HIGH SCHOOL SCIENCE. The Practice of Science

Transcription

1 HIGH SCHOOL SCIENCE The Practice of Science WILLMAR PUBLIC SCHOOL EDITION

2 CHAPTER 1 Practice of Science In this chapter you will: 1.understand what science is and how it obtains knowledge 2.understand how scientist conduct an investigation 3.understand the connections between science and technology

3 CHAPTER 1 SECTION 1 What is Science? OBJECTIVES 1. Describe how science gains knowledge. 2. Identify and describe what is studied in science. Vocabulary: science specialization life science Earth and space science physical science Science is a way of knowing about the natural world. It is a way of finding out why things happen they way they do. Science uses observations, a system of methods, and logical reasoning to discover that knowledge. Scientists try to solve problems by testing possible answers to see if they work. Science knowledge is based on observations, questioning, and testing. As people learn more about the world, they choose more specific subjects to study or specialize. Specialization is studying or working in only one part of a subject. A person who studies or works in one part of a subject is called a specialist. How many different sciences careers can you name? Your list would probably include doctor, engineer, astronaut, veterinarian, and park ranger. But it could also include bacteriologist (a person who studies bacteria), ornithologist (a person who studies birds), seismologist (a person who studies earthquakes), and thermodynamicist (a person who studies the physics of heat & energy). Science spans many diverse fields and interests. Because the areas of scientific study are so diverse, scientists organize their work into three major branches of study. The three main branches of natural science are life 2

4 science, Earth and space science, and physical science. Life Science NATURAL SCIENCE Earth & Space Science Physical Science Botany Geology Physics Ecology Oceanography Chemistry Zoology Genetics Meteorology Astronomy Life science, or biology, is the study of living things. Life scientists study how living things interact with each other and with their surroundings. It is divided into many different branches that includes plants, animals, and microscopic life forms. The study of living things affects your life in many ways. Some of the foods you eat are produced using information about how plants grow, using knowledge of the activities of insects, and using the knowledge of molds and bacterias. Many plants have been genetically modified to grow bigger and faster. Crime lab technicians work with different kinds of evidence. Evidence may include cloth, fibers, bits of paper, hair, skin and blood. Earth and the processes that shape the Earth. Besides geology, Earth and space science includes oceanography, meteorology, and astronomy. The scientific study of the sea is called oceanography. In order to study the ocean, oceanographers not only study the ocean from its surface, but also in miniature research submarines. These submarines can go practically anywhere in the ocean. Meteorology is the study of weather and climate. It is important to understand the weather so you can be predict and be safe during a storm. Astronomy is the study of space. Understanding space helps us understand our Earth better. If we understand Mars, then we can compare and contrast to our Earth. The last branch of natural science is physical science. Physical science is the study of non-living things. The two main areas of physical science are chemistry and physics. Chemistry is the study of the composition, structure, properties, and reactions of matter. Physics is the study of matter and energy and the interactions between the two through forces and motion. Although it is convenient to think of science as divided into three branches, these areas are not really separate at all. Most scientific questions being investigated today span the different fields of science. Also, in many non-science areas, a knowledge of science is essential in order to perform the job. Earth and space science is the study of Earth and its place in the universe. The foundation of Earth science is geology. Geology is the study of the origin, history, and structure of 3

5 Section Review: 1. How do scientists gain knowledge? 2.Why do scientist specialize? 3.What are the three branches of natural science? 4.Into which branch of science would you classify the following: a scientist studying the organisms in a river? 5. How do the different branches of science depend on one another? 6.How do you think a knowledge of science would benefit a chef? 4

6 CHAPTER 1 SECTION 2 Scientific Method OBJECTIVES 1. Explain the steps of the scientific method. People have a strong sense of curiosity. Curiosity provides problems or questions about observations that leads to scientific inquiry. In order to solve the problem or answer the questions about the world around them, scientists need to gather information. An organized plan for gathering, organizing, and communicating information is called scientific method. The goal of the scientific method is to solve a problem or to better understand an observed event. 2. Compare the differences between hypothesis, scientific theory, and scientific law. Vocabulary: scientific method observation hypothesis variable independent variable dependent variable control experiment analyzing scientific theory scientific law Scientific inquiry begin with observations. An observation is information obtained through your senses. Your senses include sight, hearing, touch, taste, and smell. Observations can be either quantitative or qualitative. Quantitative observations deal with a number, or amount. Qualitative 5

