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Problem-solving questions will ask you to apply your understanding of information presented as part of the question. Questions of this type could require you to: ■ interpret results ■ draw conclusions based on results ■ analyze experimental flaws or logical fallacies in arguments ■ make a prediction based on information pro- vided in the question ■ select the best procedure or method to accom- plish a scientific goal ■ select a diagram that best illustrates a principle ■ apply scientific knowledge to everyday life ■ use the work of renowned scientists to explain everyday global issues Some questions will require you to draw on knowl- edge you have acquired through your daily life and prior schooling. In other questions, all the necessary informa- tion will be included in the passage or graphic provided as part of the question. In either case, reviewing basic sci- ence concepts presented in the following chapters and answering as many practice questions as you can will improve your performance. About half the problems on the GED Science Exam will require you to understand, interpret, or apply infor- mation presented in graphical form. Graphical informa- tion includes diagrams, charts, and graphs. Graphics are a concise and organized way of presenting information. Once you realize that all graphics have some common basic elements, it will not matter whether their informa- tion presented is in the area of biology, chemistry, physics, or Earth science. DIAGRAMS Diagrams can be used to show a sequence of events, a chemical or biological process, the setup of a science experiment, a phenomenon, the relationship between different events or species, and so forth. Here are some examples that you can look up in your science textbooks: ■ diagram of an electrochemical cell (physical science)—process ■ diagram of the phases of cell division (life science)—sequence of events ■ pedigree diagram for color blindness (life science)—relationship between events ■ diagrams showing the oxygen and nitrogen cycle (Earth and space science)—process ■ diagram showing the repulsion of like charges (physical science)—phenomenon ■ diagram illustrating the titration technique (chemistry)—setup of an experiment When you see a diagram, first ask yourself what its purpose is: What is it trying to illustrate? Then look at the different labeled parts of the diagram. What is their function? How are they interrelated? CHARTS All charts are composed of rows (horizontal) and columns (vertical). Entries in a single row of a table usu- ally have something in common, and so do entries in a single column. Two common questions about charts involve reading an entry and finding a trend. Is there a change? Do the numbers increase? Decrease? G RAPHS The most common types of graphs are scatter plots, bar graphs, and pie graphs. Whenever a variable depends continuously on another variable, this dependence can be visually represented in a scatter plot. An example of data that can be represented on a scatter plot is popula- tion growth as a function of time. A scatter plot consists of the horizontal (x) axis, the vertical (y) axis, and col- lected data points for variable y, measured at variable x. A graph often contains a legend, especially if there is more then one data set or more than one variable. A leg- end is a key for interpreting the graph. It lists the symbols used to label a particular data set. Bar graphs are similar to scatter plots. Both have a variable y plotted against a variable x. However, in bar graphs, data is represented by bars, rather than by points. Bar graphs are often used to indicate an amount or level, as opposed to a continuous change. You may have seen bar graphs on your family’s utility bill. Utility companies often plot the amount of energy used by an average con- sumer during different months of the year. Pie graphs are used to show what percent of a total is taken up by different components of that whole. For example, a pie chart could be used to show the percent of science students who major in chemistry, physics, biol- ogy, geology, and astronomy. – ABOUT THE GED SCIENCE EXAM– 210 Test Topics The topics covered on the GED Science Exam are: ■ physical science—35% of the questions ■ life science—45% of the questions ■ Earth and space science—20% of the questions On the GED, physical science includes high school physics and chemistry and covers the structure of atoms, the properties of matter, chemical reactions, con- servation of mass and energy, increase in disorder, the laws of motion, forces, and the interactions of energy and matter. Life science deals with subjects covered in high school biology classes, including cell structure, heredity, bio- logical evolution, behavior, and interdependence of organisms. Earth and space science GED questions will test your knowledge of the Earth and solar system, the geochem- ical cycles, the origin and evolution of the Earth, and the universe. Recent Changes in the GED In accordance with Education Standards set forth by the National Academy of Sciences, the GED Science Test has been modified to include more interdisciplinary ques- tions. These questions also fall into one of the three major categories (physical science, life science, and Earth and space science) but focus on themes common to all sciences. Common themes include the scientific method, the organization of knowledge, applications in technol- ogy and everyday situations, and the development of sci- entific ideas through history. Since 50% of the GED Science questions will be interdisciplinary, a chapter will cover each of the following