1. Table of Contents 2.4 How Does Scientific Knowledge Developed? Why Do Scientist use Models? What is a system? How are Models of Systems Used? Models as Tools in Science The World of Science

2. Vocabulary 2.4 1.Model- A representation of a complex object or process, used to help people understand a concept that they cannot observe directly. 2.System- A group or related parts that work together to perform a function or produce a result. 3.Input- Material, energy, or information that goes into a system 4.Process- A sequence of actions in a system. 5.Output- Material, energy, result, or product that comes out of a system. 6.Feedback- Output that changes a system or allows the system to adjust itself.

3. Why Do Scientist Use a Model? Pg.77 The word model has MANY meanings….. In science, a model is any representation of an object or process. For Example: Pictures, diagrams, computer programs, and mathematical equations are all examples of scientific models. Why scientist use models? In order to understand things they cannot observe directly. to represent things that are either very large or too small ex: Earth’s core an atom Other models, such as mathematical equations or word descriptions, are models of processes.

4. What is a System? Pg. 78 A system is a group of parts that work together to perform a function or produce a result. All systems have similar properties: Input Process Output Some systems also have feedback, output that changes the system in some way. Input is the material or energy that goes into a system. Process is what happens in a system Output is the material or energy that comes out of a system.

5. Models as Tools in Science pg.78/79 An Everyday System In a flashlight, many parts work together as a system. Share what you know to explain why a flashlight is a good example of a system.

6. How Are Models Of Systems Used? It’s easy to identify the inputs and outputs of a system. It’s not so easy to observe a system’s process. Use of Models: Scientists them to understand how systems work. Also to predict changes in a system as a result of feedback or input changes. Predictions based on models are uncertain. Droppler Radar System-

7. How Are Models Systems Used? Pg.80 When scientists construct a model of a system, they begin with certain assumptions (hypothesis). These assumptions allow them to make a basic model that accurately reflects the parts of the system and their relationships. Such as: A food chain is a good model of a simple system to begin to understand how energy moves through living things in an environment. However, it shows how only a few of those living things are related. Therefore, scientist may build a food web to model a more complete picture of the system.

8. A Basic Model In this model of a food chain in the Florida Everglades, the algae make food using the sun’s energy. Algae are tiny living things that make their own food. Models as Tools in Science

9. A Model of a Simple System This model of an Everglades food web contains overlapping food chains.

10. Modeling a Complex System pg. 82 Some systems that scientists study are complex. Many parts and many variables* interact in these systems. So scientists may use a computer to keep track of all the variables. Because such systems are difficult to model, scientists may model only the specific parts of the system they want to study. Their model may be used to show the processes in the system or to make predictions. *a variable is a factor that can be or is changed.

11. Models as Tools in Science How Arctic Sea Ice Melts The Arctic sea-ice system can be modeled by a diagram. What is the input, process, and output in this model?

12. Models as Tools in Science A Model of the Scientific Community The work of scientists can be modeled in a diagram. In which part of the diagram would you put each term? New Evidence, Design an experiment, make a model, ask questions, research information, explanations, theories and laws