7 observations deal with descriptions that cannot be expressed in numbers. From the observations, a question or problem can be developed. Some problems or questions cannot be investigated by scientific inquiry. If you had a question about why a mp3 player stopped working, that would be a scientific questions; however, if you were wondering what kind of music to play, that would not be a scientific question. In trying to answer a question, you are in fact developing a hypothesis. A hypothesis is a possible explanation or proposed answer to a question. It is important to remember that a hypothesis is not a fact. Repeatable observations are known as facts. Instead a hypothesis is only one possible way to explain a group of observations. In science, a hypothesis must be testable. Scientists perform experiments to test their hypothesis. In an experiment, any factor that can change is called a variable. One variable that is purposely changed to test the hypothesis, or the variable that causes a change in another, is called the independent variable. The variable that may change in response to the independent variable is the dependent variable. To examine the relationship between a independent variable and the dependent variable, scientists use controlled experiments. A controlled experiment is an experiment which only one independent variable is deliberately changed at a time. While the dependent variable is observed for changes, all other variables are kept constant or controlled. As the hypothesis is being tested, data is being collected. Data is the recorded facts, figures, measurements, or other evidence from an experiment. It is important to organize the data into a data table. A data table helps you organize the information you collect in an experiment so you can analyze it. Analyzing is studying the relationship between the variables. After all the data have been collected, they will need to be interpreted or analyzed. One useful tool that can help you analyze your data is a graph. Now that you have gathered and analyzed your data, you can draw conclusions. First you decide if your hypothesis is supported or not. You should ask yourself whether the data supports your hypothesis. You also need to consider whether you collected enough data and whether anything happened during the experiment that might have affected the results. If your data supports the hypothesis, you should state that the data supports the hypothesis; however, if your data does not support your hypothesis, a new hypothesis may be created. Data should never be revised to fit a hypothesis. An important part of scientific inquiry is communicating your results. Scientists share their ideas in many ways. For example, they give talks at scientific meetings, exchange information on the Internet, or publish articles in scientific journals. 6

8 As a body of knowledge, science is built up cautiously. Scientists do not accept a new hypothesis after just one successful experiment. Rather a hypothesis is tested repeatedly as many different scientists try to apply it to their own work. Once a hypothesis has been supported in repeated experiments, scientists can begin to develop a theory. A scientific theory is a hypothesis that has been tested again and again by many scientists, with similar results each time. A scientific theory is not a guess. It is the best explanation science has to offer about a problem. Theories are never proved, but become stronger and stronger if the facts continue to support them. However, if an existing their fails to explain new facts, the theory may be revised or a new theory may replace it. A scientific law is a statement that describes what scientists expect to happen every time under a particular set of conditions. Unlike a theory, a scientific law describes an observed patter in nature without attempting to explain it. Section Review: 1. What is the goal of the scientific method? 2.What are the variables in a controlled experiment? 3.Every time you and your friend study for an exam while listening to classical music, both of you do well on the exam. What testable hypothesis can you develop from your observations? 4.What steps of the scientific method should be done before performing an experiment? 5. What is one way to help you analyze data? 6.Why is a scientific theory more accepted than a hypothesis? 7. What does a scientific law describe? 8.How do scientific theories differ from scientific laws? 7

9 CHAPTER 1 SECTION 3 Technology & Science When you see or hear the word technology, you may think of things such as ipads, mp3 players, and cellphones. But technology includes more than modern inventions. Ancient inventions, such as stone tools, the wheel, and the compass, are examples of technology too. Technology has been around since people started to make things to suit their needs. As scientific knowledge is discovered, it can be applied in ways that improve the lives of people. Technology is the use of knowledge to solve practical problems. While the goal of science is to expand knowledge, the goal of technology is to apply that knowledge and improve the way people live. Science and technology are interdependent; advances in one lead to advances in the other. OBJECTIVES 1. Describe technology. 2. Explain the connections between technology and society. 3. Describe the importance of analyze the risks and benefits of technology. Vocabulary: technology risk-benefit analysis In every age of history, technology has had a large impact on society, from the Stone Age thousand years ago to the Information Age today. During the Stone Age, people used stones to make tools. Spears, axes, and spades enabled people to hunt animals and grow crops. During the Iron Age, people produced iron to make weapons and tools, such as chisels, saws, water wheels, and grain mills. Today, in the Information Age, people use electronic devices to share information quickly around the world. In addition to positive effects, technology can have negative consequences. Technological advances make many jobs easier to perform; however, the advance in technology can cause people to lose their jobs. In deciding whether to use a particular technology, people must analyze its possible risks 8

