What are Your Students Really Thinking?

Using diagrams, white boards, and Socratic questioning to reveal your student’s innermost thoughts … about physics

Modeling PhysicsDavid Hestenes, Malcolm Wells, Greg Swackhamer, and 100’s of othersArizona State University http://modeling.asu.edu/

CASTLE (Capacitor Aided System for Teaching and Learning about Electricity)

Dr. Melvin Steinberg, Smith CollegeAvailable from PASCO, EM-8624A CASTLE Kit - PASCO scientific .

Extended Physics Community at UNC Greensboro, http://epc.uncg.edu

The Modeling Method of Physics Teaching

Recognized by the U.S. Department of Education

one of the seven best K-12 educational technology programs out of 134 programs evaluated (2000). one of two exemplary programs in science education (2001).

Why use whiteboards, diagrams and Socratic Questioning?

Symbolic Representations

Physical System

Mental Model

Verbal

Algebraic

Diagrammatic

Graphical

Unaware that their own ideas … differ drastically from those of the teacher, most students systematically misunderstand what they hear and read in traditional introductory physics.

Why is this so?• Before physics instruction, students hold naïve

beliefs about mechanics which are incompatible with Newtonian concepts in most respects.

• Such beliefs are a major determinant of student performance in introductory physics.

• These beliefs are strongly held and often unconscious.

• Students do not change their deeply held beliefs until they are conscious of those beliefs, are aware that those beliefs do not effectively explain the world, and have a viable alternative.

A Taxonomy of Naïve BeliefsA. Principles of motion

1. Description of motion:2. In the absence of forces, every object remains at rest (with respect to the earth).3. The causal principle of motion: Every motion has a cause.4. The greater mass exerts the greater force.5. the object which causes motion of the other exerts the greater force, because it overcomes the other’s opposition.6. Dominance: Motion is determined by the larger of two competing forces.7. Compromise: Motion is determined by a compromise among competing forces.

B. Influences on Motion1. Inertial Resistance2. A constant force produces a constant velocity3. Acceleration is due to increasing force.4. A constant force has a limited effect depending on its magnitude.5. long-range forces cannot act on an object in a vacuum.6. An Internal force (or impetus) maintains motion of an object7. Resistance opposes an applied force or consumes the impetus of a moving object.8. Obstacles may redirect or stop motion, but they cannot be agents of an applied force.9. Gravity is a tendency of objects to fall down, but is not a force.10. Heavier objects fall faster.

Research Backs up These Conclusions

• Multiple modes of expression appeal to each student’s strengths and give the teacher a more complete picture of what is happening inside student’s brains.

• Students learn more thoroughly by having to explain their own thoughts well enough for other students to understand.

• Diagrams and graph serve as a bridge between experiments, fundamental principles and specific equations.

• Students can develop their own equations using the structure provided by diagrams and graphs.

• Provides frequent opportunity for students to articulate, defend and test their own beliefs.

Advantages of Diagrams, Graphs and Socratic Approach

• Uses principles and equations developed in discovery-based labs.

• Encourages student creativity – more interesting for teacher

• Part of a learning cycle that truly changes student's beliefs

Advantages Re-inforced by other aspects of modeling

• takes time• takes a year-long investment to develop student skills• takes great teacher skill to lead students through confusion

and teach them how to think for themselves• more difficult and time consuming to plan lessons and

classes• Learning curve for teacher• Resistance from some students, colleagues, parents and

administrators

Disadvantages of Socratic Approach

• How to use pie charts, bar graphs, vector addition diagrams, circuit diagrams, and motion graphs and diagrams to promote understanding and develop equations.

• How to direct students through problem-solving Socratically without examples.

• Diagrams, graphs and Socratic questioning are more successful when combined with a full modeling cycle

• You want to work with other teachers to bring a modeling workshop to your district. (NCLB, funded through district, bring workshop to teachers)

What do I hope you will learn from this presentation?

The Modeling Approach to Energy

• Starts with the first law of thermodynamics.

• Energy storage and transfer are more fundamental concepts than potential energy, kinetic energy and work.

• There are not different forms of energy.

• Energy is the ability to cause change.

How can energy be stored? • In moving objects – kinetic energy

• In stretching objects – elastic potential energy• In gravitational fields – gravitational potential

energy• In hot objects – thermal energy • In electric fields– electrical potential energy• In chemical bonds – chemical potential energy• In electrons orbiting atoms – atomic energy• In the nucleus of an atom – nuclear energy

Energy Bar Graphs and System Schemas

Energy bar graphs and system schemas build on the conceptual foundation established by energy pie charts, but organize the information in a way that strongly suggests the conservation of energy equation.

Example: A person exerts a constant force on a box initially at rest on a horizontal, frictionless surface and pushes it for a distance of several meters. NOTE: consider that it starts from rest and is still being pushed even in the last pie.Draw a set of four energy pie charts for this situation.

