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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 |
L_1075 | women and people of color in science | T_5012 | Dr. Ochoa is one of just a few dozen female astronauts in the U.S. She is also the first Hispanic woman in the world to go into space. Although females make up more than half of the U.S. population, fewer than 25 percent of U.S. astronauts are women. Women are also under-represented in science, especially physical sciences such as chemistry and physics. What explains this? Throughout history, womenand also people of color of both gendershave rarely had the same chances as white males for education and careers in science. Cultural, social, and economic biases have made it far harder for them than for white males to excel in this area. This explains why there have been fewer scientists among their ranks. | text | null |
L_1075 | women and people of color in science | T_5013 | Despite their relative lack of opportunities, women and people of color have made many important contributions to science. Several have won Nobel prizes for their discoveries. Just a few of their contributions to physical science are presented in Table 1.1. Scientist Marie Curie (1867-1934) Contribution Marie Curie was the first woman to win a Nobel prizeand she won two of them! She won the 1903 Nobel prize for physics for her discovery of radiation. She won the 1911 Nobel prize for chemistry for her discovery of the elements radium and polonium. C. V. Raman (1888-1970) C. V. Raman was an Indian scientist who won the 1930 Nobel prize for physics. He made important discoveries about how light travels through transparent materials. He was also made a knight of the British Empire for his work. Maria Goeppert-Mayer (1906-1972) Maria Goeppert-Mayer was a German-born American scientist who won the 1963 Nobel prize for physics. She helped to develop a new model of the nucleus of the atom. She was just the second woman to win a Nobel prize for physics, after Marie Curie. Ada E. Yonath (1939-present) Ada E. Yonath was a co-winner of the 2009 Nobel prize in chemistry. She made important discoveries about ribosomes, the structures in living cells where proteins are made. Scientist Mario Molina (1943-present) Contribution Mario Molina is a Mexican-born scientist who won the 1995 Nobel prize for chemistry. He helped to discover how the ozone layer in the atmosphere is being destroyed by pollution. He has received more than 18 honorary degrees for his contributions and even has an asteroid named after him. | text | null |
L_0002 | earth science and its branches | T_0016 | FIGURE 1.11 (A) Mineralogists focus on all kinds of minerals. (B) Seismographs are used to measure earthquakes and pinpoint their origins. | image | textbook_images/earth_science_and_its_branches_20011.png |
L_0002 | earth science and its branches | T_0017 | FIGURE 1.12 These folded rock layers have bent over time. Studying rock layers helps scientists to explain these layers and the geologic history of the area. | image | textbook_images/earth_science_and_its_branches_20012.png |
L_0002 | earth science and its branches | T_0017 | FIGURE 1.13 This research vessel is specially designed to explore the seas around Antarctica. | image | textbook_images/earth_science_and_its_branches_20013.png |
L_0002 | earth science and its branches | T_0018 | FIGURE 1.14 Meteorologists can help us to prepare for major storms or know if today is a good day for a picnic. | image | textbook_images/earth_science_and_its_branches_20014.png |
L_0002 | earth science and its branches | T_0018 | FIGURE 1.15 Carbon dioxide released into the atmo- sphere is causing global warming. | image | textbook_images/earth_science_and_its_branches_20015.png |
L_0002 | earth science and its branches | T_0019 | FIGURE 1.16 In a marine ecosystem, coral, fish, and other sea life depend on each other for survival. | image | textbook_images/earth_science_and_its_branches_20016.png |
L_0003 | erosion and deposition by flowing water | T_0021 | FIGURE 10.1 Flowing water erodes or deposits parti- cles depending on how fast the water is moving and how big the particles are. | image | textbook_images/erosion_and_deposition_by_flowing_water_20018.png |
L_0003 | erosion and deposition by flowing water | T_0023 | FIGURE 10.2 How Flowing Water Moves Particles. How particles are moved by flowing water de- pends on their size. | image | textbook_images/erosion_and_deposition_by_flowing_water_20019.png |
L_0003 | erosion and deposition by flowing water | T_0027 | FIGURE 10.3 Erosion by Runoff. Runoff has eroded small channels through this bare field. | image | textbook_images/erosion_and_deposition_by_flowing_water_20020.png |
L_0003 | erosion and deposition by flowing water | T_0027 | FIGURE 10.4 Mountain Stream. This mountain stream races down a steep slope. | image | textbook_images/erosion_and_deposition_by_flowing_water_20021.png |
