Scientific Method

Scientific Method Lesson 1.03

Introduction • How do you tackle every day problems that occur in your life?

Objectives After completing this lesson, you will be able to: • Compare and contrast theories and laws. • Describe the systematic (step-by-step) process used by the scientific community. • Explain how scientific knowledge grows and evolves (changes).

The Scientific Method • a procedure for investigating questions and testing ideas that can be broken down into a series of steps. • ensure that scientists around the world are using similar procedures to make observations and discoveries. **We need these scientific methods in order to make comparisons, to test the validity of discoveries, and to have trustworthy results**

The Steps of the Scientific Method There are several versions, but the important thing is that all scientific methods are based on: • Rational thinking • Inquiry (seeking truth, information, or knowledge) • Experimentation

The Steps of the Scientific Method • Purpose • Research • Hypothesis • Experiment • Analysis • Conclusion

Step 1~ The Purpose • The Purpose is what you are trying to find out. It's based on observations. Often it is a questionthat you have about something you’ve observed. • Example- Let’s say you mow and maintain lawns in your neighborhood for a summer job. One of your customers has a healthy front lawn except for one spot where grass won’t grow. Your question might be “What is different about this spot that prevents the grass from growing?”

Step 2~ Research • Science is a body of knowledge. It is important that you research what other scientists have observed and discovered before you. Someone may have already tested your observation or something related to it. Example-To investigate the dead spot in the lawn, you might want to research at the library, local garden center, or on the internet for some reasons why grass might not grow. It is important to check several reliable sources!

Step 3~ Hypothesis • After researching what other scientists already know about your observation or question, you will need to come up with a prediction for what you think will happen. • A hypothesis is sometimes called an “educated guess” because you are making a prediction about how your question will be answered based on the research that you have done. • Forming a hypothesis involves an understanding of current scientific knowledge and creativity to look at the problem or question in a different way.

Example of a Hypothesis • The research you did about the dead grass led you to test the pH (acidity or basicity) of that spot compared to the rest of the lawn. • Seeing that the pH is higher, you might form the hypothesis “The higher pH of the soil prevents the grass from growing.”

Step Four~ Experiment Design and carry out a test to give you the answer to your original question or observation. • On a lab report we would write the experiment down step by step and call it the procedure. This procedure needs to be detailed enough so scientists around the world could conduct the same experiment and see if they get the same results. • Keep detailed records of all observations and data from your experiment. • In science, it is just as important to find out if your hypothesis was “wrong” as it is to find out if it was “correct”.

Example of an Experiment • To test if the pH of the soil is preventing the grass from growing, you may plant grass seed (the same type of grass as in the lawn) in several different pots. You can make the pH in each pot different by adding different amounts of calcium oxide (lime) to each pot. • It’s important to understand all of the variables of your experiment.

What is a Variable? • A variable is any factor or condition that can exist in differing amounts or types… or something that varies or changes. • An experiment usually has three kinds of variables: independent, dependent, and controlled. • Scientists use an experiment to search for relationships in nature and answers to test their hypothesis. • In other words, they design an experiment to test if a change in one quantity or factor will affect another factor in the way their hypothesis predicted.

Independent Variables • The independent variable is the one that the scientist has chosen to change within the experiment in order to test the hypothesis. A good experiment should only have one variable tested, or varied, so that the scientist can be confident that the observations made are a result of the changes made to the independent variable. HINT: Independent is what I Change! • Example- In the example experiment, the pH of the soil is the independent variable. This is the variable that you are testing. This is done by adding different amounts of calcium oxide (lime) to each pot.

Dependent Variables • The scientist will observe what happens to the dependent variable over the course of the experiment to see how it responds to the change made to the independent variable. • The observations made and data collected regarding the dependent variable are caused by, and depend on, the changes made to the independent variable. HINT:Dependent is my Data! • Example- In the example experiment, grass growth is the dependent variable. Any changes in grass growth are dependent upon the changes made to the independent variable–pH levels of the soil sets.

Controlled Variables • Experiments also have controlled variables. Controlled variables are the factors that a scientist chooses to keep constantover the course of the experiment in order to make sure that anything that happens to the dependent variable is caused only by the independent variable. • Example - In the example experiment, factors like temperature, water, and exposure to sunlight must be kept constant (controlled variables) between all the sets of soil in order to make sure that any changes to grass growth (dependent variable) are actually caused by the changes to the pH of the soil (independent variable)

Step 5~ Analysis • Analyze the data from your experiment. Compare your results. • You may need to compare your results to previous experiments. • You should always repeat your experiment to be sure you get the same results. • In order to be reliable, the results must be reproducible by you or by another scientist following the same procedure. • Example - Based on the results of your experiment, you can determine if the high pH of the soil may be what is preventing the patch of grass from growing.

Step 6~ Conclusion • Based on your analysis and comparisons was your hypothesis supported or not supported? • Sometimes this is very simple and your conclusion is obvious. On occasion, finding that your hypothesis isn’t supported will lead you to discover additional information or facts. From this conclusion, you may need to do more research or form a new hypothesis and experiment.

Example of Conclusions • If the experiment results show that the low pH is preventing grass growth, you can investigate safe ways to raise the pH of the soil. • If changing the pH does not seem to help the grass growth, you may need to go back to your research and form a different hypothesis.

Let’s Practice! Label These Steps! • Based on the data recorded, as well as any other observations made, determine whether the hypothesis was correct/supported. • If I grow plants under green light they will grow faster than under red light, because plants are green. • What color light helps plants grow fastest? • Plant seeds of the same type of plant keeping everything the same except that one set is in natural light, one in red light, and one in green light. • Based on what other scientists have done, it seems that red and green lights work well for plants. • Record the height of the plants every day for several weeks and compare the results.

