study of matter, biology is the study of living things, and geology is the study of rocks and the earth. Mathematics is the language of science, and we will use it to communicate some of the ideas of chemistry. Figure 1.7.1 : The Relationships between Some of the Major Branches of Science. Chemistry lies more or less in the middle, which emphasizes its importance to many branches of science. Although we divide science into different fields, there is much overlap among them. For example, some biologists and chemists work in both fields so much that their work is called biochemistry. Similarly, geology and chemistry overlap in the field called geochemistry. Figure 1.7.1 shows how many of the individual fields of science are related. At some level, all of these fields depend on matter because they all involve "stuff"; because of this, chemistry has been called the "central science", linking them all together. There are many other fields of science, in addition to the ones (biology, medicine, etc.) listed here.  Example 1.7.1: Science Fields Which fields of study are branches of science? Explain. a. sculpture b. astronomy 1.7.1 https://chem.libretexts.org/@go/page/47441  Solution a. Sculpture is not considered a science because it is not a study of some aspect of the natural universe. b. Astronomy is the study of stars and planets, which are part of the natural universe. Astronomy is therefore a field of science.  Exercise 1.7.1 Which fields of study are branches of science? a. physiology (the study of the function of an animal’s or a plant’s body) b. geophysics c. agriculture d. politics Answer a: yes Answer b: yes Answer c: yes Answer d: no Areas of Chemistry The study of modern chemistry has many branches, but can generally be broken down into five main disciplines, or areas of study: Physical chemistry: Physical chemistry is the study of macroscopic properties, atomic properties, and phenomena in chemical systems. A physical chemist may study such things as the rates of chemical reactions, the energy transfers that occur in reactions, or the physical structure of materials at the molecular level. Organic chemistry: Organic chemistry is the study of chemicals containing carbon. Carbon is one of the most abundant elements on Earth and is capable of forming a tremendously vast number of chemicals (over twenty million so far). Most of the chemicals found in all living organisms are based on carbon. Inorganic chemistry: Inorganic chemistry is the study of chemicals that, in general, are not primarily based on carbon. Inorganic chemicals are commonly found in rocks and minerals. One current important area of inorganic chemistry deals with the design and properties of materials involved in energy and information technology. Analytical chemistry: Analytical chemistry is the study of the composition of matter. It focuses on separating, identifying, and quantifying chemicals in samples of matter. An analytical chemist may use complex instruments to analyze an unknown material in order to determine its various components. Biochemistry: Biochemistry is the study of chemical processes that occur in living things. Research may cover anything from basic cellular processes up to understanding disease states so that better treatments can be developed. Figure 1.7.2 : (left) Measurement of trace metals using atomic spectroscopy. (right) Measurement of hormone concentrations. In practice, chemical research is often not limited to just one of the five major disciplines. A particular chemist may use biochemistry to isolate a particular chemical found in the human body such as hemoglobin, the oxygen carrying component of red 1.7.2 https://chem.libretexts.org/@go/page/47441 blood cells. He or she may then proceed to analyze the hemoglobin using methods that would pertain to the areas of physical or analytical chemistry. Many chemists specialize in areas that are combinations of the main disciplines, such as bioinorganic chemistry or physical organic chemistry. History of Chemistry The history of chemistry is an interesting and challenging one. Very early chemists were often motivated mainly by the achievement of a specific goal or product. Making perfume or soaps did not need a lot of theory, just a good recipe and careful attention to detail. There was no standard way of naming materials (and no periodic table that we could all agree on). It is often difficult to figure out exactly what a particular person was using. However, the science developed over the centuries by trial and error. Major progress was made toward putting chemistry on a solid foundation when Robert Boyle (1637-1691) began his research in chemistry (Figure 1.7.3). He developed the basic ideas about the behavior of gases. He could then describe gases