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L_0747 | technology | T_3763 | Figure 2.13 shows the steps of the technological design process. Consider the problem of developing a solar- powered car. Many questions would have to be researched in the design process. For example, what is the best shape for gathering the suns rays? How will the energy from the sun be stored? Will a back-up energy source be needed? After researching the answers, possible designs are developed. This takes imagination as well as reason. Then a model is made of the best design, and the model is tested. This allows any problems with the design to be worked out before a final design is selected. | text | null |
L_0747 | technology | T_3764 | Technological design always has constraints. Constraints are limits on the design. Common constraints include: laws of nature, such as the law of gravity. properties of the materials used. cost of producing a technology. Ethical concerns are also constraints on many technological designs. Like scientists, engineers must follow ethical rules. For example, the technologies they design must be as safe as possible for people and the environment. Engineers must weigh the benefits and risks of new technologies, and the benefits should outweigh the risks. | text | null |
L_0747 | technology | T_3765 | Technology advances as new materials and processes are invented. Computers are a good example. Table 2.5 and the videos below show some of the milestones in their evolution. The evolution of modern computers began in the 1930s. Computers are still evolving today. How have computers changed during your lifetime? (4:11) MEDIA Click image to the left or use the URL below. URL: (5:36) MEDIA Click image to the left or use the URL below. URL: Computer (Year) ENIAC (1946) US Army Photo ERMA (1955) Description Like other early computers, the huge ENIAC computer used vacuum tubes for electrical signals. This made it very large and expensive. It could do just one task at a time. It had to be rewired to change programs. Thats what the women in this photo are doing. The ERMA computer represented a new computer technology. It used transistors instead of vacuum tubes. This allowed computers to be smaller, cheaper, and more energy efficient. Computer (Year) PDP-8 (1968) Description By the late 1960s, tiny transistors on silicon chips were invented. They increased the speed and efficiency of computers. They also allowed computers to be much smaller. The PDP-8 computer pictured here was the first "mini" computer. Macintosh 128K (1984) The next major advance in computers was the develop- ment of microprocessors. A microprocessor consisted of thousands of integrated circuits placed on a tiny sili- con chip. This allowed computers to be more powerful and even smaller. The computer pictured here is the first Macintosh personal computer. MacBook Air (2010) The computers of the 21st century are tiny compared with the lumbering giants of the mid-1900s. Their problem-solving abilities are also immense compared with early computers. The diversity of software pro- grams available today allows users to undertake an immense variety of tasks and no rewiring is needed! | text | null |
L_0747 | technology | T_3766 | Technology is sometimes referred to as applied science, but it has a different goal than science. The goal of science is to increase knowledge. The goal of technology is to use knowledge for practical purposes. Although they have different goals, technology and science work hand in hand. Each helps the other advance. Scientific knowledge is needed to create new technologies. New technologies are used to further science. The microscope is a good example. Scientific knowledge of light allowed 17th century lens makers to make the first microscopes. This new technology let scientists view a world of tiny objects they had never before seen. Figure | text | null |
L_0747 | technology | T_3767 | Whats 100,000 times thinner than a strand of hair? A nanometer. Discover the nanotech boom in Berkeley, where researchers are working to unlock the potential of nanoscience to battle global warming and disease. For more information on nanotechnology, see http://science.kqed.org/quest/video/nanotechnology-takes-off/ . MEDIA Click image to the left or use the URL below. URL: | text | null |
L_0747 | technology | T_3768 | The goal of technology is to solve peoples problems. Therefore, the problems of society generally set the direction that technology takes. Technology, in turn, affects society. It may make peoples lives easier or healthier. Two examples are described in Figure 2.15. You can read about other examples at these URLs: http://mezocore.wordpress.com/ | text | null |
L_0747 | technology | T_3769 | Everyday, women living in the refugee camps of Darfur, Sudan must walk for up to seven hours outside the safety of the camps to collect firewood for cooking, putting them at risk for violent attacks. Now, researchers at Lawrence Berkeley National Laboratory have engineered a more efficient wood-burning stove, which is greatly reducing both the womens need for firewood and the threats against them. For more information on these stoves, see http://scien MEDIA Click image to the left or use the URL below. URL: | text | null |
L_0770 | behavior of gases | T_3945 | Pressure is defined as the amount of force pushing against a given area. How much pressure a gas exerts depends on the amount of gas. The more gas particles there are, the greater the pressure. You usually cannot feel it, but air has pressure. The gases in Earths atmosphere exert pressure against everything they contact. The atmosphere rises high above Earths surface. It contains a huge number of individual gas particles. As a result, the pressure of the tower of air above a given spot on Earths surface is substantial. If you were standing at sea level, the amount of force would be equal to 10.14 newtons per square centimeter (14.7 pounds per square inch). This is illustrated in Figure 4.11. | text | null |
L_0770 | behavior of gases | T_3946 | For a given amount of gas, scientists have discovered that the pressure, volume, and temperature of a gas are related in certain ways. Because these relationships always hold in nature, they are called laws. The laws are named for the scientists that discovered them. | text | null |
L_0770 | behavior of gases | T_3947 | Boyles law was discovered in the 1600s by an Irish chemist named Robert Boyle. According to Boyles law, if the temperature of a gas is held constant, increasing the volume of the gas decreases its pressure. Why is this the case? As the volume of a gas increases, its particles have more room to spread out. This means that there are fewer particles bumping into any given area. This decreases the pressure of the gas. The graph in Figure 4.12 shows this relationship between volume and pressure. Because pressure and volume change in opposite directions, their relationship is called an inverse relationship. You can see an animation of the relationship at this URL: A scuba diver, like the one in Figure 4.13, releases air bubbles when he breathes under water. As he gets closer to the surface of the water, the air bubbles get bigger. Boyles law explains why. The pressure of the water decreases as the diver gets closer to the surface. Because the bubbles are under less pressure, they increase in volume even though the amount of gas in the bubbles remains the same. | text | null |
L_0770 | behavior of gases | T_3947 | Boyles law was discovered in the 1600s by an Irish chemist named Robert Boyle. According to Boyles law, if the temperature of a gas is held constant, increasing the volume of the gas decreases its pressure. Why is this the case? As the volume of a gas increases, its particles have more room to spread out. This means that there are fewer particles bumping into any given area. This decreases the pressure of the gas. The graph in Figure 4.12 shows this relationship between volume and pressure. Because pressure and volume change in opposite directions, their relationship is called an inverse relationship. You can see an animation of the relationship at this URL: A scuba diver, like the one in Figure 4.13, releases air bubbles when he breathes under water. As he gets closer to the surface of the water, the air bubbles get bigger. Boyles law explains why. The pressure of the water decreases as the diver gets closer to the surface. Because the bubbles are under less pressure, they increase in volume even though the amount of gas in the bubbles remains the same. | text | null |
L_0770 | behavior of gases | T_3948 | Charless law was discovered in the 1700s by a French physicist named Jacques Charles. According to Charless law, if the pressure of a gas is held constant, increasing the temperature of the gas increases its volume. What happens when a gas is heated? Its particles gain energy. With more energy, the particles have a greater speed. Therefore, they can move more and spread out farther. The volume of the gas increases as it expands and takes up more space. The graph in Figure 4.14 shows this relationship between the temperature and volume of a gas. You can see an animation of the relationship at this URL: . Roger had a latex balloon full of air inside his air-conditioned house. When he took the balloon outside in the hot sun, it got bigger and bigger until it popped. Charless law explains why. As the gas in the balloon warmed in the sun, its volume increased. It stretched and expanded the latex of the balloon until the balloon burst. | text | null |
L_0770 | behavior of gases | T_3949 | Amontons law was discovered in the late 1600s by a French physicist named Guillaume Amonton. According to Amontons law, if the volume of a gas is held constant, increasing the temperature of the gas increases its pressure. Why is this the case? A heated gas has more energy. Its particles move more and have more collisions, so the pressure of the gas increases. The graph in Figure 4.15 shows this relationship. A woman checked the air pressure in her tires before driving her car on a cold day (see Figure 4.16). The tire pressure gauge registered 29 pounds of pressure per square inch. After driving the car several miles on the highway, the woman stopped and checked the tire pressure again. This time the gauge registered 32 pounds per square inch. Amontons law explains what happened. As the tires rolled over the road, they got warmer. The air inside the tires also warmed. As it did, its pressure increased. | text | null |
L_0770 | behavior of gases | T_3949 | Amontons law was discovered in the late 1600s by a French physicist named Guillaume Amonton. According to Amontons law, if the volume of a gas is held constant, increasing the temperature of the gas increases its pressure. Why is this the case? A heated gas has more energy. Its particles move more and have more collisions, so the pressure of the gas increases. The graph in Figure 4.15 shows this relationship. A woman checked the air pressure in her tires before driving her car on a cold day (see Figure 4.16). The tire pressure gauge registered 29 pounds of pressure per square inch. After driving the car several miles on the highway, the woman stopped and checked the tire pressure again. This time the gauge registered 32 pounds per square inch. Amontons law explains what happened. As the tires rolled over the road, they got warmer. The air inside the tires also warmed. As it did, its pressure increased. | text | null |
