Big Idea 3: The Role of Theories, Laws, Hypotheses, and Models   The terms that describe examples of scientific knowledge, for example; theory, law, hypothesis, and model have very specific meanings and functions within science.

Benchmark Number & Descriptor SC.8.N.3.1 Select models useful in relating the results of their own investigations. SC.8.N.3.2 Explain why theories may be modified but are rarely discarded.

Understanding Results in Science

MODELS Models are developed in an effort to explain how things in nature work. Types of models Physical constructions Detailed pictures Equations and graphs

PHYSICAL CONSTRUCTIONS A scaled version of what is being investigated Real versions may be too small, big or dangerous to handle. Must contain the correct amount of details Too little – model is worthless Too much – model is complicated

DETAILED PICTURES Diagram that visually represents information helps: to organize facts to show relationships to analyze and interpret findings A Food Web in Terrestrial and Aquatic Ecosystem

EQUATIONS and GRAPHS Equations Graphs E = MC2 F = MA S = distance/time Mathematical expression of scientific theories Graphs Visual representation of data Show relationships between variables E = MC2 F = MA S = distance/time X axis = independent variable Y axis = dependent variable

Knowledge Check 1. Why do scientists use models? 2. List three types of models scientist use? 3. When using graphs, where are the variables located?

Knowledge Check 1. Why do scientists use models? To help explain and represent their findings 2. List three types of models scientist use? Physical constructions Detailed pictures Equations and graphs 3. When using graphs, where are the variables located? Independent = X-axis Dependent = Y-axis

A theory is created… After experiments have been completed and observations and conclusions have been made, a theory may be created. Set of ideas that link together many observations of the same experiment.

Development of a Simple Theory by the Scientific Method: Start with an observation that evokes a question: Broth spoils when I leave it out for a couple of days. Why? Using logic and previous knowledge, state a possible answer, called a hypothesis: Tiny organisms floating in the air must fall into the broth and start reproducing. Perform an experiment or test: After boiling some broth, I divide it into two containers, one covered and one not covered. I place them on the table for two days and see if one spoils. Only the uncovered broth spoiled. Then publish your findings in a peer-reviewed journal. Publication: "Only broth that is exposed to the air after two days tended to spoil. The covered specimen did not." Other scientists read about your experiment and try to duplicate it. Verification: Every scientist who tries your experiment comes up with the same results. So they try other methods to make sure your experiment was measuring what it was supposed to. Again, they get the same results every time. In time, and if experiments continue to support your hypothesis, it becomes a theory: Microorganisms from the air cause broth to spoil. http://wilstar.com/theories.htm

Is That Theory Your Final Answer… Theory has been confirmed over many independent experiments. Examples: Theory of Gravity Theory of Relativity Quantum Theory An experiment could show that a hypothesis is incorrect. A scientist is expected to propose a better theory to fill in that gap in our knowledge. Examples: The Earth is the center of the universe. Flat Earth Theory The classical elemental theory ACCEPTED THEORIES DISPROVEN THEORIES

Knowledge Check 1. What is a theory? 2. How might a theory be disproven? 3. List and explain a theory which still stands and one that has been disproven?

Knowledge Check 1. What is a theory? Set of ideas that link together many observations of the same experiment 2. How might a theory be disproven? New information or technology is applied to an existing theory, and the published results are not verified. 3. List and explain a theory which still stands and one that has been disproven? Theory = Theory of gravity (Every object in the universe attracts every other object in the universe) Disproven Theory = Geocentric theory (Earth is the center of the solar system.)