mathematically. Boyle also helped form the idea that small particles could combine to form molecules. Many years later, John Dalton used these ideas to develop the atomic theory. Figure 1.7.3 : Robert Boyle. The field of chemistry began to develop rapidly in the 1700's. Joseph Priestley (1733-1804) isolated and characterized several gases: oxygen, carbon monoxide, and nitrous oxide. It was later discovered that nitrous oxide ("laughing gas") worked as an anesthetic. This gas was used for that purpose for the first time in 1844 during a tooth extraction. Other gases discovered during that time were chlorine, by C.W. Scheele (1742-1786) and nitrogen, by Antoine Lavoisier (1743-1794). Lavoisier has been considered by many scholars to be the "father of chemistry". Among other accomplishments, he discovered the role of oxygen in combustion and definitively formulated the law of conservation of matter. Chemists continued to discover new compounds in the 1800's. The science also began to develop a more theoretical foundation. John Dalton (1766-1844) put forth his atomic theory in 1807. This idea allowed scientists to think about chemistry in a much more systematic way. Amadeo Avogadro (1776-1856) laid the groundwork for a more quantitative approach to chemistry by calculating the number of particles in a given amount of a gas. A lot of effort was put forth in studying chemical reactions. These efforts led to new materials being produced. Following the invention of the battery by Alessandro Volta (1745-1827), the field of electrochemistry (both theoretical and applications) developed through major contributions by Humphry Davy (1778-1829) and Michael Faraday (1791-1867). Other areas of the discipline also progressed rapidly. It would take a large book to cover developments in chemistry during the twentieth century and up to today. One major area of expansion was in the area of the chemistry of living processes. Research in photosynthesis in plants, the discovery and characterization of enzymes as biochemical catalysts, elucidation of the structures of biomolecules such as insulin and DNA—these efforts gave rise to an explosion of information in the field of biochemistry. The practical aspects of chemistry were not ignored. The work of Volta, Davy, and Faraday eventually led to the development of batteries that provided a source of electricity to power a number of devices (Figure 1.7.4). 1.7.3 https://chem.libretexts.org/@go/page/47441  Figure 1.7.4 : Battery developed by Volta. (CC BY-SA 3.0; (left) GuidoB and (right) Kkkdc). Charles Goodyear (1800-1860) discovered the process of vulcanization, allowing a stable rubber product to be produced for the tires of all the vehicles we have today. Louis Pasteur (1822-1895) pioneered the use of heat sterilization to eliminate unwanted microorganisms in wine and milk. Alfred Nobel (1833-1896) invented dynamite (Figure 1.7.5). After his death, the fortune he made from this product was used to fund the Nobel Prizes in science and the humanities. J.W. Hyatt (1837-1920) developed the first plastic. Leo Baekeland (1863-1944) developed the first synthetic resin, widely used for inexpensive and sturdy dinnerware. Figure 1.7.5 : Dynamite explosion in Panama, Central America (1908). Today, chemistry continues to be essential to the development of new materials and technologies, from semiconductors for electronics to powerful new medicines, and beyond. Summary Chemistry is the study of matter and the changes it undergoes and considers both macroscopic and microscopic information. Matter is anything that has mass and occupies space. The five main disciplines of chemistry are physical chemistry, organic chemistry, inorganic chemistry, analytical chemistry and biochemistry. Many civilizations contributed to the growth of chemistry. A lot of early chemical research focused on practical uses. Basic chemistry theories were developed during the nineteenth century. New materials and batteries are a few of the products of modern chemistry. 1.7: The Scope of Chemistry is shared under a CK-12 license and was authored, remixed, and/or curated by Marisa Alviar-Agnew & Henry Agnew. 