themes: ■ unifying concepts and processes ■ science as inquiry ■ science and technology ■ science and personal and social perspectives ■ history and nature of science Unifying concepts and processes in science include the organization of scientific knowledge, development of scientific models based on experimental evidence, equi- librium, change, conservation, measurement, and rela- tionship between form and function. Approximately two questions on the GED Science Exam will fall into this category. Science as inquiry questions can require you to sum- marize and interpret experimental results, select relevant information, understand and apply the scientific method, make a prediction or draw a conclusion based on given facts, and evaluate the source of experimental flaws and error. There will be about seven questions of this type on the GED. Science and technology questions require you to understand the function of an instrument, instructions for operating an instrument, technological processes, the elements of technological design, how technology uses scientific knowledge to improve products and processes, and the impact of technology on science, human life, and environment. About three questions of this type will appear on the test. Science and personal and social perspectives ques- tions include questions on human health (nutrition, exercise, disease prevention, genetics), climate, pollution, population growth, natural resources, social impact of natural disasters, human-induced environmental haz- ards, public policy, application of scientific knowledge to everyday situations, and application of scientific knowl- edge to explain global phenomena. These questions are quite common. You can expect to see about nine of them on the GED. History and nature of science questions could include a passage on the development of an idea or the- ory through time, or the work of an important scientist. You could also expect to see general questions about the development of science as a field and its principles. You will probably see about three questions of this type on the GED. The chart on the next page summarizes the approxi- mate breakdown of question types and subjects covered in the questions on the GED Science Exam. – ABOUT THE GED SCIENCE EXAM– 211 GED SCIENCE EXAM 50 QUESTIONS, 80 MINUTES Type: 25 conceptual understanding questions, 25 problem-solving questions Format: 25 short paragraph questions, 25 questions based on a passage or graphic Subject: 45% life science questions, 35% physical science questions, 20% Earth and space science questions Content: 25 fundamental science (life, physical, Earth/space) questions, 25 interdisciplinary questions – ABOUT THE GED SCIENCE EXAM– 212 In addition to the interdisciplinary questions, other recent changes to the GED Science Exam include: ■ increased focus on environmental and health top- ics (recycling, heredity, prevention of disease, pol- lution, and climate) ■ increased focus on science as found in daily life ■ increased number of single-item questions ■ decreased number of questions based on the same passage/graphic Now that you have a better idea of the kind of ques- tions that may appear on the GED Science Exam, you can start reviewing the basic science concepts described in the next chapters. W HETHER THEY ARE chemists, biologists, physicists, or geologists, all scientists seek to organ- ize the knowledge and observations they collect. They look for evidence and develop models to provide explanations for their observations. Scientists depend heavily on measurement and developed devices and instruments for measuring different properties of matter and energy. Scientists also use units to make the quantities they measure understandable to other scientists. Questions that come up in every science are: ■ What causes change? ■ What causes stability? ■ How does something evolve? ■ How does something reach equilibrium? ■ How is form related to function?  Systems, Order, and Organization What happens when an Internet search produces too many results? Clearly, having some results is better than hav- ing none, but having too many can make it difficult to find the necessary information quickly. If scientists didn’t systematically organize and order information, looking for or finding a piece of data or making a comparison CHAPTER Unifying Concepts and Processes THIS CHAPTER will review some of the unifying concepts and processes in science. You will learn the questions and themes that are common to each of the scientific disciplines and how scientists seek to answer those questions. 21 213 would be as difficult as looking for one specific book in a huge library in which the books are randomly shelved. In every science, knowledge is grouped into an orderly manner. In biology, an organism is classified into a domain, kingdom, phylum, class, order, family, genus, and species. Members of the same species are the most similar. All people belong to the same species. People and monkeys belong to the same order. People and fish belong to the same kingdom, and people and plants share the same domain. This is an example of hierarchical classifica- tion—each level is included in the levels above. Each species is part of an order, and each order is part of a kingdom, which is a part of domain. Another example of hierarchical classification is your address in the galaxy. It would include your house num- ber, street, city, state, country, continent, planet, star sys- tem, and galaxy. Here is another example of organization in biology. Each organism is made of cells. Many cells make up a tis- sue. Several tissues make up an organ. Several organs make up an organ system. In chemistry, atoms are sorted by atomic number in the periodic table. Atoms that have similar properties are grouped. Scientists also classify periods of time since Earth’s formation 4.6 billion years ago, based on the major events in those eras. Time on Earth is divided into the following eras: Precambrian, Paleozoic, Mesozoic, and Cenozoic. The eras are further divided into periods, and the periods into epochs.  