L_0003 | erosion and deposition by flowing water | T_0029 | FIGURE 10.5 How a Waterfall Forms and Moves. Why does a waterfall keep moving upstream? | image | textbook_images/erosion_and_deposition_by_flowing_water_20022.png |
L_0003 | erosion and deposition by flowing water | T_0029 | FIGURE 10.6 Meanders form because water erodes the outside of curves and deposits eroded material on the inside. Over time, the curves shift position. | image | textbook_images/erosion_and_deposition_by_flowing_water_20023.png |
L_0003 | erosion and deposition by flowing water | T_0030 | FIGURE 10.7 An alluvial fan in Death Valley, California (left), Nile River Delta in Egypt (right). | image | textbook_images/erosion_and_deposition_by_flowing_water_20024.png |
L_0003 | erosion and deposition by flowing water | T_0032 | FIGURE 10.8 This diagram shows how a river builds natural levees along its banks. | image | textbook_images/erosion_and_deposition_by_flowing_water_20025.png |
L_0003 | erosion and deposition by flowing water | T_0033 | FIGURE 10.9 This cave has both stalactites and stalag- mites. | image | textbook_images/erosion_and_deposition_by_flowing_water_20026.png |
L_0003 | erosion and deposition by flowing water | T_0034 | FIGURE 10.10 A sinkhole. | image | textbook_images/erosion_and_deposition_by_flowing_water_20027.png |
L_0003 | erosion and deposition by flowing water | DD_0001 | The diagram represents the coastal Erosion of a headland. A headland is an area of hard rock which sticks out into the sea. Headlands form in areas of alternating hard and soft rock. Where the soft rock erodes, bays are formed on either side of the headland. As the headland becomes more exposed to the wind and waves the rate of its erosion increases. When headlands erode they create distinct features such as caves, arches, stacks and stumps. The sequence in the erosion of a headland is as follows : 1. Waves attack a weakness in the headland. 2. A cave is formed. 3. Eventually the cave erodes through the headland to form an arch. 4. The roof of the arch collapses leaving a column of rock called a stack. 5. The stack collapses leaving a stump. | image | teaching_images/erosion_6859.png |
L_0003 | erosion and deposition by flowing water | DD_0002 | The diagram shows how a waterfall is formed by erosion. Waterfalls begin with mountain streams that begin high up in mountains. These streams flow down very quickly because of the steep slope, and flowing water, especially fast-moving water, erodes soil and rocks. Soft rock erodes more quickly than hard rock. When soft rock erodes, the stream bed can collapse, causing an abrupt drop in the stream. This sudden drop is what creates a waterfall. In the diagram, the overhang is where the stream bed collapsed to create the waterfall. Because of the flowing water, the soft rock at the side of the waterfall will continue to erode. This continued erosion will cause more of the stream bed to collapse. The waterfall overhang will then retreat upstream and create a higher waterfall. | image | teaching_images/erosion_8064.png |
L_0004 | erosion and deposition by waves | T_0035 | FIGURE 10.11 Ocean waves transfer energy from the wind through the water. This gives waves the energy to erode the shore. | image | textbook_images/erosion_and_deposition_by_waves_20028.png |
L_0004 | erosion and deposition by waves | T_0037 | FIGURE 10.12 Over millions of years, wave erosion can create wave-cut cliffs (A), sea arches (B), or sea stacks (C). | image | textbook_images/erosion_and_deposition_by_waves_20029.png |
L_0004 | erosion and deposition by waves | T_0039 | FIGURE 10.13 Sand deposited along a shoreline creates a beach. | image | textbook_images/erosion_and_deposition_by_waves_20030.png |
L_0004 | erosion and deposition by waves | T_0039 | FIGURE 10.14 Beach deposits usually consist of small pieces of rock and shell in addition to sand. | image | textbook_images/erosion_and_deposition_by_waves_20031.png |
L_0004 | erosion and deposition by waves | T_0040 | FIGURE 10.15 Longshore drift carries particles of sand and rock down a coastline. | image | textbook_images/erosion_and_deposition_by_waves_20032.png |
L_0004 | erosion and deposition by waves | T_0041 | FIGURE 10.16 Spit from Space. Farewell Spit in New Zealand is clearly visible from space. This photo was taken by an astronaut orbiting Earth. | image | textbook_images/erosion_and_deposition_by_waves_20033.png |
L_0004 | erosion and deposition by waves | T_0042 | FIGURE 10.17 Wave-Deposited Landforms. These land- forms were deposited by waves. (A) Sandbars connect the small islands on this beach on Thailand. (B) A barrier island is a long, narrow island. It forms when sand is deposited by waves parallel to a coast. It develops from a sandbar that has built up enough to break through the waters surface. A barrier island helps protect the coast from wave erosion. | image | textbook_images/erosion_and_deposition_by_waves_20034.png |