L_0795 | air pressure and altitude | T_4113 | Because gas particles in the airlike particles of all fluidsare constantly moving and bumping into things, they exert pressure. The pressure exerted by the air in the atmosphere is greater close to Earths surface and decreases as you go higher above the surface. You can see this in the Figure 1.1. Q: Denver, Colorado, is called the mile-high city because it is located 1 mile (1.6 km) above sea level. What is the average atmospheric pressure that high above sea level? A: From the Figure 1.1, the average atmospheric pressure 1.6 km above sea level is about 85 kPa. | text | null |
L_0795 | air pressure and altitude | T_4114 | There are two reasons why air pressure decreases as altitude increases: density and depth of the atmosphere. Most gas molecules in the atmosphere are pulled close to Earths surface by gravity, so gas particles are denser near the surface. With more gas particles in a given volume, there are more collisions of particles and therefore greater pressure. The depth (distance from top to bottom) of the atmosphere is greatest at sea level and decreases at higher altitudes. With greater depth of the atmosphere, more air is pressing down from above. Therefore, air pressure is greatest at sea level and falls with increasing altitude. On top of Mount Everest, which is the tallest mountain on Earth, air pressure is only about one-third of the pressure at sea level. | text | null |
L_0795 | air pressure and altitude | T_4115 | The pressure of air in the atmosphere allows us to do many things, from sipping through a straw to simply breathing. You can see in the Figures 1.2 and 1.3 how we use air pressure in both of these ways. When you first suck on a straw, you remove air from the straw, so the air pressure in the straw is lower that the air pressure on the surface of the drink. A fluid always flows from an area of higher pressure to an area of lower pressure, so the drink moves up the straw and into your mouth. | text | null |
L_0795 | air pressure and altitude | T_4115 | The pressure of air in the atmosphere allows us to do many things, from sipping through a straw to simply breathing. You can see in the Figures 1.2 and 1.3 how we use air pressure in both of these ways. When you first suck on a straw, you remove air from the straw, so the air pressure in the straw is lower that the air pressure on the surface of the drink. A fluid always flows from an area of higher pressure to an area of lower pressure, so the drink moves up the straw and into your mouth. | text | null |
L_0799 | amontonss law | T_4125 | There was no additional air in the tire the second time Lawrence checked the air pressure, but something did change between the two measurements. The tires had rolled over 10 miles of road on the trip to school. Any time one surface moves over another, it causes friction. Friction is a force that opposes the motion of two surfaces that are touching, and friction between two surfaces always generates heat. Quickly rub your hands together and youll feel the heat generated by the friction between them. As the tires moved over the road, friction between the tires and road generated heat. In short, the tires got warmer and so did the air inside them. | text | null |
L_0799 | amontonss law | T_4126 | The space inside a car tire is more-or-less fixed, so it has a constant volume. What happens when the volume of air is constant and its temperature increases? Lawrence found out the answer to that question when he measured the air pressure in his tire. Increasing the temperature of a gas such as air, while holding its volume constant, increases the pressure of the gas. This relationship between temperature and pressure of a gas is called Amontons law. It was first proposed by a French scientist named Guillaume Amontons in the late 1600s. Amontons gas law is just one of three commonly known gas laws. The other two are Boyles law and Charles law. Q: How does Amontons gas law explain the difference in air pressure in Lawrences tire? A: The tireand the air inside itgot warmer because of friction with the road. The volume of air inside the tire was more-or-less constant, so the pressure of the air increased when it got warmer. | text | null |
L_0799 | amontonss law | T_4127 | Why does the pressure of a gas increase as it gets warmer? Particles of a gas are constantly moving and bumping into things. The force of the collisions is measured by pressure. Pressure is the amount of force exerted on a given area, such as pounds of force per square inch. When gas particles heat up and gain energy, they move faster. This causes more collisions and greater pressure. Therefore, heating particles of gas in a closed space causes the pressure of the gas to increase. | text | null |
L_0807 | bernoullis law | T_4156 | Bernoullis law states that the pressure of a moving fluid such as air is less when the fluid is moving faster. Pressure is the amount of force applied per given area. The law is named for Daniel Bernoulli, a Swiss mathematician who discovered it during the 1700s. Bernoulli used mathematics to arrive at his law. | text | null |
L_0807 | bernoullis law | T_4157 | Did you ever wonder how the wings of airplanes or birds allow them to fly? Bernoullis law provides the answer. Look at the wings of the plane and hawk in the Figure 1.1. The shape of the wings causes air to flow more slowly below them than above them. This causes air pressure to be greater below the wings than above them. The difference in air pressure lifts the plane or bird above the ground. Q: How does a spoiler on a racecar use Bernoullis law? A: A spoiler on a racecar is like an upside-down wing. Its shape causes air to flow more slowlyand air pressure to be greaterabove the spoiler than below it. As a result, air pressure pushes the car downward, helping it to stay on the track. | text | null |
L_0814 | boyles law | T_4178 | What does popping bubble wrap have to do with science? Actually, it demonstrates an important scientific law, called Boyles law. Like other laws in science, this law describes what always happens under certain conditions. Boyles law is one of three well-known gas laws, which state the relationships among temperature, volume, and pressure of gases. (The other two gas laws are Charles law and Amontons law.) According to Boyles law, if the temperature of a gas is held constant, then decreasing the volume of the gas increases its pressureand vice versa. Thats what happens when you squeeze the bubbles of bubble wrap. You decrease the bubbles volume, so the air pressure inside the bubbles increases until they pop. | text | null |
L_0814 | boyles law | T_4179 | Boyles law is named for Robert Boyle, the English scientist who discovered this relationship between gas volume and pressure. Boyle based the law on his own controlled experiments. He published his results, along with detailed descriptions of his procedures and observations, in the 1660s. These steps were unheard of in his day. Mainly because of his careful research and the details he provided about it, Boyle has been called the father of modern chemistry. | text | null |
L_0814 | boyles law | T_4180 | Imagine a container of gas molecules like the one in the Figure 1.1. The container in the sketch has a lid that can be pushed down to shrink the volume of the gas inside. Notice what happens as the lid is lowered. The gas molecules crowd closer together because there is less space for them to occupy and they have nowhere else to go. Gas molecules have a lot of energy. They are always moving and bouncing off each other and anything else in their path. When gas molecules bump into things, it creates pressure. Pressure is greater when gas molecules occupy a smaller space, because the greater crowding results in more collisions. In other words, decreasing the volume of a gas increases its pressure. | text | null |
L_0814 | boyles law | T_4181 | As the volume of gas in the container pictured in the Figure 1.1 gets smaller, the pressure of the gas molecules becomes greater. When two variables change in opposite directions like this, the variables have an inverse, or upside-down, relationship. Q: How could you show an inverse relationship with a graph? Sketch a graph to show what the relationship between gas volume and pressure might look like. Let the x-axis represent volume (V) and the y-axis represent pressure (P). A: Did you sketch a graph like the one in the Figure 1.2? Lets see why this graph is correct. Find the point on the line where volume is smallest. Thats were pressure is highest. Then find the point where volume is largest. Thats where pressure is lowest. Whenever you see a graph with this shape, it usually represents variables that have an inverse relationship, like gas volume and pressure. | text | null |
L_0826 | charless law | T_4217 | The popularity of hot air balloons got scientists thinking about gases and what happens to them when they heat up. In the early 1800s, two French scientistsJacques Charles and Joseph Gay-Lussacdecided to investigate how changes in the temperature of a gas affect the amount of space it takes up, or its volume. They heated air and measured how its volume changed. The two scientists already knew that the pressure of a gas affects it volume. This had been demonstrated back in the 1660s by the English scientist Robert Boyle. So Charles and Gay-Lussac controlled the effects of pressure by keeping it constant in their experiments. Based on the results of the research, Charles developed a scientific law about gases. It is one of three well-known gas laws, the others being Boyles law and Amontons law. According to Charless law, when the pressure of a gas is held constant, increasing its temperature increases its volume. The opposite is also true: decreasing the temperature of a gas decreases it volume. | text | null |
L_0839 | communication in science | T_4256 | The last step of most scientific investigations is reporting the results. When scientists communicate their findings, they add to the body of scientific knowledge, and thats how science advances. Science generally builds on previous knowledge, sometimes advancing in giant steps but more often in baby steps. The brick building analogy in the Figure 1.1 may help you better understand why communication is important in science. When scientists communicate about their research, they may also get useful feedback from other scientists. For example, comments from other scientists might help them improve their research design or interpret their findings in a different way. Other scientists can also repeat the research to see if they get the same results. Q: Why might it be important for other scientists to repeat an investigation? A: If an investigation is repeated and different results are obtained, then it throws doubt on the original research. On the other hand, if the same results are obtained, scientists can place more confidence in them. | text | null |