Evidence, Models, and Explanation Scientists look for evidence. The job of a scientist is to observe and explain the observations using factual evi- dence, and develop models that can predict unobserved behavior. Scientific evidence should: ■ be carefully documented and organized ■ be quantified as much as possible ■ be reproducible by other scientists Scientific explanations should: ■ be consistent with observations and evidence ■ be able to predict unobserved behavior ■ be internally consistent (two statements in the same explanation should not contradict each other) Scientific models should: ■ be consistent with observations ■ be consistent with explanations ■ be able to predict unobserved behavior ■ cover a wide range of observations or behaviors  Equilibrium and Change A favorite pastime of scientists is figuring out why things change and why they stay the same. On one hand, many systems seek to establish equilibrium. In organisms, this equilibrium is called homeostasis. It is the tendency of organisms to maintain a stable inner environment, even when the outside environment changes. When people sweat, they are trying to cool off and maintain their equi- librium temperature. Contrary to a common misconception, equilibrium is not a state of rest at which nothing happens. At chemi- cal equilibrium, reactants continue to form products, and products continue to form reactants. However, the rate of formation of reactants is the same as the rate of formation of products, so that no net change is observed. Equilibria are fragile states, and a little change, a tiny force, is often enough to disturb them. Think of a seesaw in balance. A little puff of wind, and the balance is gone. The same is true of chemical equilibrium—increase the pressure or temperature, and the equilibrium will shift. Your body is pretty good at keeping a steady tempera- ture, but when you get sick, you are thrown off balance; up goes your temperature, and out the window goes your homeostasis. Systems at equilibrium appear to be stable and con- stant. But a small disturbance is often enough to change an equilibrium state. The reason for change in a system is reestablishing equilibrium or reaching a more stable state. – UNIFYING CONCEPTS AND PROCESSES– 214 A change is often a response to a gradient or a differ- ence in a property in two parts of a system. Here are some examples of common gradients and the changes they drive. ■ Difference in temperature—causes heat to flow from hotter object (region) to colder object (region). ■ Difference in pressure—causes liquid (water) or gas (air) to flow from region of high pressure to region of low pressure. ■ Difference in electric potential—causes electrons to flow from high potential to low potential. ■ Difference in concentration—causes matter to flow until concentrations in two regions are equalized.  Measurement An established principle in science is that observations should be quantified as much as possible. This means that rather than reporting that it’s a nice day out, a scien- tist needs to define this statement with numbers. By nice, two different people can mean two different things. Some like hot weather. Some like lots of snow. But giving the specifics on the temperature, humidity, pressure, wind speed and direction, clouds, and rainfall allows everyone to picture exactly what kind of a nice day we are having. For the same reason, a scientist studying the response of dogs to loud noise wouldn’t state that the dog hates it when it’s loud. A scientist would quantify the amount of noise in decibels (units of sound intensity) and carefully note the behavior and actions of the dog in response to the sound, without making judgment about the dog’s deep feelings. Now that you are convinced that quantify- ing observations is a healthy practice in science, you will probably agree that instruments and units are also useful. In the table at the bottom of the page are the most common properties scientists measure and common units these properties are measured in.You don’t need to – UNIFYING CONCEPTS AND PROCESSES– 215 COMMON UNITS OF MEASURE Length or distance meter (about a yard) centimeter (about half an inch) micrometer (about the size of a cell) nanometer (often used for wavelengths of light) angstrom (about the size of an atom) kilometer (about half a mile) light-year (used for astronomical distances) Time second, hour, year, century Volume milliliter (about a teaspoon), liter (about ᎏ 1 4 ᎏ of a gallon) Temperature degree Celsius, degree Fahrenheit, or Kelvin Charge coulomb Electric potential volt Pressure atmosphere, mm of Hg, bar Force newton . EXAM 50 QUESTIONS, 80 MINUTES Type: 25 conceptual understanding questions, 25 problem-solving questions Format: 25 short paragraph questions, 25 questions based on a passage or graphic Subject: 45% . life science questions, 35% physical science questions, 20% Earth and space science questions Content: 25 fundamental science (life, physical, Earth/space) questions, 25 interdisciplinary questions –. EXAM– 210 Test Topics The topics covered on the GED Science Exam are: ■ physical science— 35% of the questions ■ life science— 45% of the questions ■ Earth and space science—20% of the questions On the GED,