Section 1.2: Using a Scientific Approach

1. Section 1.2: Using a Scientific Approach What is the goal of the scientific method? How is a scientific law different from a scientific theory? Why are scientific models useful?

2. Scientific Method • The scientific method is an organized plan for gathering, organizing, and communicating information • The goal of scientific method is to solve a problem or better understand something • Have you ever heard of Edward Jenner? • Small pox epidemic-killed millions • He noticed milk maids didn’t get small pox • They already had cow pox • Injected people with cow pox (first vaccine)

3. Make Observation Ask Question Develop Hypothesis Revise Hypothesis Test Hypothesis with Experiment Test Hypothesis with More Experiments Analyze Data and Draw Conclusions Hypothesis Supported Hypothesis Not Supported Develop Theory

4. Observations • Most scientific investigations begin with an observation • Repeatable observations are known as facts • You can sometimes combine your observations into a question: • Does having cow pox keep you from getting small pox? • Does walking in the rain actually keep you drier?

5. Forming a Hypothesis • A hypothesis is a proposed answer to a scientific question • Many people confuse a hypothesis with a theory • Hypotheses have not yet been tested or results of testing are not yet conclusive • Theories have been tested and have lots of data to back them up • For a hypothesis to be useful, it must be testable • How would you test the hypothesis that walking in the rain actually keeps you drier than running?

6. Testing a Hypothesis • Scientists perform experiments to test their hypothesis • Any factor that can change is called a variable • What are some of the variables in the walking vs. running in the rain experiment? • Your hypothesis might state that your speed causes a change in the amount of water that hits you

8. Variables • The variable that you manipulate (change) is called the manipulated or independent variable (x-axis) • The variable that responds to those changes is called the responding or dependent variable (y-axis) • In a controlled experiment, a scientist will change or manipulate only one variable at a time • All other variables are kept constant or controlled.

9. QUESTIONS: • What was the independent or manipulated variable in the walking vs. running experiment? • What was the responding or dependent variable in the experiment? • What were some of the controlled variables the Myth Busters held constant in their experiment?

10. Drawing Conclusions • Scientists draw conclusions based on the data collected • Sometimes their conclusions support the original hypothesis • In this case, scientists will usually repeat the experiment with other variables taken into consideration • Other times the conclusions do not support the hypothesis • The scientist then has to revise the hypothesis or propose a new one and design a new experiment

11. Developing a Theory • When a hypothesis has been supported in repeated experiments, scientists can begin to develop a theory • A scientific theory is a well-tested explanation for a set of observations • Example: Kinetic Theory • Particles in motion; explains melting & pressure • Theories can’t really be proved • They become stronger as facts support them • They may be revised or replaced if new evidence or discoveries are made

12. QUESTIONS • Can you call something a theory just because one experiment supported your hypothesis? • Suppose you wanted to test how running affects your heart rate. • What would your hypothesis be? • How could you test your hypothesis? • What would be your variables?

13. Scientific Laws • A scientific law is a statement that summarizes a pattern found in nature • It describes the pattern but does not attempt to explain it • Example: Newton’s Law of Gravity • Two objects are attracted to each other by a gravitational force • Scientists still yet to agree on a theory that explains how gravity works

14. Scientific Models • A model is a representation of an object or event • Scientific models make it easier to understand things that may be difficult to observe directly • Can be physical like a model of the solar system • Mental models are used to explain phenomenon like what the composition of an atom • Model is believed as long as data supports it • If data doesn’t support the model, the model is replaced or revised, just like hypotheses • The fact that models are replaced means discoveries are being made

15. QUESTIONS: • How does a scientific law differ from a scientific theory? • Why are scientific models useful? • A model can take the form of a physical object or a concept. Give an example of each.

16. Creating A Model • What are some common scientific models you have seen or perhaps made? • Take turns sharing one or two examples • Your turn to make a model • Pick one of your teammate’s suggestions and create your own model • Catch: You can only use the tools I have supplied you and you can’t trade with anyone in the group– if you got the scissors, you do all the cutting, etc.

17. Safety • Safe procedures must be followed • Lots of dangers associated with lab work • Follow safety precautions at all times • Most important: Always follow your teacher’s instructions and the steps or instructions of the experiment • If you are in doubt about any step, ASK • You are responsible for your own safety, as well as the safety of your classmates

18. Homework • Answer Section 1.1 questions on pages 3-4 of your Reading and Study Workbook • You may have to find some of the answers in your textbook but most can be found on the study guide from class today