10 and benefits. The process of risk-benefit analysis involves evaluating the possible problems, or risks, of a technology compared to the expected advantages, or benefits. In evaluating a technology s risks and benefits, individuals and societies must consider human values. A value is something that a person or society regards as important, such as health, honesty, convenience, and personal freedom. Difficulties can arise when values conflict - when one value favors a technology while another value cautions against it. Section Review: 1. What is the goal of technology? 2.How does technology differ from science? 3.How has technology impact society? 4.List one example of technology that has increased the pace of your life. What positives and negatives impact has this technology had? 5. Why is it important to analyze the risks and benefits of technology? 9

11 CHAPTER 1 SECTION 4 Mathematics & Science OBJECTIVE 1. Explain how math skills help scientists analyze their data. Vocabulary: estimate mean median mode accuracy precision significant figures scientific notation percent error You might think that mathematics as something that is separate from science; however, it is not. Mathematics is sometimes called the language of science. Mathematics is essential for asking and answering questions about the natural world. From making measurements to collecting and analyzing data, scientists use math every day. Scientists must sometimes rely on estimates when they cannot obtain exact numbers. An estimate is an approximation of a number based on reasonable assumptions. Estimating is not the same as guessing because an estimate is based on known information. Astronomers can t actually measure the distance between stars. Park ranges can t count the number of trees in large forests. Instead, scientists fond ways to make reasonable estimates like using indirect measurements. There are several ways to determine an average. They include the mean, median, and mode. The mean is calculated by adding up all the numbers and then dividing by the total number of items in the list. Mean = (Sum of Values) / (Total # of Values) Median is the middle number of a set of data. To find the median, place all the numbers in order from smallest to largest. If the order list has an odd number of entries, the median is the middle entry. If the list has an even number of entries, you add the two middle numbers together and divide by two. Mode is the number that appears most often in a list of numbers. 10

12 Both accuracy and precision are important when you make measurements. Accuracy is the closeness of a measurement to the actual value of what is being measured. If you think of a target, accuracy is how close to the bull s eye the shots are located. Precision is how close a group of measurement are to each other or how exact a measurement is. On the target, precision is how close together the shots are located. You can determine the number of significant figures in a number using a few simple rules. All non-zero numbers are significant. (472 has three significant figures, has four significant figures) Zeroes between significant digits are significant. (103 has three significant figures, has five significant figures) If there is no decimal point, then trailing zeroes are not significant. (81000 has two significant figures, has three significant figures) If there is a decimal point, then all trailing zeroes are significant. ( has five significant figures, 10. has two significant figures) If a number is less than one, then the first significant figure is the first non-zero digit after the decimal point. (0.004 has one significant figure, has three significant figures) Whenever you measure something, you give meaning to each digit in the measurement. Significant figures refer to the digits in a measurement. Significant figures in a measurement include all the digits that have been measured exactly, plus one digit whose value has been estimated. Scientist often work with very large or very small numbers. For example, the speed of light is about 300,000,000 m/s and the speed of an average snail is about m/s. Instead of writing out all the zeros, scientists use scientific notation. Scientific notation is a way to express numbers in terms of a decimal number between 1 and 10 multiplied by a power of ten. For example, the speed of light would be expressed as 3.0 x 10 8 and the snail speed would be expressed as 9.84 x A positive exponent tells the decimal is really that number places to the right of the decimal point. A negative exponent 11