L_0839 | communication in science | T_4257 | The posters shown in the opening image are just one of several ways that scientists may communicate about their research. Some of the most common ways scientists communicate are listed below. You can think of scientific knowledge as a brick building, and the work of a single sci- entist as an individual brick. Considered by itself, the work of a single scientist may not seem that important, yet it may be an important piece of the overall structure. But unless a scientist communicates re- search results, that single brick may never be added to the building. Scientists may present papers about their research at scientific conferences. This is a good way to quickly reach an audience of other scientists who are most interested in the research topic. Scientists may publish articles about their research in peer-reviewed science journals. Peer review means that the work is analyzed by peers, in other words, by other scientists. The articles are published only if the other scientists are convinced that the research is accurate and honest. Scientists may testify about their research before congress if their findings relate to matters of public policy, such as environmental pollution. Scientists may communicate about their research to the general public. For example, they might create a Web site about their research, blog about it, or write articles for newspapers or magazines. Q: Why might it be important for scientists to communicate about their research to the general public? Give an example. A: Communicating to the general public might be important if the research is directly related to peoples lives. For example, assume that a scientist has investigated how driving habits are related to car crashes. She might write a newspaper article to share the research results with the public so they can adopt driving habits that reduce the risk of crashes. | text | null |
L_0895 | ethics in science | T_4429 | Ethics refers to deciding whats right and whats wrong. Making ethical decisions involves weighing right and wrong in order to make the best choice. The ethical problem of the Pacific yew has both right and wrong aspects. Its right to save lives with the cancer drug that comes from the tree bark, but its wrong to endanger the tree and risk its extinction. Q: What do you think is the most ethical decision about the Pacific yew? Should the bark be used to make the drug and possibly save human lives? Or should this be prohibited in order to protect the tree from possible extinction? A: This is tough ethical dilemma, and there is no right or wrong answer. Ethical dilemmas such as this often spur scientists to come up with new solutions to problems. Thats what happened in the case of the Pacific yew. Scientists tackled and solved the problem of determining the chemical structure of the anti-cancer drug so it could be synthesized in labs. This is a win-win solution to the problem. The synthetic drug is now available to save lives, and the trees are no longer endangered by being stripped of their bark. | text | null |
L_0895 | ethics in science | T_4430 | Ethics is an important consideration in science. Scientific investigations must be guided by what is right and what is wrong. Thats where ethical rules come in. They help ensure that science is done safely and that scientific knowledge is reliable. Here are some of the ethical rules that scientists must follow: Scientific research must be reported honestly. It is wrong and misleading to make up or change research results. Scientific researchers must try to see things as they really are. They should avoid being biased by the results they expect or hope to get. Researchers must be careful. They should do whatever they can to avoid errors in their data. Researchers must inform coworkers and members of the community about any risks of their research. They should do the research only if they have the consent of these groups. Researchers studying living animals must treat them humanely. They should provide for their needs and take pains to avoid harming them. Researchers studying human subjects must tell their subjects that they have the right to refuse to participate in the research. Human subjects also must be fully informed about their role in the research, including any potential risks. You can read about a terrible violation of this ethical rule in the Figure 1.1. | text | null |
L_0895 | ethics in science | T_4431 | Sometimes, science can help people make ethical decisions in their own lives. For example, scientific evidence shows that certain human actionssuch as driving cars that burn gasolineare contributing to changes in Earths climate. This, in turn, is causing more severe weather and the extinction of many species. A number of ethical decisions might be influenced by this scientific knowledge. Q: For example, should people avoid driving cars to work or school because it contributes to climate change and the serious problems associated with it? What if driving is the only way to get there? Can you think of an ethical solution? A: This example shows that ethical decisions may not be all or nothing. For example, rather than driving alone, people might carpool with others. This would reduce their impact on climate change. They could also try to reduce their impact in other ways. For example, they might turn down their thermostat in cold weather so their furnace burns less fuel. | text | null |
L_0900 | field study | T_4443 | Although experiments are the gold standard for scientific investigations, sometimes its not possible or desirable to do experiments. Often its important to investigate a problem in the real world instead of in a lab. An investigation that gathers evidence in the real worldas the environmental chemist above is doingis called a field study. Q: Why are field studies important for environmental scientists? A: To learn about the environment, scientists need to take measurements and make observations in the real world. This means gathering evidence in field studies; collecting samples of water from a river is one example of this method. | text | null |
L_0900 | field study | T_4444 | The environmental scientist above will gather samples of river water in several different locations. Then he will take the samples back to a lab to analyze them. He will do tests to identify any pollutants in the samples. Taking samples from different locations may help him identify the source of any pollution he finds. Pollution can enter a river from a single source, such as a waste water pipe from a factory. This is called point-source pollution. Or pollution can enter a river in runoff rainwater that picks up pollutants as it runs over the ground. This type of pollution enters the river everywhere. This is called nonpoint-source pollution. Q: Assume that the river is polluted only by nonpoint-source pollution. Describe how the samples of river water would compare in terms of the pollutants they contain. A: All of the samples would contain about the same amount and types of pollutants. Q: How might point-source pollution be identified? A: Just one sample might be polluted. This would be the sample taken at, or just downstream from, the single source of pollution. | text | null |
L_0909 | gases | T_4469 | A gas is one of four well-known states of matter. (The other three are solid, liquid, and plasma). The particles of a gas can pull apart from each other and spread out. As a result, a gas does not have a fixed shape or a fixed volume. In fact, a gas always spreads out to take up whatever space is available to it. If a gas is enclosed in a container, it spreads out until it has the same volume as the container. Q: The sketches in the Figure 1.1 represent two identical sealed boxes that contain only air particles (represented by dots). There are more air particles in box B than box A. Which box contains a greater volume of air? A: This is a trick question! The air inside each box expands to fill the available space, which is identical for both boxes. There are more air particles in box B, but the volume of air is exactly the same in both boxes. | text | null |
L_0909 | gases | T_4470 | Particles of gas are constantly moving in all directions at random. As a result, they are always bumping into each other and other things. This is modeled in the Figure 1.2. The force of the particles against things they bump into creates pressure. Pressure is defined in physics as the amount of force pushing against a given area. How much pressure a gas exerts depends on the number of gas particles in a given space and how fast they are moving. The more gas particles there are and the faster they are moving, the greater the pressure they create. The arrows show that particles of a gas move randomly in all directions. Q: Look at box A and box B in the previous question. Is air pressure the same in both boxes? Why or why not? A: Air pressure is greater in box B. Thats because there are more air particles in box B to bump into each other and into the sides of the container. Therefore, the particles in box B exert more force on a given area. | text | null |
L_0909 | gases | T_4470 | Particles of gas are constantly moving in all directions at random. As a result, they are always bumping into each other and other things. This is modeled in the Figure 1.2. The force of the particles against things they bump into creates pressure. Pressure is defined in physics as the amount of force pushing against a given area. How much pressure a gas exerts depends on the number of gas particles in a given space and how fast they are moving. The more gas particles there are and the faster they are moving, the greater the pressure they create. The arrows show that particles of a gas move randomly in all directions. Q: Look at box A and box B in the previous question. Is air pressure the same in both boxes? Why or why not? A: Air pressure is greater in box B. Thats because there are more air particles in box B to bump into each other and into the sides of the container. Therefore, the particles in box B exert more force on a given area. | text | null |
L_0909 | gases | T_4471 | We live in a sea of air called the atmosphere. Can you feel the air in the atmosphere pressing against you? Not usually, but air actually exerts a lot of pressure because theres so much of it. The atmosphere rises high above Earths surface, so it contains a huge number of gas particles. Most of them are concentrated close to Earths surface because of gravity and the weight of all the air in the atmosphere above them. As a result, air pressure is greatest at sea level and drops rapidly as you go higher in altitude. The Figure 1.3 shows how air pressure falls from sea level to the top of the atmosphere. In the graph, air pressure is measured in a unit called the millibar (mb). The SI unit of pressure is newton per square centimeter (N/cm2 ). Q: The top of Mount Everest is almost 9 km above sea level. What is the pressure of the atmosphere at this altitude? A: Air pressure at the top of Mount Everest is about 260 mb. This is only about 25 percent of air pressure at sea level, which is 1013.2 mb. No wonder its hard for climbers to breathe when they get close to Mount Everests summit! | text | null |
L_0918 | history of science | T_4503 | People have probably wondered about the natural world for as long as there have been people. So its no surprise that science has roots that go back thousands of years. Some of the earliest contributions to science were made by Greek philosophers more than two thousand years ago. It wasnt until many centuries later, however, that the scientific method and experimentation were introduced. The dawn of modern science occurred even more recently. It is generally traced back to the scientific revolution, which took place in Europe starting in the 1500s. | text | null |
L_0918 | history of science | T_4504 | A Greek philosopher named Thales, who lived around 600 BCE, has been called the father of science for his ideas about the natural world. He proposed that natural events such as lightning and earthquakes have natural causes. Up until then, people understood such events to be the acts of gods or other supernatural forces. Q: Why was Thales idea about natural causes such an important contribution to science? A: Natural causes can be investigated and understood, whereas gods or other supernatural causes are above nature and not suitable for investigation. Just a few hundred years after Thales, the Greek philosopher Aristotle made a very important contribution to science. You can see what Aristotle looked like in the Figure 1.1. Prior to Aristotle, other philosophers believed that they could find the truth about the natural world by inward reflectionin other words, just by thinking about it. Aristotle, in contrast, thought that truth about the natural world could come only from observations of nature and inductive reasoning. He argued that knowledge of nature must be based on evidence and logic. This idea is called empiricism, and it is the basis of science today. Aristotle introduced the idea of empiricism around 350 BCE. It is a hallmark of modern science. | text | null |