Example: A person exerts a constant force on a box initially at rest on a horizontal, frictionless surface and pushes it for a

distance of several meters. NOTE: consider that it starts from rest and is still being pushed even in the last pie.

Echem

Echem

EK

Echem

EK

Echem

EK

Definition of “Force”

A push or pull

Energy exerted on an object.

Power exerted on an object.

Something that changes the motion of an object

A resistance.

Example: A person exerts a constant force on a box initially at rest on a horizontal, frictionless surface and pushes it for a

distance of several meters. NOTE: consider that it starts from rest and is still being pushed even in the last pie.

Echem

Echem

EK

Echem

EK

Echem

EK

Example: A person exerts a constant force on a box initially at rest on a horizontal, frictionless surface and pushes it for a

distance of several meters. NOTE: consider that it starts from rest and is still being pushed even in the last pie.

Beneath each pie chart, draw a bar graph representing the same information. Use one bar for each wedge of your pie.

Echem

Echem

EK

Echem

EK

Echem

EK

Example: A person exerts a constant force on a box initially at rest on a horizontal, frictionless surface and pushes it for a

distance of several meters. NOTE: consider that it starts from rest and is still being pushed even in the last pie.

Echem EchemEKEchemEK

EchemEK

Echem

Echem

EK

Echem

EK

Echem

EK

Echem EchemEKEchemEK

EchemEK

With bar graphs, we are concerned principally with the initial and final energy storage. So erase your middle two bar graphs and replace them with a system schema.

Example: A person exerts a constant force on a box initially at rest on a horizontal, frictionless surface and pushes it for a

distance of several meters. NOTE: consider that it starts from rest and is still being pushed even in the last pie.

Example: A person exerts a constant force on a box initially at rest on a horizontal, frictionless surface and pushes it for a

distance of several meters. NOTE: consider that it starts from rest and is still being pushed even in the last pie.

Echem

object

earth surface

person EchemEK

Example: A person exerts a constant force on a box initially at rest on a horizontal, frictionless surface and pushes it for a

distance of several meters. NOTE: consider that it starts from rest and is still being pushed even in the last pie.

Each line in a system schema represents an interaction between two objects, but only some of those interactions involve a transfer of energy. If energy is transferred, add an arrowhead to show which way the energy flows.

Echem

object

earth surface

person EchemEK

Example: A person exerts a constant force on a box initially at rest on a horizontal, frictionless surface and pushes it for a

distance of several meters. NOTE: consider that it starts from rest and is still being pushed even in the last pie.

Echem

object

earth surface

personEchemEK

working

Echem

Echem

EK

Echem

EK

Echem

EK

When a force causes a transfer of energy, that is called working.

Energy can also be transferred by conducting.

Etherm-metal Etherm-H2OEtherm-metal Etherm-H2O

metal

H2O

conducting

A piece of hot metal is dropped into a well-insulated glass of water.

Energy can also be transferred by radiating.

Uelec + KE = Eelectron

Ephoton

Uelec + KE = Eelectron

Ephotonphoton

electron

radiating

A photon of light interacts with an atom, causing its electron to jump up an energy level.

Each wire in an electric circuit is assigned a color according to the voltage in that wire.

Red = greatest voltage in the circuitOrange = next greatest

Green = next leastBlue = least voltage in the circuit.

Any wire or connected wires must have the same color code because wires have too little resistance to sustain a voltage difference.

All differences in voltage, and therefore differences in color must occur across devices such as batteries or light bulbs.

Color Coding Electric Circuits

Yellow = medium

The more rays drawn out of a light bulb, the brighter it is.

The more tails drawn on an arrow representing electric current, the greater the current.

Bulb Rays and Arrow Tails

Physics Education Research (PER) shows a real crisis in understanding

• What does it mean when students can readily solve the quantitative problem at left, yet not answer the conceptual question at right?

4

2

6

8 V

P

Q

A

B

C

S

For the circuit above, determine the current in the 4 resistor

and the potential difference between P and Q.

Bulbs A, B and C are identical. What happens to the brightness of bulbs A and B when switch S is closed?

PER shows conclusively that textbooks, lucid lectures and lots of repetitive problem-solving are not effective in remedying the situation.• Before physics instruction, students hold naïve beliefs about

mechanics which are incompatible with Newtonian concepts in most respects.

• Such beliefs are a major determinant of student performance in introductory physics.

• These beliefs are strongly held and often unconscious.  • Students do not change their deeply held beliefs until they

are conscious of those beliefs, are aware that those beliefs do not effectively explain the world, and have a viable alternative.

How do you change a mind?

• Become conscious of existing beliefs

• Be able to articulate and defend those beliefs

• Confront evidence that tests those beliefs

• Evaluate alternatives

• Learn to catch yourself slipping back into your pre-conceptions (cycling back to evidence)

Diagrams, graphs and Socratic questioning are components of an instructional method that produces better results.