13 tells the decimal is really that number places to the left of the decimal point. If you were to take and express it as in scientific notation, first take the first integer (between 0 and 10). Add the decimal and the rest of the significant numbers. Then add time ten to the power of the number and direction the decimal moved. So would be 9.085x10 6. The precision of a calculated answer is limited by the measurement with the least significant figures used in the calculation. When you add or subtract measurements, the answer can only have as many figures after the decimal point as the measurement with the fewest figures after the decimal. For example, 9.2 m m = 62.6 m because the measurement 9.2 meters only has one point after the decimal. When multiplying or dividing, you need to follow a slightly different rule; the answer can only have the same number of significant figures as the measurement with the fewest significant figures. For example, 6.2 cm x 312 cm = 1900 cm 2 because 6.2 cm has two significant figures. Section Review: 1. What are estimates based on? 2.What are the three ways of calculating an average? 3.Why is it important to obtain measurements that are both accurate and precise? 4.How many significant figures does have? 5. Why do scientists use scientific notation? 6.How does the precision of measurements affect the precision of scientific calculations? 7. What is the rule for multiplying or dividing measurements? Percent error calculations are used to determine how accurate, or close to the true value, an experimental value really is. To calculate percent error divide the difference between the measured value and accepted value with the accepted value then times by 100%. 12

14 CHAPTER 1 SECTION 5 Measurement OBJECTIVES 1. Describe why scientists use a standard measurement system. 2. Describe the tools used to measure length, volume, mass, time, and temperature. 3. Identify the SI units for length, volume, mass, time, and temperature. Vocabulary: measurement Measurement is the system of comparing an object to a standard. The metric system includes units of length (meters), weight or mass (grams), and volume (liter). When we make a measurement of length, weight, or volume, we are comparing the object against a standard (1 meter, 1 gram, 1 volume). Tools for metric measurements provide these standards. Using the same system of measurement minimizes confusion among scientists all over the world. More than 200 years ago, most countries used their own measurement systems. In the 1790 s, scientists in France developed a universal system of measurement called the metric system. The metric system is a system of measurement based on the number ten. Modern scientists use a version of the metric system call the International System of Units, abbreviated SI. Using SI as the standard system of measurement allows scientists to compare data and communicate with each other about their results. length volume water displacement mass weight time temperature Length is the distance from one point to another. The metric ruler is the tool for measuring length, and width. It looks like any other kind of ruler but includes units of millimeters, centimeters, and meters. The SI unit for length is the meter. You can also determine the volume of a rectangular solid using a ruler. Volume is the amount of space an object takes up. Volume = length x width x height. The SI unit for volume is the cubic meter (m 3 ); however, in science class you will be 13

15 using the cubic centimeter (cm 3 ). The unit you would use is the cubic centimeter, one cubic centimeter equals to one milliliter. standard weights of milligrams, centigrams, and kilograms comprise the other half. The SI units for mass is kilogram; however, in science class you will be using the gram. When the weight of the object being measured equals the combination of standard weights the scale balances. A graduated cylinder measures volume of a liquid. It looks like a drinking glass that has marks for volume on the side milliliters, centiliters, and liters. Suppose you wanted to measure the volume of a rock. Because of its irregular shape, you cannot measure the rock s length, width, or height. You would then use a graduated cylinder and immerse the rock in water. Then you would measure how much the water level rises, this method is called water displacement. The balance or scale is the appropriate tool for measuring mass or weight in grams. Mass is how much matter is in something. Weight is a measurement of the force of gravity on an object. The balance looks something like a seesaw. With the object being measured on one side, a combination of A stopwatch or a clock with a second hand is used to measure time. Time is the period between two events. The SI unit for time is the second. A thermometer is used to measure temperature. Temperature is a measurement of the amount of heat in something. The SI unit for temperature is the kelvin. Scientists frequently measure temperature with Celsius scale. A temperature of 0 kelvin (K), refers to the lowest possible temperature that can be reached. In degrees Celsius, this temperature is degrees Celsius. Kelvins equal degrees Celsius plus On the Celsius scale, the freezing point of water is 0 degrees and the boiling point is 100 degrees. 14

16 Section Review: 1. Why do scientists use a standard measurement system? 2.What is the standard measurement system used by scientists around the world? 3.Suppose that two scientists use different measurement systems in their work. What problems might arise if they shared their data? 4.List the SI units for length, volume, mass, time and temperature. 5. What is the difference between weight and mass? 6.What tool should you use to measure the volume of water? 15