1.7.4 https://chem.libretexts.org/@go/page/47441 1.E: Exercises 1.1: Soda Pop Fizz 1.2: Chemicals Compose Ordinary Things 1.3: All Things Are Made of Atoms and Molecules 1.4: The Scientific Method: How Chemists Think Use the following paragraph to answer the first two questions. In 1928, Sir Alexander Fleming was studying Staphylococcus bacteria growing in culture dishes. He noticed that a mold called Penicillium was also growing in some of the dishes. In Figure 1.13, Petri dish A represents a dish containing only Staphylococcus bacteria. The red dots in dish B represent Penicillium colonies. Fleming noticed that a clear area existed around the mold because all the bacteria grown in this area had died. In the culture dishes without the mold, no clear areas were present. Fleming suggested that the mold was producing a chemical that killed the bacteria. He decided to isolate this substance and test it to see if it would kill bacteria. Fleming grew some Penicillium mold in a nutrient broth. After the mold grew in the broth, he removed all the mold from the broth and added the broth to a culture of bacteria. All the bacteria died. 1. Which of the following statements is a reasonable expression of Fleming’s hypothesis? a. Nutrient broth kills bacteria. b. There are clear areas around the Penicillium mold where Staphylococcus doesn't grow. c. Mold kills bacteria. d. Penicillium mold produces a substance that kills Staphylococcus. e. Without mold in the culture dish, there were no clear areas in the bacteria. 2. Fleming grew Penicillium in broth, then removed the Penicillium and poured the broth into culture dishes containing bacteria to see if the broth would kill the bacteria. What step in the scientific method does this represent? a. Collecting and organizing data b. Making a hypothesis c. Testing a hypothesis by experiment d. Rejecting the old hypothesis and making a new one e. None of these A scientific investigation is NOT valid unless every step in the scientific method is present and carried out in the exact order listed in this chapter. a. True b. False Which of the following words is closest to the same meaning as hypothesis? a. fact b. law c. formula d. suggestion e. conclusion Why do scientists sometimes discard theories? a. the steps in the scientific method were not followed in order b. public opinion disagrees with the theory c. the theory is opposed by the church d. contradictory observations are found e. congress voted against it Gary noticed that two plants which his mother planted on the same day, that were the same size when planted, were different in size after three weeks. Since the larger plant was in the full sun all day and the smaller plant was in the shade of a tree most of the day, Gary believed the sunshine was responsible for the difference in the plant sizes. In order to test this, Gary bought ten small plants of the same size and type. He made sure they had the same size and type of pot. He also made sure they had the same amount and 1.E.1 https://chem.libretexts.org/@go/page/52961 type of soil. Then Gary built a frame to hold a canvas roof over five of the plants while the other five were nearby but out in the sun. Gary was careful to make sure that each plant received exactly the same amount of water and plant food every day. 1. Which of the following is a reasonable statement of Gary’s hypothesis? a. Different plants have different characteristics. b. Plants that get more sunshine grow larger than plants that get less sunshine. c. Plants that grow in the shade grow larger. d. Plants that don’t receive water will die. e. Plants that receive the same amount of water and plant food will grow the same amount. 2. What scientific reason might Gary have for insisting that the container size for the all plants be the same? a. Gary wanted to determine if the size of the container would affect the plant growth. b. Gary wanted to make sure the size of the container did not affect differential plant growth in his experiment. c. Gary want to control how much plant food his plants received. d. Gary wanted his garden to look organized. e. There is no possible scientific reason for having the same size containers. 3. What scientific reason might Gary have for insisting that all plants receive the same amount of water everyday? a. Gary wanted to test the effect of shade on plant growth and therefore, he wanted to have no variables other than the amount of sunshine on the plants. b. Gary wanted to test the effect of the amount of water on plant growth. c. Gary's hypothesis was that water quality was affecting plant growth. d. Gary was conserving water. e. There is no possible scientific reason for having the same amount of water for each plant every day. 4. What was the variable being tested in Gary's experiment? a. the amount of water b. the amount of plant food c. the amount of soil d. the amount of sunshine e. the type of soil 5. Which of the following factors may be varying in Gary’s experimental setup that he did not control? a. individual plant variation b. soil temperature due to different colors of containers c. water loss due to evaporation from the soil d. the effect of insects which may attack one set of plants but not the other e. All of the above are possible factors that Gary did not control. When a mosquito sucks blood from its host, it penetrates the skin with its sharp beak and injects an