L_0918 | history of science | T_4505 | In the first 1000 years CE, Europe went through a period called the Dark Ages. Science and learning in general were all but abandoned. However, in other parts of the world science flourished. During this period, some of the most important contributions to science were made by Persian scholars. For example, during the 700s CE, a Persian scientist named Geber introduced the scientific method and experimentation in chemistry. His ideas and methods were later adopted by European chemists. Today, Geber is known as the father of chemistry. | text | null |
L_0918 | history of science | T_4506 | Starting in the mid-1500s, a scientific revolution occurred in Europe. This was the beginning of modern Western science. Many scientific advances were made during a period of just a couple of hundred years. The revolution in science began when Copernicus made the first convincing arguments that the sunnot Earthis the center of what we now call the solar system. (You can see both models of the solar system in the Figure 1.2.) This was a drastic shift in thinking about Earths place in the cosmos. Around 1600, the Italian scientist Galileo greatly improved the telescope, which had just been invented, and made many important discoveries in the field of astronomy. Some of Galileos observations provided additional evidence for Copernicus sun-centered solar system. Q: Copernicus ideas about the solar system were so influential that the scientific revolution is sometimes called the Copernican revolution. Why do you think Copernicus ideas led to a revolution in science? A: Copernicus ideas about the solar system are considered to be the starting point of modern astronomy. They changed how all future scientists interpreted observations in astronomy. They also led to a flurry of new scientific investigation. Other contributions to science that occurred during the scientific revolution include: Keplers laws of planetary motion The model on the left shows what people believed about the solar system before Copernicus introduced the model on the right. Newtons law of universal gravitation Newtons three laws of motion | text | null |
L_0918 | history of science | T_4507 | Another major shift in science occurred with the work of Albert Einstein (the rock star scientist pictured in the opening image). In 1916, Einstein published his general theory of relativity. This theory relates matter and energy. It also explains gravity as a property of space and time (rather than a property of matter as Newton thought). Einsteins theory has been supported by all evidence and observations to date, whereas Newtons law of gravity does not apply to all cases. Einsteins theory is still the accepted explanation for gravity today. Q: How might Einsteins theory have influenced the course of science? A: Einsteins theory suggested new areas of investigation. Many predictions based on the theory were later found to be true. For example, black holes in the universe were predicted by Einsteins theory and later confirmed by scientific evidence. | text | null |
L_0922 | hypothesis | T_4520 | The word hypothesis can be defined as an "educated guess." For example, it might be an educated guess about why a natural event occurs. But not all hypotheseseven those about the natural worldare scientific hypotheses. What makes a statement a scientific hypothesis rather than just an educated guess? A scientific hypothesis must meet two criteria: A scientific hypothesis must be testable. A scientific hypothesis must be falsifiable. | text | null |
L_0922 | hypothesis | T_4521 | For a hypothesis to be testable means that it is possible to make observations that agree or disagree with it. If a hypothesis cannot be tested by making observations, it is not scientific. Consider this statement: "There are invisible creatures all around us that we can never observe in any way." This statement may or may not be true, but it is not a scientific hypothesis. Thats because it cant be tested. Given the nature of the hypothesis, there are no observations a scientist could make to test whether or not it is false. | text | null |
L_0922 | hypothesis | T_4522 | A hypothesis may be testable, but even that isnt enough for it to be a scientific hypothesis. In addition, it must be possible to show that the hypothesis is false if it really is false. Consider this statement: There are other planets in the universe where life exists. This statement is testable. If it is true, it is at least theoretically possible to find evidence showing that its true. For example, a spacecraft could be sent from Earth to explore the universe and report back if it discovers an inhabited planet. If such a planet were found, it would prove the statement is true. However, the statement isnt a scientific hypothesis. Why? If it is false, its not possible to show that its false. The spacecraft may never find an inhabited planet, but that doesnt necessarily mean there isnt one. Given the vastness of the universe, we would never be able to check every planet for life! | text | null |
L_0922 | hypothesis | T_4523 | Lets consider one last example, which is illustrated in the Figure 1.1: "Any two objects dropped at the same time from the same height will reach the ground at the same time (assuming the absence of air resistance)." Is this statement testable? Yes. You could drop two objects at the same time from the same height and observe when they reach the ground. Of course, you would have to drop the objects in the absence of air to prevent air resistance, but at least such a test is theoretically possible. Is the statement falsifiable if it really is false? Again, the answer is yes. You can easily test many combinations of two objects and if any two objects do not reach the ground at the same time, then the hypothesis is false. If a hypothesis really is false, it should be relatively easy to disprove it. | text | null |
L_0922 | hypothesis | T_4524 | If the hypothesis above about falling objects really were false, it is likely that this would be discovered sooner or later after enough objects had been dropped. It takes just one exception to disprove a hypothesis. But what if the hypothesis really is true? Can this be demonstrated as well? No; it would require testing all possible combinations of objects to show that they always reach the ground at the same time. This is impossible. New objects are being made all the time that would have to be tested. Its always possible an exception would be found in the future to disprove the hypothesis. Although you cant prove conclusively that a hypothesis is true, the more evidence you gather in support of it, the more likely it is to be true. | text | null |
L_0961 | nature of science | T_4644 | Science is more about gaining knowledge than it is about simply having knowledge. Science is a way of learning about the natural world that is based on evidence and logic. In other words, science is a process, not just a body of facts. Through the process of science, our knowledge of the world advances. | text | null |
L_0961 | nature of science | T_4645 | Scientists may focus on very different aspects of the natural world. For example, some scientists focus on the world of tiny objects, such as atoms and molecules. Other scientists devote their attention to huge objects, such as the sun and other stars. But all scientists have at least one thing in common. They want to understand how and why things happen. Achieving this understanding is the goal of science. Have you ever experienced the thrill of an exciting fireworks show like the one pictured in the Figure 1.1? Fireworks show how the goal of science leads to discovery. Fireworks were invented at least 2000 years ago in China, but explaining how and why they work didnt happen until much later. It wasnt until scientists had learned about elements and chemical reactions that they could explain what caused fireworks to create brilliant bursts of light and deep rumbling booms. Fireworks were invented long before sci- entists could actually explain how and why they explode. | text | null |
L_0961 | nature of science | T_4646 | Sometimes learning about science is frustrating because scientific knowledge is always changing. But thats also what makes science exciting. Occasionally, science moves forward in giant steps. More commonly, however, science advances in baby steps. Giant steps in science may occur if a scientist introduces a major new idea. For example, in 1666, Isaac Newton introduced the idea that gravity is universal. People had long known that things fall to the ground because they are attracted by Earth. But Newton proposed that everything in the universe exerts a force of attraction on everything else. This idea is known as Newtons law of universal gravitation. Q: How do you think Newtons law of universal gravitation might have influenced the advancement of science? A: Newtons law allowed scientists to understand many different phenomena. It explains not only why things always fall down toward the ground or roll downhill. It also explains the motion of many other objects. For example, it explains why planets orbit the sun. The idea of universal gravity even helped scientists discover the planets Neptune and Pluto. The caption and diagram in the Figure 1.2 explain how. Baby steps in science occur as small bits of evidence gradually accumulate. The accumulating evidence lets scientists refine and expand on earlier ideas. For example, the scientific idea of the atom was introduced in the early 1800s. But scientists came to understand the structure of the atom only as evidence accumulated over the next two centuries. Their understanding of atomic structure continues to expand today. The advancement of science is sometimes a very bumpy road. New knowledge and ideas arent always accepted at first, and scientists may be mocked for their ideas. The idea that Earths continents drift on the planets surface is a good example. This idea was first proposed by a scientist named Alfred Wegener in the early 1900s. Wegener also proposed that all of the present continents had once formed one supercontinent, which he named Pangaea. You can see a sketch of Pangaea in Figure 1.3. Other scientists not only rejected Wegeners ideas, but ridiculed Wegener for even suggesting them. It wasnt until the 1950s that enough evidence had accumulated for scientists to realize that Wegener had been right. Unfortunately, Wegener did not live long enough to see his ideas accepted. A: Several types of evidence support Wegeners ideas. For example, similar fossils and rock formations have been found on continents that are now separated by oceans. It is also now known that Earths crust consists of rigid plates that slide over molten rock below them. This explains how continents can drift. Even the shapes of todays continents show how they once fit together, like pieces of a giant jigsaw puzzle. | text | null |