17 CHAPTER 1 SECTION 6 Organizing Data OBJECTIVE 1. Identify how scientists organize data. 2. Describe the uses of different graphs. 3. Understand the different types of trends shown on a graph. 4. Calculate slope on a linear graph. Vocabulary: data table graph line graph bar graph circle graph pictograph linear trend slope nonlinear trend Scientists accumulate vast amounts of data by observing and making measurements. Scientists organize their data by using data tables and graphs. Data is facts, figures, and other evidence gathered through observations. A data table provides you with an organized way to collect and record your observations, or data. After all your data have been collected, they need to be interpreted. One useful tool that can help you interpret data is graph. A graph is a visual representation of a set of data. Think of graphs as pictures of the data. Graphs an reveal patterns or trends in data by seeing similarities. There are four types of graphs that are commonly used: line graph, bar graph, circle, and pictograph. A line graph is used for showing changes that occur in related variables. They display data to show how the dependent variable changes in response to the independent variable. The horizontal axis, or x-axis, shows the range of the independent variable. The vertical axis, or y-axis, shows the range of the dependent variable. A bar graph is often used to compare a set of measurements, amounts, or changes. A bar graph is similar to a line graph except bars rather than points show the data. In a bar graph, the dependent variable can be shown on either the vertical or horizontal axes. A circle graph, or pie graph, is a divided circle that shows a parts of a whole. The size of each section shows a percentage of the whole circle. If you add the percentages of the sections together, they equal 100 percent. 16

18 A pictograph is is a graph using pictures. It can be like a circle graph by showing parts of a whole or use symbols to represent a number of something. Graphs allow you to identify trends and make predictions. There are three trends: linear, nonlinear, and no trend. A linear trend is a graph with a straight line. When a graph is linear, you can easily see how two variables are related. If the data yields linear trend, you can determine a value called slope. Slope is the steepness or ratio of the vertical change to horizontal change. Slope (m) is calculated using the formula: Section Review: 1. What can graphs reveal that data tables cannot? 2.What type of data can line graphs display? 3.How do you determine the slope of a line? 4.If the rise is 16 and the run is 4, what is the slope of the line? 5. Why are graphs powerful tools in science? 6.Describe a nonlinear graph. Rise represents the change in the dependent variable. Run represents the change in the independent variable. You can use a linear graph to make predictions by extending the line. A nonlinear trend show different trends. One nonlinear graph the points may fall along a curve. A graph may rise then level off or have a repeating pattern. Lastly, data may scatter and show no recognizable pattern which would be no trend. When there is no identifiable trends in a graph, it most likely means that there is no relationship between the two variables. 17

19 CHAPTER 1 SECTION 7 Safety in the Lab Research in science can be exciting, but it also has potential dangers. For example, a field scientist could collect a water samples from a polluted lake. There are many microorganisms in the water that could make her sick. The water and shore are also strewn with dangerous objects such as sharp can lids and broken glass bottles that could cause serious injury. Whether in the field or in the lab, knowing how to stay safe in science is important. 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. Lab safety symbols warn of specific hazards, such as flames or broken glass. Knowing the symbols allows you to recognize and avoid the dangers. OBJECTIVES 1. Describe the importance of being safe in the lab. 2. Understand how to react in an accident. Vocabulary: safety symbols safe practices 18

20 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. 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. Following basic safety rules, such as wearing safety gear, helps prevent accidents in the lab and in the field. Different rules may apply when you work in the field. But in all cases, you should always follow your teacher s instructions. Lab Safety Rules 1. Wear long sleeves and shoes that completely cover your feet. 2. If your hair is long, tie it back or cover it with a hair net. 3. Protect your eyes, skin, and clothing by wearing safety goggles, an apron, and gloves. 4. Use hot mitts to handle hot objects. 5. Never work in the lab alone. 9. Always add acid to water, never the other way around, and add the acid slowly to avoid splashing. 10.Take care to avoid knocking over Bunsen burners, and keep them away from flammable materials such as paper. 11.Use your hand to fan vapors toward your nose rather than smelling substances directly. 12.Never point the open end of a test tube toward anyone including yourself! 13.Clean up any spills immediately. 14.Dispose of lab wastes according to your teacher s instructions. 15.Wash glassware and counters when you finish your work. 16.Wash your hands with soap and water before leaving the lab. 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. All accidents should be reported immediately. 6. Never engage in horseplay in the lab. 7. Never eat or drink in the lab. 8. Never do experiments without your teacher s approval. 19

21 Section Review: 1. What do the safety symbols describe? 2.If you see a symbol with flames on it, what do you know about that chemical? 3.How should you protect your skin during a lab? 4.If you are using a chemical and it spills, what should you do? 20