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Using the Scientific Method • When you hear or read about advancements in science, do you wonder how they were made? How did the scientists make their discoveries? Were they just lucky? Maybe, but chances are that it was much more than luck. The scientific method probably had a lot to do with it!
What is the Scientific Method? • Thescientific method is a series of steps that scientists use to answer questions and solve problems. The chart below shows the steps that are commonly used in the scientific method. Although the scientific method has several distinct steps, it is not a rigid procedure whose steps must be followed in a certain order. Scientists may use the steps in a different order, skip steps, or repeat steps. It all depends on what works best to answer the question.
MISCONCEPTION ALERT • Scientists approach problems from a variety of viewpoints. They conduct their research using available tools, data, time and people. Research often leads to new problems and new hypotheses, which require further research and testing.
Bell ringer • How can you prove that the world is not flat?
Ask a Question • Asking a question helps you focus your investigation and identify what you want to find out. Usually, scientists ask a question after they’ve made a lot of observations. • An observation is any use of the senses to gather information. Measurements are observations that are made with instruments.
IS THAT A FACT ! • In 1864 and 1865, James Clerk Maxwell made observations about electricity and certain observations about magnetism and showed how the two phenomena are related. As a result of his investigations, he developed his theory of electromagnetism, one of the most important scientific advances of the nineteenth century.
SCIENCE HUMOR Q: Why is a science lesson like a worm in a cornfield? A: They both go in one ear and out the other.
MISCONCEPTION ALERT Just because a hypothesis is un-testable does not mean that it is wrong. It just means that there is no way to support or not support it. Scientists must always formulate hypotheses for which they can make observations and gather information.
Form a Hypothesis • Once you’ve asked your question, your next step is forming a hypothesis. A hypothesis is a possible explanation or answer to a question. You can use what you already know and any observations that you have made to form the hypothesis. A good hypothesis is testable. If no observations or information can be gathered or if no experiment can be designed to test the hypothesis, it is un-testable.
Before Scientists Test a Hypothesis • They often make a prediction that state what they think will happen during the actual test of the hypothesis. Scientists usually state predictions in an “ If…then…” format.
REVIEW • How do scientists and engineers use the scientific method? Scientists use the scientific method to answer questions and solve problems. Engineers can use the scientific method to create new technology.
REVIEW (cont) • Give three examples of technology from your everyday life. Sample answers: car engines, CD players, air-conditioning units, spoons, and doorknobs.
REVIEW (cont) 3. Analyzing Methods. Explain how the accuracy of your observations might affect how you develop a hypothesis. Sample answer: If observations or measurement are not accurate, they can affect how reasonable a hypothesis is. As a result, answering the question may be more difficult and take more time than if observations and measurements were accurate from the beginning.
Test the Hypothesis • After you form a hypothesis, you must test it to determine whether it is a reasonable answer to your question. In other words, testing helps you find out if your hypothesis is pointing you in the right direction or if it is way off the mark. Often a scientists will test a hypothesis by testing a prediction.
Test the Hypothesis (cont) • One way to test a hypothesis is to conduct a controlled experiment. In a controlled experiment, there is a control group and an experimental group. Both groups are the same except for one factor in the experimental group, called a variable. The experiment will then determine the effect of the variable.
Test the Hypothesis (cont) • Sometimes a controlled experiment is not possible. Stars, for example, are too far away to be used in an experiment. In such cases, you can test your hypothesis by making additional observations or by conducting research. If your investigation involves creating technology to solve a problem, you can make or build what you want to test and see if it does what you expected it to do.
DATA • Data are any pieces of information acquired through experimentation, observation and research.
Analyze the Results • After you collect and record your data, you must analyze them to determine whether the results of your test support the hypothesis. Sometimes doing calculations can help you learn more about your results. Organizing numerical data into tables and graphs make relationships between information easier to see.
Science Bloopers • Experiments don’t always turn out as expected. In 1856, William Henry Perkins was experimenting to synthesize the anti-malarial drug quinine from coal tar. He didn’t succeed, but he accidentally made aniline purple (mauve), the first synthetic dye. Mauve dye was used to color cotton, wool, and silk. Further experiments led to the development of many other dyes from coal tar.
Draw Conclusions • At the end of an investigation, you must draw a conclusion. You could conclude that your results supported your hypothesis, that your results did not support your hypothesis, or that you need more information. If you conclude that your results support your hypothesis, you can ask further questions. If you conclude that your results do not support your hypothesis, you should check your results or calculations for errors.
Draw Conclusions (cont) • You may have to modify your hypothesis or form a new one and conduct another investigation. If you find that your results neither support nor disprove you hypothesis, you may need to gather more information, test your hypothesis again, or redesign the procedure.
Communicate Results • One of the most important steps in any investigation is to communicate your results. You can write a scientific paper, make a presentation, or create a Web site. Telling others what you have learned is how science keeps going. Other scientists can conduct their own tests, modify your tests to learn something more specific, or study a new problem based on your results.
Breaking the Mold of the Scientific Method • Not all scientists use the same scientific method, nor do they always follow the same steps in the same order. Why not? Sometimes you may have a clear idea about the question you want to answer. Other times, you may have to revise your hypothesis and test it again. While you should always take accurate measurements and record data correctly, you don’t always have to follow the scientific method in a certain order.
Building Scientific Knowledge • Using the scientific method is a way to find answers to questions and solutions to problems. But you should understand that answers are very rarely final answers. As our understanding of science grows, our understanding of the world around us changes. New ideas and new experiments teach us new things.