Check your Answers • What color light helps plants grow fastest? (Purpose~C) • Based on what other scientists have done, it seems that red and green lights work well for plants. (Research~E) • If I grow plants under green light they will grow faster than under red light, because plants are green. (Hypothesis~B) • Plant seeds of the same type of plant keeping everything the same except that one set is in natural light, one in red light, and one in green light. (Experiment~D) • Record the height of the plants every day for several weeks and compare the results. (Analysis~F) • Based on the data recorded, as well as any other observations made, determine whether the hypothesis was correct/supported. (Conclusion~A)

Applying the Scientific Method • Scientific knowledge is constantly changing and developing because new observations or predictions are made every day. • The body of knowledge is examined and re-examined, using the steps of the scientific method. • It is important that scientists share their investigations and conclusions with others so it can be tested and used by scientists all over the world.

Famous Examples Did you know that people used to believe that decaying meat turned into maggots and flies? • In 1668 Francesco Redi decided to investigate • He set up several jars with meat: one set of jars was covered with fine gauze that allowed in air but no insects, and the other set of jars was left unsealed. • Rediobserved that flies flew in and out of the open jars but could not enter the jars covered in gauze.

Famous Examples Continued • After several days he saw that maggots appeared on the meat in the unsealed jars but no maggots appeared in the jars covered with gauze. This started a series of experiments by other scientists that disproved the idea of spontaneous generation. • This is a no longer supported theory that organisms can come from from inanimate or non-living matter.

Famous Examples Continued Did you know that Aristotle (who lived from 384 to 322 BC) believed that the Earth was the center of the universe and that the sun, moon, planets, and all the stars revolved around the Earth? • The Earth-centered view of the universe was widely accepted for about 1500 years. • It was not seriously challenged until the early 1600’s when scientists developed telescopes that helped them study the movement of planets and moons.

Theory or Law? What is the difference between a theory and a law? • Let’s look at somesimilaritiesfirst: • both developed using the scientific method • developed, tested, and changed over time So how are theydifferent?

Theory or Law? • The difference is that scientific theories describe why things happen and scientific laws present what does and will happen without explaining why. • HINT: The word Theory ends in the letter Y and it explains WHY

Theories • A theory is a set of ideas that tries to explain why things happen the way they do in the natural world. • A theory is a culmination of many scientific investigations that have been tested and proven to be true over time. • The information for theories is supported by the investigations of various scientists with different points of view. This is important because different points of view help us to test an idea more thoroughly in order to discover more information. • Sometimes we learn new things because we have new technology or make new discoveries. When this happens, we might change our theory. Theories are always changing. However, theories never become laws.

Examples of Theories Big Bang Theory • a theory about the origin of the universe • Scientific evidence suggests that our universe is ever-expanding from a hot and dense initial state. • Some evidence that supports this theory is cosmic microwave background radiation that is uniform throughout the universe. • This supports the notion that the gas which emitted this radiation long ago was very uniformly distributed. Scientists have attempted to conduct experiments to test the initial conditions of the Big Bang Theory. These experiments have provided some support of the expansion of the universe, but have been unable to provide evidence associated with the initial conditions of the universe. The Big Bang is considered a theory because it uses evidence, based on the scientific method, in an attempt to explain the origin of the universe.

Examples of Theories Atomic Theory • In this course, we will see how the scientific method was used over time to help scientists develop an understanding of atoms and how they make up all types of matter. • The atomic theory describes a model of atoms that explains why they behave the way they do and have the properties that they have.

Examples of Theories Theory of Evolution • The molecular clock hypothesis is still debated within the scientific community. • This hypothesis attempts to use the relationship between amino acids in the DNA of various species to estimate how long ago the various organisms diverged evolutionarily, from one another. • It appears that some DNA mutations (a change in the genetic structure of DNA), or evolutionary changes, occur in a clock-like fashion, over long periods of time. • If the mutation rate of a given gene is reliable, that gene can be used as a molecular clock. • This hypothesis is used as support for the theory of evolution because it attempts to explain how and when species mutated and evolved. The molecular clock hypothesis was developed using the scientific method and is still being evaluated and investigated by scientists today.

Scientific Laws • Laws are also based on what we observe and have learned from scientific experiments. Laws tell us about what happens in nature but do not attempt to explain why things happen. • Laws are developed when observations of the world around us are tested again and again by the scientific method until there is a consensus among scientists that the observation, often in the form of a mathematical equation, is reliable. A scientific law continues to be reevaluated whenever new observations are made to make sure the law is consistent with the new observations. • Theories attempt to explain why something happens, where laws just give detailed accounts of what does and will happen. Laws will never become theories and theories do not become laws.

Examples of Laws Law of Gravity • The law of gravity tells us that there is a force of attraction between two objects. This is a law because it describes the attraction in mathematical terms, but it does not attempt to explain why the force exists. Kepler’s Laws of Planetary Motion • There are three mathematical laws that describe the motion of planets in the solar system, called Kepler’s laws of planetary motion. These laws describe the motion of the planets in our solar system but do not explain why the planets follow these laws.

Review

TA DA!! Congratulations! You should now be able to: • Compare and contrast theories and laws. • Describe the systematic process used by the scientific community. • Explain how scientific knowledge grows and evolves. If you are struggling with these concepts, please review this lesson again.

Scientific Method