anti-coagulant so the blood will not clot. It then sucks some blood and removes its beak. If the mosquito carries disease-causing microorganisms, it injects these into its host along with the anti-coagulant. It was assumed for a long time that the virus typhus was injected by the louse when sucking blood in a manner similar to the mosquito. But apparently this is not so. The infection is not in the saliva of the louse, but in the feces. The disease is thought to be spread when the louse feces come in contact with scratches or bite wounds in the host's skin. A test of this was carried out in 1922 when two workers fed infected lice on a monkey, taking great care that no louse feces came into contact with the monkey. After two weeks, the monkey had NOT become ill with typhus. The workers then injected the monkey with typhus and it became ill within a few days. Why did the workers inject the monkey with typhus near the end of the experiment? a. to prove that the lice carried the typhus virus b. to prove the monkey was similar to man c. to prove that the monkey was not immune to typhus d. to prove that mosquitoes were not carriers of typhus e. the workers were mean Eijkman fed a group of chickens exclusively on rice whose seed coat had been removed (polished rice or white rice). The chickens all developed polyneuritis (a disease of chickens) and died. He fed another group of chickens unpolished rice (rice that still had its 1.E.2 https://chem.libretexts.org/@go/page/52961 seed coat). Not a single one of them contracted polyneuritis. He then gathered the polishings from rice (the seed coats that had been removed) and fed the polishings to other chickens that were sick with polyneuritis. In a short time, the birds all recovered. Eijkman had accurately traced the cause of polyneuritis to a faulty diet. For the first time in history, a food deficiency disease had been produced and cured experimentally. Which of the following is a reasonable statement of Eijkman’s hypothesis? a. Polyneuritis is a fatal disease for chickens. b. White rice carries a virus for the disease polyneuritis. c. Unpolished rice does not carry the polyneuritis virus. d. The rice seed coat contains a nutrient that provides protection for chickens against polyneuritis. e. None of these is a reasonable statement of Eijkman's hypothesis. The three questions below relate to the following paragraphs. Scientist A noticed that in a certain forest area, the only animals inhabiting the region were giraffes. He also noticed that the only food available for the animals was on fairly tall trees and as the summer progressed, the animals ate the leaves high and higher on the trees. The scientist suggested that these animals were originally like all other animals but generations of animals stretching their necks to reach higher up the trees for food, caused the species to grow very long necks. Scientist B conducted experiments and observed that stretching muscles does NOT cause bones to grow longer nor change the DNA of animals so that longer muscles would be passed on to the next generation. Scientist B, therefore, discarded Scientist A's suggested answer as to why all the animals living in the area had long necks. Scientist B suggested instead that originally many different types of animals including giraffes had lived in the region but only the giraffes could survive when the only food was high in the trees, and so all the other species had left the area. 1. Which of the following statements is an interpretation, rather than an observation? A. The only animals living in the area were giraffes. B. The only available food was on tall trees. C. Animals which constantly stretch their necks will grow longer necks. D. A, B, and C are all interpretations. E. A, B, and C are all observations. 2. Scientist A's hypothesis was that A. the only animals living in the area were giraffes. B. the only available food was on tall trees. C. animals which constantly stretch their necks will grow longer necks. D. the animals which possess the best characteristics for living in an area, will be the predominant species. E. None of the above are reasonable statements of Scientist A's hypothesis. 