Building Scientific Knowledge (cont) • Sometimes, however, an idea is supported again and again by many experiments and tests. When this happens, the idea can become a theory or even a law.
Scientific Theories • You’ve probably heard a detective on a TV show say, “I’ve got a theory about who committed a crime.” Does the detective have a scientific theory? Probably not; it might be just a guess. A scientific theory is more complex than a simple guess.
Scientific Theories (cont) • In science, a theory is a unifying explanation for a broad range of hypotheses and observations that have been supported by testing. A theory not only can explain an observation you’ve made but also can predict an observation you might make in the future. Keep in mind that theories can be changed or replaced as new observations are made or as new hypotheses are tested.
Scientific Laws • What do you think of when you hear the word law? Traffic laws? Federal laws? Well, scientific laws are not like these laws. Scientific laws are determined by nature, and you can’tbreak a scientific law!
Scientific Laws (cont) • In science, a law is a summary of many experimental results and observations. A law tells you how things work. Laws are not the same as theories because laws only tell you what happens, not why it happens. Although a law does not explain why something happens, the law tells you that you can expect the same thing to happen every time.
QUIZ 1. What is the relationship between an experiment and a hypothesis? 2. When following the scientific method, what is the correct procedure for investigation? 3. What is a variable?
Answers 1. An experiment is a test of a hypothesis to support or disprove it. 2. There is no correct order as long as steps are followed so that accurate measurements are made and data is recorded. 3. A factor that can be changed in an experiment to determine its effect on the outcome.
ASSESSMENT Are the following laws or theories: 1. An object that is dropped falls to the ground. 2. Gravitational forces causes an attraction between two objects. 3. The universe began with a very powerful explosion. 1. (law) 2. (law) 3. (theory)
What is a Model? • A model is a representation of an object or system. Models are used in science to describe or explain certain characteristics of things. Models can also be used for making predictions and explaining observations. A model is never exactly like the real object or system—if it were, it would no longer be a model. Models are particularly useful in physical science because many characteristics of matter and energy can be either hard to see or difficult to understand.
Models Help You Visualize Information • When you’re trying to learn about something that you can’t see or observe directly, a model can help you visualize it, or picture it in your mind. Familiar objects or ideas can help you understand something a little less familiar.
Models Build Scientific Knowledge • Models not only can represent scientific ideas and objects but also can be tools that you can use to conduct investigations and illustrate theories.
Models Can Save Time and Money • When creating technology, scientists often create a model first so that they can test its characteristics and improve its design before building the real thing.
Models Can Save Time and Money (cont) • Models allow you to test ideas without having to spend the time and money necessary to make the real thing.
REVIEW • What is the purpose of a model? 2. Give three examples of models that you see every day. 3. Interpreting Models.Both a globe and a flat world map model show certain features of the Earth. Give an example of when you would use a globe and an example of when you would use a flat map.
Answers 1. The purpose of a model is to represent concepts or characteristics of objects that are more difficult to see or hard to explain. 2. Acceptable answers include bus maps, and attendance record, a stuffed animal, assembly instructions for a bicycle, and sheet music. 3. Sample answers: A globe would be better if you wanted to compare the sizes of different countries; a flat map would be better if your wanted to carry a world map in you backpack.
Measurements and Safety in Physical Science • Hundreds of years ago, different countries used different systems of measurement. In England, the standard for an inch used to be three grains of barley placed end to end. Other standardized units of the modern English system, which is used in the United States, was based on parts of the body, such as the foot. Such units were not very accurate because they were based on objects that varied in size.
Measurements and Safety in Physical Science (cont) • Eventually people recognized that there was a need for a single measurement system that was simple and accurate. In the late 1700’s, the French Academy of Sciences began to develop a global measurement system, now known as the International System of Units, or SI.
The International System of Units • Today most scientists in almost all countries use the International System of Units. One advantage of using SI measurements is that it helps scientists share and compare their observations and results. Another advantage of SI is that all units are based on the number 10, which makes conversions from one unit to another easier to do. The table in the appendix of your book contains the commonly used SI for length, volume, mass, and temperature.
The International System of Units(Length) • How long is an Olympic-sized swimming pool? To describe its length, a physical scientist would use meters (m), the basic SI unit of length. Other SI units of length are larger or smaller than the meter by multiples of 10.
The International System of Units(Length) • For example, 1 kilometer (km) equals 1,000 meters. If you divide 1 m into 1,000 parts, each part equals 1 mm. This means that 1 mm is one-thousandth of a meter. Although that seems pretty small, some objects are so tiny that even smaller units must be used. To describe the length of a grain of salt, micrometers (um) or nanometers (nm) are used.
The International System of Units(Volume) • Imagine that you need to move some lenses to a laser laboratory. How many lenses will fit into a crate? That depends on the volume of the crate and the volume of each lens. Volume is the amount of space that something occupies.
The International System of Units(Volume) cont • Volumes of liquid are expressed in liters (L). Liters are based on the meter. A cubic meter (1 m3)is equal to 1,000 L. So 1,000 L will fit into a box 1 m on each side. A milliliter (mL) will fit into a box 1 cm on each side. So 1 mL = 1 cm3. Graduated cylinders are used to measure the volume of liquids.
The International System of Units(Volume) cont • Volumes of solid objects are expressed in cubic meters (m3). Volumes of smaller objects can be expressed with cubic centimeters (cm3) or cubic millimeters (mm3). To find the volume of a crate, or any other rectangular shape, multiply the length by the width by the height. To find the volume of an irregularly shaped object, measure how much liquid that object displaces.
