Key Ideas for These Lectures

Transcription

1 Ideas and Questions for Session 3 Charles (Andy) Anderson Key Ideas for These Lectures I. Nature of scientific reasoning II. Instructional representations III. Learning and inquiry cycles IV. Assessment Simplified Model of Scientific Reasoning Scientific inquiry: Constructing arguments from evidence Experiences (observations, data, events, phenomena, objects, systems) Patterns (graphs, charts generalizations, laws) Explanations (models, hypotheses theories) Scientific application: Using models to describe, explain, predict, design Scientific reasoning includes: a. Knowledge claims: experiences, patterns, explanations b. Practices that involve working with particular types of knowledge claims or making connections among knowledge claim: inquiry and application 1

2 General Teaching Strategies Covering content: Telling the story with examples and expecting students to tell it back Learning cycles focusing on application of model-based reasoning Inquiry cycles focusing on developing new models through reasoning about data Combined inquiry and learning cycles Questions to Answer 1. What will happen when the Alka-Seltzer drops into the water? 1. The bag will rise 2. The bag will not go up or down 3. The bag will sink 2. Why will that happen? 3. What predictions would you expect students to make, and why? Each Group of 4 Teachers Needs: 5 vials Cups of each color of solution Waste cup 4 droppers 4 soda straws 2

3 Key Questions about Colored Solutions 1. What stacks of solutions are possible? 2. Are any stacks impossible? 3. Is it possible to make different stacks by different techniques? a) In the vials, vs. droppers, vs. soda straws b) By using different amounts of liquid 4. Why? 5. How is this activity connected with the Alka-Seltzer demonstration? Comparing Student and Qualitative Scientific Ideas about Mass and Density Student ideas Objects and materials can be light or heavy Balance scales and floating/sinking both compare heaviness Qualitative scientific ideas Mass (extensive) is a property of objects Density (intensive) is a property of materials Balance scales compare mass Floating and sinking compare density Key Experiments to Help Students Prefer Qualitative Scientific Ideas Floating heavier substances on top of lighter ones (e.g., lots of red on top of a little green, glacier on top of a layer of water) Comparing different amounts of more and less dense substances Comparing equal amounts of more and less dense substances Quantitative scientific relationship: D = m/v 3

4 Scientific Qualitative Patterns and Explanations Qualitative pattern: less dense materials float in more dense materials Qualitative explanation: Why? One explanation Balance of forces Force = pressure x area Compare pressure on top and bottom of submerged object or fluid Scientific Quantitative Patterns: Archimedes Principle What is the size of the buoyant force? Buoyant force = weight of displaced fluid Buoyant force = density of displaced fluid x volume of object Weight of object = density of object x volume of object Three key variables II. Instructional Representations Instructional representations include the scientific reasoning of the teacher AND the students: a. Knowledge claims: experiences, patterns, explanations b. Practices that involve working with particular types of knowledge claims or making connections among knowledge claim 4

5 Instructional Representation for Buoyancy EPE Type Experiences Patterns Explanations (Observations, (Generalizations, (Theoretical Data) Laws) Models) Student Everyday Objects have two Personal experiences with general properties: floating and sinking heaviness and Impressions of amount weight Gases weigh less Comparing than liquids and amounts of liquids solids by pouring Heavier objects sink, light objects float Air does not make heavy objects float Scientific Systematic Weight/mass, Buoyant force is Qualitative observations of volume, and dens ity caused by floating and sinking, are separate difference in varying volume, properties pressure on the mass and dens ity of Whether objects or top and bottom of solids and liquids fluids float or sink an object (or part depends on relative of fluid) densities Scientific Measurements of Archimedes Pressure equals Quantitative weight and volume principle: Buoyant weight of fluid of different force equals volume above the point materials to of object times where it is calculate density density of medium. measured Measurements of (Weight equals weight of objects volume of object suspended in fluids times density of Measurements of object.) pressure at different depths in fluids 5