3. Scientist A's hypothesis being discarded is A. evidence that the scientific method doesn’t always work. B. a result achieved without use of the scientific method. C. an example of what happened before the scientific method was invented. D. an example of the normal functioning of the scientific method. E. an unusual case. When a theory has been known for a long time, it becomes a law. a. True b. False During Pasteur's time, anthrax was a widespread and disastrous disease for livestock. Many people whose livelihood was raising livestock lost large portions of their herds to this disease. Around 1876, a horse doctor in eastern France named Louvrier, claimed to have invented a cure for anthrax. The influential men of the community supported Louvrier's claim to have cured hundreds of cows of anthrax. Pasteur went to Louvrier's hometown to evaluate the cure. The cure was explained to Pasteur as a multi-step process during which: 1) the cow was rubbed vigorously to make her as hot as possible; 2) long gashes were cut into the cows skin and turpentine was poured into the cuts; 3) an inch-thick coating of cow manure mixed with hot vinegar was plastered onto the cow and the cow was completely wrapped in a cloth. Since some cows recover from anthrax with no treatment, performing the cure on a single cow would not be conclusive, so Pasteur proposed an experiment to test Louvrier's cure. Four healthy cows were to be 1.E.3 https://chem.libretexts.org/@go/page/52961 injected with anthrax microbes, and after the cows became ill, Louvrier would pick two of the cows (A and B) and perform his cure on them while the other two cows (C and D) would be left untreated. The experiment was performed and after a few days, one of the untreated cows died and one of them got better. Of the cows treated by Louvrier's cure, one cow died and one got better. In this experiment, what was the purpose of infecting cows C and D? a. So that Louvrier would have more than two cows to choose from. b. To make sure the injection actually contained anthrax. c. To serve as experimental controls (a comparison of treated to untreated cows). d. To kill as many cows as possible. A hypothesis is a. a description of a consistent pattern in observations. b. an observation that remains constant. c. a theory that has been proven. d. a tentative explanation for a phenomenon. A number of people became ill after eating oysters in a restaurant. Which of the following statements is a hypothesis about this occurrence? a. Everyone who ate oysters got sick. b. People got sick whether the oysters they ate were raw or cooked. c. Symptoms included nausea and dizziness. d. The cook felt really bad about it. e. Bacteria in the oysters may have caused the illness. Which statement best describes the reason for using experimental controls? a. Experimental controls eliminate the need for large sample sizes. b. Experimental controls eliminate the need for statistical tests. c. Experimental controls reduce the number of measurements needed. d. Experimental controls allow comparison between groups that are different in only one independent variable. A student decides to set up an experiment to determine the relationship between the growth rate of plants and the presence of detergent in the soil. He sets up 10 seed pots. In five of the seed pots, he mixes a precise amount of detergent with the soil and the other five seed pots have no detergent in the soil. The five seed pots with detergent are placed in the sun and the five seed pots with no detergent are placed in the shade. All 10 seed pots receive the same amount of water and the same number and type of seeds. He grows the plants for two months and charts the growth every two days. What is wrong with his experiment? a. The student has too few pots. b. The student has two independent variables. c. The student has two dependent variables. d. The student has no experimental control on the soil. A scientist plants two rows of corn for experimentation. She puts fertilizer on row 1 but does not put fertilizer on row 2. Both rows receive the same amount of sun and water. She checks the growth of the corn over the course of five months. What is acting as the control in this experiment? a. Corn without fertilizer. b. Corn with fertilizer. c. Amount of water. d. Height of corn plants. If you have a control group for your experiment, which of the following is true? a. There can be more than one difference between the control group and the test group, but not more three differences, or else the experiment is invalid. b. The control group and the test group may have many differences between them. c. The control group must be identical to the test group except for one variable. d. None of these are true. 1.E.4 https://chem.libretexts.org/@go/page/52961 If the hypothesis is rejected by the experiment, then: a. the experiment may have been a success. b. the experiment was a failure. c. the experiment was poorly designed. d. the experiment didn't follow the scientific method. A well-substantiated explanation of an aspect of the natural world is a: a. theory. b. law. c. hypothesis. d. None of these. 1.5: A Beginning Chemist: How to Succeed 1.E: Exercises is shared under a CK-12 license and was authored, remixed, and/or curated by Marisa Alviar-Agnew & Henry Agnew. 1.E.5 https://chem.libretexts.org/@go/page/52961