L_0004 | erosion and deposition by waves | T_0043 | FIGURE 10.18 A breakwater is an artificial barrier island. How does it help protect the shoreline? | image | textbook_images/erosion_and_deposition_by_waves_20035.png |
L_0004 | erosion and deposition by waves | T_0044 | FIGURE 10.19 A groin is built perpendicular to the shore- line. Sand collects on the upcurrent side. | image | textbook_images/erosion_and_deposition_by_waves_20036.png |
L_0006 | erosion and deposition by glaciers | T_0054 | FIGURE 10.27 (A) The continent of Antarctica is covered with a continental glacier. (B) A valley glacier in the Canadian Rockies. (C) The surface of a valley glacier. | image | textbook_images/erosion_and_deposition_by_glaciers_20044.png |
L_0006 | erosion and deposition by glaciers | T_0056 | FIGURE 10.28 Features Eroded by Valley Glaciers. Ero- sion by valley glaciers forms the unique features shown here. | image | textbook_images/erosion_and_deposition_by_glaciers_20045.png |
L_0006 | erosion and deposition by glaciers | DD_0003 | This diagram shows about Erosion and Deposition by Glaciers. Glaciers are made up of fallen snow that, over many years, compresses into large, thickened ice masses. Glaciers form when snow remains in one location long enough to transform into ice. What makes glaciers unique is their ability to move. Due to sheer mass, glaciers flow like very slow rivers. Some glaciers are as small as football fields, while others grow to be dozens or even hundreds of kilometers long. Presently, glaciers occupy about 10 percent of the world's total land area, with most located in polar regions like Antarctica, Greenland, and the Canadian Arctic. Most glaciers lie within mountain ranges. Glaciers cause erosion by plucking and abrasion. Glaciers deposit their sediment when they melt. Landforms deposited by glaciers include drumlins, kettle lakes, and eskers. A ground moraine is a thick layer of sediments left behind by a retreating glacier. A drumlin is a long, low hill of sediments deposited by a glacier. Drumlins often occur in groups called drumlin fields. An esker is a winding ridge of sand deposited by a stream of meltwater. A kettle lake occurs where a chunk of ice was left behind in the sediments of a retreating glacier. When the ice melted, it left a depression. The meltwater filled it to form a lake. | image | teaching_images/glaciers_6926.png |
L_0006 | erosion and deposition by glaciers | DD_0004 | The diagram shows several features of an alpine glacier. Glaciers are masses of flowing ice that are formed when more snow falls than melts each year. Snow falls in the accumulation zone, usually the part of the glacier with the highest elevation. Further down the glacier, usually at a lower altitude, is the ablation area, where most of the melting and evaporation occur. At locations where a glacier flows rapidly, friction creates giant cracks called crevasse. Moraines are created when the glacier pushes or carries rocky debris as it moves. Medial moraines run down the middle of a glacier, lateral moraines along the sides, and terminal moraines are found at the terminus of a glacier. Glaciers cause erosion by plucking and abrasion. Valley glaciers form several unique features through erosion, including cirques and artes. Glaciers deposit their sediment when they melt. Landforms deposited by glaciers include drumlins, kettle lakes, and eskers. | image | teaching_images/glaciers_6936.png |
L_0008 | fossils | T_0066 | FIGURE 11.1 A variety of fossil types are pictured here. Preserved Remains: (A) teeth of a cow, (B) nearly complete dinosaur skeleton embedded in rock, (C) sea shell pre- served in a rock. Preserved Traces: (D) dinosaur tracks in mud, (E) fossil animal burrow in rock, (F) fossil feces from a meat-eating dinosaur in Canada. | image | textbook_images/fossils_20051.png |
L_0008 | fossils | T_0066 | FIGURE 11.2 Fossilization. This flowchart shows how most fossils form. | image | textbook_images/fossils_20052.png |
L_0008 | fossils | T_0067 | FIGURE 11.3 Ways Fossils Form. (A) Complete Preser- vation. This spider looks the same as it did the day it died millions of years ago! (B) Molds and Casts. A mold is a hole left in rock after an organisms remains break. A cast forms from the minerals that fill that hole and solidify. (C) Compression. A dark stain is left on a rock that was compressed. These ferns were fossilized by compression. | image | textbook_images/fossils_20053.png |
L_0008 | fossils | T_0070 | FIGURE 11.4 What can we learn from fossil clues like this fish fossil found in the Wyoming desert? | image | textbook_images/fossils_20054.png |
L_0008 | fossils | T_0071 | FIGURE 11.5 Trilobites are good index fossils. Why are trilobite fossils useful as index fossils? | image | textbook_images/fossils_20055.png |