L_0961 | nature of science | T_4646 | Sometimes learning about science is frustrating because scientific knowledge is always changing. But thats also what makes science exciting. Occasionally, science moves forward in giant steps. More commonly, however, science advances in baby steps. Giant steps in science may occur if a scientist introduces a major new idea. For example, in 1666, Isaac Newton introduced the idea that gravity is universal. People had long known that things fall to the ground because they are attracted by Earth. But Newton proposed that everything in the universe exerts a force of attraction on everything else. This idea is known as Newtons law of universal gravitation. Q: How do you think Newtons law of universal gravitation might have influenced the advancement of science? A: Newtons law allowed scientists to understand many different phenomena. It explains not only why things always fall down toward the ground or roll downhill. It also explains the motion of many other objects. For example, it explains why planets orbit the sun. The idea of universal gravity even helped scientists discover the planets Neptune and Pluto. The caption and diagram in the Figure 1.2 explain how. Baby steps in science occur as small bits of evidence gradually accumulate. The accumulating evidence lets scientists refine and expand on earlier ideas. For example, the scientific idea of the atom was introduced in the early 1800s. But scientists came to understand the structure of the atom only as evidence accumulated over the next two centuries. Their understanding of atomic structure continues to expand today. The advancement of science is sometimes a very bumpy road. New knowledge and ideas arent always accepted at first, and scientists may be mocked for their ideas. The idea that Earths continents drift on the planets surface is a good example. This idea was first proposed by a scientist named Alfred Wegener in the early 1900s. Wegener also proposed that all of the present continents had once formed one supercontinent, which he named Pangaea. You can see a sketch of Pangaea in Figure 1.3. Other scientists not only rejected Wegeners ideas, but ridiculed Wegener for even suggesting them. It wasnt until the 1950s that enough evidence had accumulated for scientists to realize that Wegener had been right. Unfortunately, Wegener did not live long enough to see his ideas accepted. A: Several types of evidence support Wegeners ideas. For example, similar fossils and rock formations have been found on continents that are now separated by oceans. It is also now known that Earths crust consists of rigid plates that slide over molten rock below them. This explains how continents can drift. Even the shapes of todays continents show how they once fit together, like pieces of a giant jigsaw puzzle. | text | null |
L_0973 | observation | T_4684 | An observation is any information that is gathered with the senses. Our senses include vision, hearing, touch, smell, and taste. We see with our eyes, hear with our ears, touch with our hands, smell with our nose, and taste with our tongue. We can also extend our senses and our ability to make observations by using instruments such as microscopes, telescopes, and thermometers. Q: How do these instruments extend human senses and our ability to make observations? A: Microscopes and telescopes extend the sense of vision. They allow us to observe objects that are too small (microscopes) or too distant (telescopes) for the unaided eye to see. Thermometers extend the sense of touch. Using our sense of touch, we can only feel how warm or cold something is relative to our own temperature or the temperature of something else. Thermometers allow us to measure precisely how warm or cold something is. | text | null |
L_0973 | observation | T_4685 | Besides raising questions for investigation, observations play another role in scientific investigations. They help scientists gather evidence. For example, to investigate whether a chemical change has occurred, a scientist might observe whether certain telltale signs are present. In some chemical changes, for example, a substance turns from one color to another. You can see an example of this in the Figure 1.1. In other chemical changes, an odor is produced or gas bubbles are released. All of these changes can be observed with the senses. Some of these pennies are shiny and copper colored. Thats how pennies look when they are new. The older pennies are dull and brown. Copper at the surface of these pennies has combined with air to become a different substance with different properties. The change in color shows that a chemical change has occurred. Q: Some chemical changes release heat. How could this change be observed? A: The sense of touchor a thermometercould be used to observe an increase in temperature. | text | null |
L_0974 | oceanic pressure | T_4686 | Pressure is the amount of force acting on a given area. As you go deeper in the ocean, the pressure exerted by the water increases steadily. Thats because there is more and more water pressing down on you from above. The Figure 1.1 shows how pressure changes with depth. For each additional meter below the surface, pressure increases by 10 kPa. At 30 meters below the surface, the pressure is double the pressure at the surface. At a depth greater than 500 meters, the pressure is too great for humans to withstand without special equipment to protect them. At nearly 11,000 meters below the surface, the pressure is tremendous. | text | null |
L_0974 | oceanic pressure | T_4687 | Scuba divers can dive without special vehicles because they dont go very deep below the surface of the water. Nonetheless, because of the pressure of the water, scuba divers who go deeper than about 40 meters must return to the surface slowly. They must stop for several minutes at one or more points in their ascent. Thats what the divers in the Figure 1.2 are doing. The stops are needed to let the pressure inside their body adjust to the decreasing pressure of the water as they swim closer to the surface. If they were to rise to the surface too quickly, the gases dissolved in their blood would form bubbles and cause serious health problems. Q: Why would dissolved gases form bubbles as pressure decreases? A: Less gas can dissolve in a fluid at lower pressure. Therefore, as pressure decreases, gases come out of solution and form bubbles. | text | null |
L_0978 | pascals law | T_4699 | Pressure is the amount of force acting on a given area. It is represented by the equation: Pressure = Force Area The pressure exerted by a fluid increases if more force is applied or if the same force is applied over a smaller area. The equation for pressure can be rewritten as: Force = Pressure Area This equation shows that the same pressure applied to a greater area increases the force. | text | null |
L_0978 | pascals law | T_4700 | Some of the earliest scientific research on pressure in fluids was conducted by a French mathematician and physicist named Blaise Pascal (1623-1662). The SI unit of pressure, the Pascal (Pa), is named for him because of his important research. One of Pascals major contributions is known as Pascals law. This law states that a change in pressure at any point in an enclosed fluid is transmitted equally throughout the fluid. | text | null |
L_0978 | pascals law | T_4701 | A simple example may help you understand Pascals law. Toothpaste is a fluid that is enclosed in a tube with a small opening at one end. Look at the toothpaste tube in the Figure 1.1. When any part of the tube is squeezed, toothpaste squirts out the open end. The pressure applied to the tube is transmitted equally throughout the toothpaste. When the pressure reaches the open end, it forces toothpaste out through the opening. | text | null |
L_0978 | pascals law | T_4702 | The ability of fluids to transmit pressure in this way can be very usefulbesides getting toothpaste out of a tube! For example, hydraulic brakes in a car use fluid to transmit pressure, and when they do, they also increase force. You can see how hydraulic brakes work in the Figure 1.2. A: The arrows representing the force applied by the break cylinder are larger than the arrow representing the force applied by the brake pedal mechanism. A larger arrow indicates greater force. Q: How do hydraulic brakes increase the force that is applied to the brake shoes? A: The pressure exerted by the fluid on the brake shoes is applied over a larger area. When pressure acts over a larger area, it increases the force (Force = Pressure Area). Hydraulic car lifts also use fluid to transmit pressure and increase force. The lifts are used to raise cars, which are very heavy, so mechanics can work on them from underneath. Controls in airplanes use fluids to transmit pressure and increase force so a flick of a switch can raise or lower heavy landing gear. | text | null |
L_0983 | physical science careers | T_4713 | Physical science is the study of matter and energy. It includes the sciences of chemistry and physics. Most careers in physical science require a 4-year college degree in one of these fields. Some careers require more advanced education as well. For example, an astronaut might have a masters degree or even a doctoral degree. Q: Besides becoming an astronaut, a degree in physical science can prepare you for many other careers. What careers do you think might be available to people with degrees in physical science? A: People with degrees in physical science might become pharmacists, forensic technicians, or research scientists, to name just three possible careers. Four additional careers in physical science are described below. | text | null |
L_0983 | physical science careers | T_4714 | Training in the physical science field of chemistry or physics is needed for the careers described in the Figure 1.1. Do any of these careers interest you? | text | null |
L_0988 | pressure in fluids | T_4736 | All fluids exert pressure like the air inside a tire. The particles of fluids are constantly moving in all directions at random. As the particles move, they keep bumping into each other and into anything else in their path. These collisions cause pressure, and the pressure is exerted equally in all directions. When particles are crowded together in one part of an enclosed space, such as the air particles first entering a tire, they quickly spread out to fill all the available space. Thats because particles of fluids always move from an area of higher pressure to an area of lower pressure. This explains why air entering a tire through a tiny opening quickly fills the entire tire. | text | null |
L_0988 | pressure in fluids | T_4737 | Pressure is defined as the amount of force acting on a given area. Therefore, pressure can be represented by this equation: Pressure = Force Area Pressure shows how concentrated the force is on a given area. The smaller the area to which force is applied, the greater the pressure is. Think about pressing a pushpin, like the one in the Figure 1.1, into a bulletin board. You apply force with your thumb to the broad head of the pushpin. However, the force that the pushpin applies to the bulletin board acts only over the tiny point of the pin. This is a much smaller area, so the pressure the point applies to the bulletin board is much greater than the pressure you apply with your thumb. As a result, the pin penetrates the bulletin board with ease. | text | null |
L_0988 | pressure in fluids | T_4738 | In the above equation for pressure, force is expressed in Newtons (N) and area is expressed in square meters (m2 ). Therefore, pressure is expressed in N/m2 , which is the SI unit for pressure. This unit is also called the Pascal (Pa). It is named for the scientist Blaise Pascal whose discoveries about pressure in fluids led to a law of the same name. Pressure may also be expressed in the kilopascal (kPa), which equals 1000 Pascals. For example, the correct air pressure inside a mountain bike tire is usually about 200 kPa. | text | null |
