Chapter 1 Section 3

Bell Ringer (Brainstorm)  To teach cardiopulmonary resuscitation, or CPR, instructors most often use a mannequin to model a human upper torso and head. Why do you think CPR is taught with a model instead of a real human? Explain your answer.

Today’s Objectives  Explain how models represent the natural world.  Identify three types of models used in science.  Describe theories and laws.

Alabama Course of Study  1 Identify steps within the scientific process.

Models in Science  Model- a representation of an object or system  Uses something familiar to help you understand something that is not familiar.  There are 3 common kinds of scientific models.  Physical  Mathematical  Conceptual

Physical Models  These help you see what it looks like  Does not show you how it interacts or works with other things

Turn and Talk  Why would someone use a physical model?  Why would studying a model not be as accurate as studying the real thing?

Mathematical Models  Made up of mathematical equations and data.  Some are simple (for example f=ma calculates force)  Some are so complex that only computers can handle them  These sometimes have variables  Sometimes, certain variables that no on thought of exist in a complex model. And a change in any of these variable could cause the model to fail.

 Name a possible limitation of a mathematical model.

 One possible limitation of a mathematical model is that complex models may have unknown variables. If the unknown variables are changed, a mathematical model could fail.

Conceptual Models  Some are systems of ideas  Others are based on making comparisons with familiar things to help illustrate or explain an idea  Example:  The Big Bang Theory  Describes how the planets and galaxies formed  Although it is widely accepted, astronomers have concluded that some data do not fit the model.  So, conceptual models may not take certain data into account. Or the models may rely on certain ideas but not on others.

Models: The Right Size  Models are used to represent things that are very small or very large.  Sometimes, models are used to learn about things you cannot see.  For example: sound waves cannot be seen but shown by using a slinky

Scientific Theories  Models are often used to help illustrate and explain theories.  Theory- an explanation for many hypotheses and observations  Supported by repeated tests  Can be used to predict what might happen in the future

 Scientists use models to help guide their search for new information.  This information can help support a theory or can show that the theory is wrong.  Models can be changed or replaced over time.

 What two things can a theory explain?

 A theory can explain a hypothesis or an observation.

Scientific Laws  What happens when a model correctly predicts the results of many different experiments?  Scientific law- summary of many experimental results and observations  Tells us how things work  Not the same as theories  Tell you only what happens, not why  Gravity is a scientific law.

Summary  A model uses familiar things to describe unfamiliar things.  Physical, mathematical, and conceptual models are commonly used in science.  A scientific theory is an explanation for many hypotheses and observations.  A scientific law summarizes experimental results and observations. It describes what happens but not why.

Exit Slip  1. In your own words, write a definition for the term model.  2. Which kind of model would you use to represent a human heart?  A. a mathematical model  B. a physical model  C. a conceptual model  D. a natural model  3. Explain the difference between a theory and a law.