L_0008 | fossils | DD_0005 | The diagram here shows us the stages of fossil creation. The first picture shows a living dinosaur that may have existed a thousand years ago. The second picture shows us dinosaur bones beneath waterbed. The third picture shows the bones separated and within the earth's rocks. And finally the fourth picture shows a man excavating and discovering the dinosaur bones, also known as fossils. Now what exactly are fossils? Fossils are nothing but the remains or impression of a prehistoric plant or animal embedded in rock and preserved in petrified form. The process by which remains or traces of living things become fossils is called fossilization. Most fossils are preserved in sedimentary rocks. Fossils are our best clues about the history of life on Earth. | image | teaching_images/fossils_9105.png |
L_0008 | fossils | DD_0006 | The diagram shows one way that fossils can form. There are 4 main stages. We see it begins when plants and animals die. They sink to the bottom of the sea. The dead animals become covered by sediment. Over time the pressure from the sediment compresses the dead animals into oil. Oil eventually moves up thru rocks. It then forms a reservoir and the process is complete. | image | teaching_images/fossils_6897.png |
L_0009 | relative ages of rocks | T_0073 | FIGURE 11.6 Laws of Stratigraphy. This diagram illus- trates the laws of stratigraphy. A = Law of Superposition, B = Law of Lateral Conti- nuity, C = Law of Original Horizontality, D = Law of Cross-Cutting Relationships | image | textbook_images/relative_ages_of_rocks_20056.png |
L_0009 | relative ages of rocks | T_0073 | FIGURE 11.7 Superposition. The rock layers at the bottom of this cliff are much older than those at the top. What force eroded the rocks and exposed the layers? | image | textbook_images/relative_ages_of_rocks_20057.png |
L_0009 | relative ages of rocks | T_0074 | FIGURE 11.8 Lateral Continuity. Layers of the same rock type are found across canyons at the Grand Canyon. | image | textbook_images/relative_ages_of_rocks_20058.png |
L_0009 | relative ages of rocks | T_0077 | FIGURE 11.9 Cross-cutting relationships in rock layers. Rock D is a dike that cuts across all the other rocks. Is it older or younger than the other rocks? | image | textbook_images/relative_ages_of_rocks_20060.png |
L_0009 | relative ages of rocks | T_0077 | FIGURE 11.10 Huttons unconformity, in Scotland. | image | textbook_images/relative_ages_of_rocks_20059.png |
L_0009 | relative ages of rocks | T_0079 | FIGURE 11.11 Chalk Cliffs. (A) Matching chalk cliffs in Denmark and (B) in Dover, U.K. | image | textbook_images/relative_ages_of_rocks_20061.png |
L_0009 | relative ages of rocks | T_0081 | FIGURE 11.12 Using Index Fossils to Match Rock Lay- ers. Rock layers with the same index fossils must have formed at about the same time. The presence of more than one type of index fossil provides stronger evidence that rock layers are the same age. | image | textbook_images/relative_ages_of_rocks_20062.png |
L_0009 | relative ages of rocks | T_0085 | FIGURE 11.13 The Geologic Time Scale. | image | textbook_images/relative_ages_of_rocks_20063.png |
L_0009 | relative ages of rocks | T_0086 | FIGURE 11.14 The evolution of life is shown on this spi- ral. | image | textbook_images/relative_ages_of_rocks_20064.png |
L_0009 | relative ages of rocks | DD_0007 | This diagram represents the cross-cutting relationships of rocks. Layer 1, as shown, is the oldest layer because it is the layer that is the deepest. This is the law of superposition. In the diagram below, "dike" is the youngest rock layer. This is figured by the law of cross-cutting relationships. The layers are always older than the rock that cuts across them. In the diagram below, dike cuts through all four layers. Therefore, layer 1 is the oldest, layer 2 is the second oldest, layer 3 is the third oldest, layer 4 is the fourth oldest, and dike is the youngest layer of rock. | image | teaching_images/stratigraphy_9259.png |
L_0009 | relative ages of rocks | DD_0008 | The study of rock strata is called stratigraphy. This Diagram is all about the Laws of Stratigraphy. The laws of stratigraphy can help scientists understand Earths past. The relative ages of rocks are important for understanding Earths history. The diagram refers to the position of rock layers and their relative ages, which is called Superposition. New rock layers are always deposited on top of existing rock layers. Therefore, deeper layers must be older than layers closer to the surface. A is the area covered by Law of Cross-Cutting relationships, B is the unconformities, C is the law of Original Horizontality, D is the Law of Conti-unity, E is the law of Superposition. Some rock layers extend over a very wide area. They may be found on more than one continent or in more than one country. | image | teaching_images/stratigraphy_9262.png |
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