L_0988 | pressure in fluids | T_4739 | When you know how much force is acting on a given area, you can calculate the pressure that is being applied to the area using the equation for pressure given above. For example, assume that a rock weighs 5000 N and is resting on the ground on an area of 0.5 m2 . The pressure exerted on the ground by the rock is: N = 10000 N/m2 = 10000 Pa, or 10 kPa Pressure = 5000 0.5 m2 Sometimes pressure but not force is known. To calculate force, the equation for pressure can be rewritten as: Force = Pressure Area For example, suppose another rock exerts 10 kPa of pressure over an area of 0.4 m2 . How much does the rock weigh? Change 10 kPa (10,000 Pa) to 10,000 N/m2 . Then substitute this value for pressure in the force equation as follows: Force (Weight) = 10,000 N/m2 0.4 m2 = 4,000 N Q: The break-dancer in the Figure 1.2 has a weight of 800 N. He is balancing on the palm of one hand. If the palm of his hand has an area of 0.02 m2 , how much pressure is he exerting on the ground? A: Use the equation for pressure: 800 N Pressure = 0.02 m2 = 40000 Pa, or 40 kPa Q: If the break-dancer lies down on the ground on his back, his weight is spread over an area of 0.75 m2 . How much pressure does he exert on the ground in this position? A: On his back, the pressure he exerts is: Pressure = 800 N 0.75 m2 = 1100 Pa, or 1.1 kPa | text | null |
L_0988 | pressure in fluids | T_4740 | Two factors influence the pressure of fluids. They are the depth of the fluid and its density. A fluid exerts more pressure at greater depths. Deeper in a fluid, all of the fluid above it results in more weight pressing down. This causes greater pressure the deeper you go. Denser fluids such as water exert more pressure than less dense fluids such as air. The particles of denser fluids are closer together, so there are more collisions of particles in a given area. The difference in density of water and air is illustrated in the Figure 1.3. | text | null |
L_1006 | replication in science | T_4797 | Scientists also have to check their work. The results of an investigation are not likely to be well accepted unless the investigation is repeatedusually many timesand the same result is always obtained. Getting the same result when an experiment is repeated is called replication. If research results can be replicated, it means they are more likely to be correct. Repeated replication of investigations may turn a hypothesis into a theory. On the other hand, if results cannot be replicated they are likely to be incorrect. | text | null |
L_1006 | replication in science | T_4798 | The following example shows why replication is important in science. In 1998, a British researcher published an article in a medical journal reporting that he had found a link between a common childhood vaccine and autism (see Figure 1.1). According to the article, children in his study developed autism soon after receiving the vaccine. Following publication of the article, many parents refused to have their children vaccinated. Several epidemics occurred as a result, and some children died of the diseases. Soon after the original study was published, other researchers tried to replicate the research. However, it could not be replicated. No other studies could find a link between the vaccine and autism. As a result, scientists became convinced that the original results were incorrect. Eventually, investigators determined that the original study was a fraud. They learned that its author had received a large amount of money to find evidence that the vaccine causes autism, so he faked his research results. If other scientists had not tried to replicate the research, the truth might never have come out. | text | null |
L_1008 | safety in science | T_4803 | Lab procedures and equipment may be labeled with safety symbols. These symbols warn of specific hazards, such as flames or broken glass. Learn the symbols so you will recognize the dangers. Then learn how to avoid them. Many common safety symbols are shown below. Q: Do you know how you can avoid these hazards? A: Wearing protective gear is one way to avoid many hazards in science. For example, to avoid being burned by hot objects, use hot mitts to protect your hands. To avoid eye hazards, such as harsh liquids splashed into the eyes, wear safety goggles. | text | null |
L_1008 | safety in science | T_4804 | Following basic safety rules is another important way to stay safe in science. Safe practices help prevent accidents. Several lab safety rules are listed below. Different rules may apply when you work in the field. But in all cases, you should always follow your teachers instructions. Lab Safety Rules Wear long sleeves and shoes that completely cover your feet. If your hair is long, tie it back or cover it with a hair net. Protect your eyes, skin, and clothing by wearing safety goggles, an apron, and gloves. Use hot mitts to handle hot objects. Never work in the lab alone. Never engage in horseplay in the lab. Never eat or drink in the lab. Never do experiments without your teachers approval. Always add acid to water, never the other way around, and add the acid slowly to avoid splashing. Take care to avoid knocking over Bunsen burners, and keep them away from flammable materials such as paper. Use your hand to fan vapors toward your nose rather than smelling substances directly. Never point the open end of a test tube toward anyoneincluding yourself! Clean up any spills immediately. Dispose of lab wastes according to your teachers instructions. Wash glassware and counters when you finish your work. Wash your hands with soap and water before leaving the lab. | text | null |
L_1008 | safety in science | T_4805 | Even when you follow the rules, accidents can happen. Immediately alert your teacher if an accident occurs. Report all accidents, whether or not you think they are serious. | text | null |
L_1011 | scientific experiments | T_4811 | An experiment is a controlled scientific study of specific variables. A variable is a factor that can take on different values. For example, the speed of an object down a ramp might be one variable, and the steepness of the ramp might be another. | text | null |
L_1011 | scientific experiments | T_4812 | There must be at least two variables in any experiment: a manipulated variable and a responding variable. A manipulated variable is a variable that is changed by the researcher. A manipulated variable is also called an independent variable. A responding variable is a variable that the researcher predicts will change if the manipulated variable changes. A responding variable is also called a dependent variable. You can learn how to identify manipulated and responding variables in an experiment by watching this video about bouncing balls: Click image to the left or use the URL below. URL: Q: If you were to do an experiment to find out what influences the speed of an object down a ramp, what would be the responding variable? How could you measure it? A: The responding variable would be the speed of the object. You could measure it indirectly with a stopwatch. You could clock the time it takes the object to travel from the top to the bottom of the ramp. The less time it takes, the faster the average speed down the ramp. Q: What variables might affect the speed of an object down a ramp? A: Variables might include factors relating to the ramp or to the object. An example of a variable relating to the ramp is its steepness. An example of a variable relating to the object is the way it movesit might roll or slide down the ramp. Either of these variables could be manipulated by the researcher, so you could choose one of them for your manipulated variable. | text | null |
L_1011 | scientific experiments | T_4813 | Assume you are sliding wooden blocks down a ramp in your experiment. You choose steepness of the ramp for your manipulated variable. You want to measure how changes in steepness affect the time it takes a block to reach the bottom of the ramp. You decide to test two blocks on two ramps, one steeper than the other, and see which block reaches the bottom first. You use a shiny piece of varnished wood for one ramp and a rough board for the other ramp. You raise the rough board higher so it has a steeper slope (see sketch below). You let go of both blocks at the same time and observe that the block on the ramp with the gentler slope reaches the bottom sooner. Youre surprised, because you expected the block on the steeper ramp to go faster and get to the bottom first. Q: What explains your result? A: The block on the steeper ramp would have reached the bottom sooner if all else was equal. The problem is that all else was not equal. The ramps varied not only in steepness but also in smoothness. The block on the smoother ramp went faster than the block on the rougher ramp, even though the rougher ramp was steeper. This example illustrates another important aspect of experiments: experimental controls. A control is a variable that must be held constant so it wont influence the outcome of an experiment. The control can be used as a standard for comparison between experiments. In the case of your ramp experiment, smoothness of the ramps should have been controlled by making each ramp out of the same material. For other examples of controls in an experiment, watch the video below. It is Part II of the above video on bouncing balls. Click image to the left or use the URL below. URL: Q: What other variables do you think might influence the outcome of your ramp experiment? How could these other variables be controlled? A: Other variables might include variables relating to the block. For example, a smoother block would be expected to go down a ramp faster than a rougher block. You could control variables relating to the block by using two identical blocks. | text | null |
L_1013 | scientific induction | T_4819 | Inductive reasoning is the process of drawing general conclusions based on many clues, or pieces of evidence. Many crimes are solved using inductive reasoning. It is also the hallmark of science and the basis of the scientific method. Q: How might the police detective pictured above use inductive reasoning to solve the crime? A: The detective might gather clues that provide evidence about the identity of the person who committed the crime. For example, he might find fingerprints or other evidence left behind by the perpetrator. The detective might eventually find enough clues to be able to conclude the identity of the most likely suspect. | text | null |
L_1013 | scientific induction | T_4820 | A simple example will help you understand how inductive reasoning works in science. Suppose you grew up on a planet named Quim, where there is no gravity. In fact, assume youve never even heard of gravity. You travel to Earth (on a student exchange program) and immediately notice things are very different here than on your home planet. For one thing, when you step out of your spacecraft, you fall directly to the ground. Then, when you let go of your communications device, it falls to the ground as well. On Quim, nothing ever falls to the ground. For example, if you had let go of your communications device back home, it would have just stayed in place by your upper appendage. You notice that everything you let go of falls to the ground. Using inductive reasoning, you conclude that all objects fall to the ground on Earth. Then, you make the observation pictured (Figure 1.2). You see round objects rising up into the sky, rather than falling toward the ground as you expect. Clearly, your first conclusionalthough based on many pieces of evidenceis incorrect. You need to gather more evidence to come to a conclusion that explains all of your observations. Evidence that not everything falls to the ground on Earth. Q: What conclusion might you draw based on the additional evidence of the balloons rising instead of falling? A: With this and other evidence, you might conclude that objects heavier than air fall to the ground but objects lighter than air do not. | text | null |
L_1013 | scientific induction | T_4820 | A simple example will help you understand how inductive reasoning works in science. Suppose you grew up on a planet named Quim, where there is no gravity. In fact, assume youve never even heard of gravity. You travel to Earth (on a student exchange program) and immediately notice things are very different here than on your home planet. For one thing, when you step out of your spacecraft, you fall directly to the ground. Then, when you let go of your communications device, it falls to the ground as well. On Quim, nothing ever falls to the ground. For example, if you had let go of your communications device back home, it would have just stayed in place by your upper appendage. You notice that everything you let go of falls to the ground. Using inductive reasoning, you conclude that all objects fall to the ground on Earth. Then, you make the observation pictured (Figure 1.2). You see round objects rising up into the sky, rather than falling toward the ground as you expect. Clearly, your first conclusionalthough based on many pieces of evidenceis incorrect. You need to gather more evidence to come to a conclusion that explains all of your observations. Evidence that not everything falls to the ground on Earth. Q: What conclusion might you draw based on the additional evidence of the balloons rising instead of falling? A: With this and other evidence, you might conclude that objects heavier than air fall to the ground but objects lighter than air do not. | text | null |
L_1013 | scientific induction | T_4821 | Inductive reasoning cant solve a crime or arrive at the correct scientific conclusion with 100 percent certainty. Its always possible that some piece of evidence remains to be found that would disprove the conclusion. Thats why jurors in a trial are told to decide whether the defendant is guilty without a reasonable doubtnot without a shred of doubt. Similarly, a scientific theory is never really proven conclusively to be true. However, it can be supported by so much evidence that it is accepted without a reasonable doubt. Click image to the left or use the URL below. URL: | text | null |
L_1014 | scientific law | T_4822 | It may seem like common sense that bumper cars change their motion when they collide. Thats because all objects behave this way - its the law! A scientific law, called Newtons third law of motion, states that for every action there is an equal and opposite reaction. Thus, when one bumper car acts by ramming another, one or both cars react by pushing apart. Q: What are some other examples of Newtons third law of motion? What actions are always followed by reactions? A: Other examples of actions and reactions include hitting a ball with a bat and the ball bouncing back; and pushing a swing and the swing moving away. | text | null |
L_1014 | scientific law | T_4823 | Newtons third law of motion is just one of many scientific laws. A scientific law is a statement describing what always happens under certain conditions. Other examples of laws in physical science include: Newtons first law of motion Newtons second law of motion Newtons law of universal gravitation Law of conservation of mass Law of conservation of energy Law of conservation of momentum | text | null |
L_1014 | scientific law | T_4824 | Scientific laws state what always happen. This can be very useful. It can let you let you predict what will happen under certain circumstances. For example, Newtons third law tells you that the harder you hit a softball with a bat, the faster and farther the ball will travel away from the bat. However, scientific laws have a basic limitation. They dont explain why things happen. Why questions are answered by scientific theories, not scientific laws. Q: You know that the sun always sets in the west. This could be expressed as a scientific law. Think of something else that always happens in nature. How could you express it as a scientific law? A: Something else that always happens in nature is water flowing downhill rather than uphill. This could be expressed as the law, When water flows over a hill, it always flows from a higher to a lower elevation. | text | null |
L_1017 | scientific process | T_4830 | Investigations are at the heart of science. They are how scientists add to scientific knowledge and gain a better understanding of the world. Scientific investigations produce evidence that helps answer questions. Even if the evidence cannot provide answers, it may still be useful. It may lead to new questions for investigation. As more knowledge is discovered, science advances. | text | null |
L_1017 | scientific process | T_4831 | Scientists investigate the world in many ways. In different fields of science, researchers may use different methods and be guided by different theories and questions. However, most scientists follow the general steps outlined in the Figure 1.1. This approach is sometimes called the scientific method. Keep in mind that the scientific method is a general approach and not a strict sequence of steps. For example, scientists may follow the steps in a different order. Or they may skip or repeat some of the steps. | text | null |
L_1017 | scientific process | T_4832 | A simple example will help you understand how the scientific method works. While Cody eats a bowl of cereal (Figure 1.2), he reads the ingredients list on the cereal box. He notices that the cereal contains iron. Cody is The general steps followed in the scientific method. studying magnets in school and knows that magnets attract objects that contain iron. He wonders whether there is enough iron in a flake of the cereal for it to be attracted by a strong magnet. He thinks that the iron content is probably too low for this to happen, even if he uses a strong magnet. Cody makes an observation that raises a question. Curiosity about observations is how most scientific investigations begin. Q: If Cody were doing a scientific investigation, what would be his question and hypothesis? A: Codys question would be, Is there enough iron in a flake of cereal for it to be attracted by a strong magnet? His hypothesis would be, The iron content of a flake of cereal is too low for it to be attracted by a strong magnet. Q: Based on this evidence, what should Cody conclude? A: Cody should conclude that his hypothesis is incorrect. There is enough iron in a flake of cereal for it to be attracted by a strong magnet. Q: If Cody were a scientist doing an actual scientific investigation, what should he do next? A: He should report his results to other scientists. | text | null |
L_1017 | scientific process | T_4832 | A simple example will help you understand how the scientific method works. While Cody eats a bowl of cereal (Figure 1.2), he reads the ingredients list on the cereal box. He notices that the cereal contains iron. Cody is The general steps followed in the scientific method. studying magnets in school and knows that magnets attract objects that contain iron. He wonders whether there is enough iron in a flake of the cereal for it to be attracted by a strong magnet. He thinks that the iron content is probably too low for this to happen, even if he uses a strong magnet. Cody makes an observation that raises a question. Curiosity about observations is how most scientific investigations begin. Q: If Cody were doing a scientific investigation, what would be his question and hypothesis? A: Codys question would be, Is there enough iron in a flake of cereal for it to be attracted by a strong magnet? His hypothesis would be, The iron content of a flake of cereal is too low for it to be attracted by a strong magnet. Q: Based on this evidence, what should Cody conclude? A: Cody should conclude that his hypothesis is incorrect. There is enough iron in a flake of cereal for it to be attracted by a strong magnet. Q: If Cody were a scientist doing an actual scientific investigation, what should he do next? A: He should report his results to other scientists. | text | null |
L_1018 | scientific theory | T_4833 | The term theory is used differently in science than it is used in everyday language. A scientific theory is a broad explanation that is widely accepted because it is supported by a great deal of evidence. Because it is so well supported, a scientific theory has a very good chance of being a correct explanation for events in nature. Because it is a broad explanation, it can explain many observations and pieces of evidence. In other words, it can help connect and make sense of many phenomena in the natural world. | text | null |
L_1018 | scientific theory | T_4834 | A number of theories in science were first proposed many decades or even centuries ago, but they have withstood the test of time. An example of a physical science theory that has mainly withstood the test of time is Daltons atomic theory. John Dalton was a British chemist who lived in the late 1700s and early 1800s. Around 1800, he published his atomic theory, which is one of the most important theories in science. According to Daltons atomic theory, all substances consist of tiny particles called atoms. Furthermore, all the atoms of a given element are identical, whereas the atoms of different elements are always different. These parts of Daltons atomic theory are still accepted today, although some other details of his theory have since been disproven. Dalton based his theory on many pieces of evidence. For example, he studied many substances called compounds. These are substances that consist of two or more different elements. Dalton determined that a given compound always consists of the same elements in exactly the same proportions, no matter how small the sample of the compound. This idea is illustrated for the compound water in the Figure 1.1. Dalton concluded from this evidence that elements must be made up of tiny particles in order to always combine in the same specific proportions in any given compound. Water is a compound that consists of the elements hydrogen (H) and oxygen (O). Like other compounds, the smallest particles of water are called molecules. Each molecule of water (H2 O) contains two atoms of hydrogen and one atom of oxygen. Q: Dalton thought that atoms are the smallest particles of matter. Scientists now know that atoms are composed of even smaller particles. Does this mean that the rest of Daltons atomic theory should be thrown out? A: The discovery of particles smaller than atoms doesnt mean that we should scrap the entire theory. Atoms are still known to be the smallest particles of elements that have the properties of the elements. Also, it is atomsnot particles of atomsthat combine in fixed proportions in compounds. Instead of throwing out Daltons theory, scientists have refined and expanded on it. There are many other important physical science theories. Here are three more examples: Einsteins theory of gravity Kinetic theory of matter Wave-particle theory of light | text | null |
L_1018 | scientific theory | T_4835 | The formation of scientific theories is generally guided by the law of parsimony. The word parsimony means thriftiness. The law of parsimony states that, when choosing between competing theories, you should select the theory that makes the fewest assumptions. In other words, the simpler theory is more likely to be correct. For example, you probably know that Earth and the other planets of our solar system orbit around the sun. But several centuries ago, it was believed that Earth is at the center of the solar system and the other planets orbit around Earth. While it is possible to explain the movement of planets according to this theory, the explanation is unnecessarily complex. Q: Why do you think parsimony is an important characteristic of scientific theories? A: The more assumptions that must be made to form a scientific theory, the more chances there are for the theory to be incorrect. If one assumption is wrong, so is the theory. Conversely, the theory that makes the fewest assumptions, assuming it is well supported by evidence, is most likely to be correct. | text | null |
L_1020 | scope of physical science | T_4838 | Physical science is the study of matter and energy. That covers a lot of territory because matter refers to all the stuff that exists in the universe. It includes everything you can see and many things that you cannot see, including the air around you. Energy is also universal. Its what gives matter the ability to move and change. Electricity, heat, and light are some of the forms that energy can take. | text | null |
L_1020 | scope of physical science | T_4839 | Physical science, in turn, can be divided into chemistry and physics. Chemistry is the study of matter and energy at the scale of atoms and molecules. For example, the synthetic fibers in the swimmers suit were created in labs by chemists. Physics is the study of matter and energy at all scalesfrom the tiniest particles of matter to the entire universe. Knowledge of several important physics conceptssuch as motion and forcescontributed to the design of the swimmers suit. Q: Its not just athletes that depend on physical science. We all do. What might be some ways that physical science influences our lives? A: We depend on physical science for just about everything that makes modern life possible. You couldnt turn on a light, make a phone call, or use a computer without centuries of discoveries in chemistry and physics. The Figure matter makes each action possible. Each of these pictures represents a way that physical science influences our lives. | text | null |
L_1043 | technological design process | T_4908 | The process in which tri-ATHLETE was created and perfected is called technological design. This is the process in which most new technologies are developed. Technological design is similar to scientific investigation. Both processes rely on evidence and reason, and follow a logical sequence of steps to solve problems or answer questions. The process of designing a new technology includes much more than just coming up with a good idea. Possible limitations, or constraints, on the design must be taken into account. These might include factors such as the cost or safety of the new product or process. Making and testing a model of the design are also important. These steps ensure that the design actually works to solve the problem. This process also gives the designer a chance to find problems and modify the design if necessary. No solution is perfect, but testing and refining a design assures that the technology will provide a workable solution to the problem it is intended to solve. | text | null |
L_1043 | technological design process | T_4909 | The technological design process can be broken down into the series of steps shown in the flowchart in Figure 1.1. Typically, some of the steps have to be repeated, and the steps may not always be done in the sequence shown. This flowchart illustrates the steps of the technological design process. Consider the problem of developing a solar-powered car. Many questions would have to be researched in the design process. For example, what is the best shape for gathering the suns rays? How will sunlight be converted to useable energy to run the car? Will a back-up energy source be needed? After researching the answers, possible designs are developed. This generally takes imagination as well as sound reasoning. Then a model must be designed and tested. This allows any problems with the design to be worked out before a final design is selected and produced. Q: Assume you want to design a product that lets a person in a wheelchair carry around small personal items so they are easy to access. What questions might you research first? A: You might research questions such as: What personal items are people likely to need to carry with them? What types of carriers or holders are there that might be modified for use by people in a wheelchair? Where might a carrier be attached to a wheelchair or person in a wheelchair without interfering with the operation of the chair or hindering the person? Q: Suppose you have come up with a possible solution to the problem described in the previous question. How might you make a model of your idea? How could you test your model? A: First, you might make a sketch of your idea. Then you could make an inexpensive model using simple materials such as cardboard, newspaper, tape, or string. You could test your model by trying to carry several personal items in it while maneuvering around a room in a wheelchair. You would also want to make sure that you could do things like open doors, turn on light switches, and get in and out of the chair without the carrier getting in the way. | text | null |
L_1044 | technology and science | T_4910 | The Hubble space telescope shows that technology and science are closely related. Technology uses science to solve problems, and science uses technology to make new discoveries. However, technology and science have different goals. The goal of science is to answer questions and increase knowledge. The goal of technology is to find solutions to practical problems. Although they have different goals, science and technology work hand in hand, and each helps the other advance. Scientific knowledge is used to create new technologies such as the space telescope. New technologies often allow scientists to explore nature in new ways. | text | null |
L_1044 | technology and science | T_4911 | The Hubble telescope was put into orbit around Earth in the 1990s, but scientists have been using telescopes to make discoveries for hundreds of years. The first telescope was invented in the early 1600s. The inventor was probably a Dutch lens maker named Hans Lippershey. He and his telescope are pictured in Figure 1.1. Lippershey used scientific knowledge of the properties of light and lenses to design his telescope. Lippersheys new technology quickly spread all over Europe. Almost immediately, the Italian scientist and inventor Galileo started working to improve Lippersheys design. In just two years, Galileo had made a more powerful telescope. It could make very distant objects visible to the human eye. The Figure 1.2 shows Galileo demonstrating his powerful telescope. It appears to be focused on the moon. Galileo started using his telescope to explore the night sky. He soon made some remarkable discoveries. He observed hills and valleys on the moon and spots on the sun. He discovered that Jupiter has moons and that the sun rotates on its axis. With his discoveries, Galileo was able to prove that the sun, not Earth, is at the center of the solar system. This discovery played an important role in the history of science. It led to a scientific revolution that gave birth to modern Western science. And it all began with technology! Galileo is shown here presenting his tele- scope to government leaders. They must have been impressed. They gave him a life-long job as a university professor and doubled his salary. | text | null |
L_1044 | technology and science | T_4911 | The Hubble telescope was put into orbit around Earth in the 1990s, but scientists have been using telescopes to make discoveries for hundreds of years. The first telescope was invented in the early 1600s. The inventor was probably a Dutch lens maker named Hans Lippershey. He and his telescope are pictured in Figure 1.1. Lippershey used scientific knowledge of the properties of light and lenses to design his telescope. Lippersheys new technology quickly spread all over Europe. Almost immediately, the Italian scientist and inventor Galileo started working to improve Lippersheys design. In just two years, Galileo had made a more powerful telescope. It could make very distant objects visible to the human eye. The Figure 1.2 shows Galileo demonstrating his powerful telescope. It appears to be focused on the moon. Galileo started using his telescope to explore the night sky. He soon made some remarkable discoveries. He observed hills and valleys on the moon and spots on the sun. He discovered that Jupiter has moons and that the sun rotates on its axis. With his discoveries, Galileo was able to prove that the sun, not Earth, is at the center of the solar system. This discovery played an important role in the history of science. It led to a scientific revolution that gave birth to modern Western science. And it all began with technology! Galileo is shown here presenting his tele- scope to government leaders. They must have been impressed. They gave him a life-long job as a university professor and doubled his salary. | text | null |
L_1044 | technology and science | T_4912 | There are many other examples that show how technology and science work together. Two are pictured in Figure Like the invention of the telescope, the invention of the microscope also depended on scientific knowledge of light and lenses. Q: How do you think the invention of the microscope helped science advance? A: The microscope let scientists view a world of tiny objects they had never seen before. It led to many important scientific discoveries, including the discovery of cells, which are the basic building blocks of all living things. Seismometers and spectrometers are both technological devices that led to im- portant scientific discoveries. | text | null |
L_1046 | technology careers | T_4915 | Companies that design and build roller coasters employ a range of technology professionals. Technology is the application of science to real-world problems. Professionals in technology are generally called engineers. Engineers are creative problem solvers. They use math and science to design and develop just about everythingfrom roller coasters to video games. Q: Whether engineers are designing and developing roller coasters or video games, they need many of the same skills and the same basic knowledge. What skills and knowledge do you think all engineers might need? A: All engineers need basic knowledge of math and science, particularly physical science. For example, to design and build a roller coaster, they would need to know about geometry, as well as forces and motion, which are important topics in physical science. In addition, all engineers must have skills such as logical thinking and creativity. The ability to envision three-dimensional structures from two-dimensional drawings is also helpful for most engineers. | text | null |
L_1046 | technology careers | T_4916 | Different types of engineers, such as electrical and mechanical engineers, must work together to build roller coasters and most other engineering projects. You can learn about these and other technology careers at the URLs listed here and in the Figure 1.1. These are just a few of many possible careers in technology. Do any of these careers interest you? | text | null |
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