Why can physics be difficult to learn…

and challenging to teach?

Phil Scott

Centre for Studies in Science and Mathematics Education, University of Leeds, UK.

Fysikermøtet 200511 - 14 August 2005   Rica Brakanes Hotel, Ulvik i Hardanger.

Physics: frightful but fun…

Angell, Guttersrud, Henriksen, Isnes (2004)Science Education

‘A general feature of physics pupils’ descriptions of their subject is that physics is regarded as difficult and with a high workload, but also interesting’.

‘All pupils (grade 12) agree to a great extent that physics is difficult’

‘From our data it appears that physics is different from other school subjects (notably English and social science) in that it has a higher workload and a faster progression and is more conceptually demanding’.

What is involved in learning physics?

Learning physics involves developing a new way of talking and thinking about the natural world: drawing on specific concepts, theories, laws, mathematical tools, conventions.

This is a way of talking and thinking which has been developed and validated by the scientific community

It is a way of talking and thinking which must be consistent with observations and measurements of the physical world.

What is involved in learning physics?

Everyday sociallanguage

(Spontaneous concepts)

…Vygotsky

Scientificsocial language

(Scientific concepts)

Why can learning physics be so:

DIFFICULT?!

Why does the ball fall?

Everyday view:

The ball falls because

you let go of it, and it’s

heavy.

Scientific, physics, view

The ball falls because of

the gravitational pull of

the Earth.

Falling Conceptual tools: not ‘heaviness’ of the object…

but the concept of ‘gravity’

Basic assumptions about the nature of the world (ontological demand): not a contact force…but action at a distance, ‘the pull of the Earth’

Nature of knowledge (epistemological demand):not a ‘one-off’…but a generalisable explanation: falling, tides, planetary orbits…

Learning physics

…involves developing a new way of talking and thinking about the natural world

…always occurs against a backdrop of everyday ways of talking and thinking

…everyday ways of thinking are referred to as ‘alternative conceptions’!

BIG and SMALL learning demands

Different areas of physics make different demands Where the learning demand is BIG physics can be

difficult to learn and tough to teach Where the learning demand is SMALL the physics

seems like ‘common sense’.

Leach and Scott (2002)Studies in Science EducationDesigning and evaluating science teaching sequences

Learning demand: between the particles

What lies between the air particles?

1. And what is in between those particles?

Researcher: And what is in between those particles?

Student: Hmm……..space?

Researcher: Tell me more about that.

Student: Well… there isn’t really space because everything’s made up of something. You can’t just have something exists. Everything has pieces to it so it probably couldn’t be space. It could be….smaller particles? Cos, there couldn’t be nothing…so there’s probably just ones that can move around. Smaller ones.

2. What is in that area between the particles?

Researcher: What is in that area between the particles?

Student: Erm….probably, as I said before…probably either smaller ones or…. erm….erm…energy?

Researcher: Smaller what?Student: Smaller particles.Researcher: And how are those particles different?Student: They’re probably from a different substance,

since air’s made up of different chemicals. Erm….the particles probably change…vary….. with the substance that it pertains to.

3. And what’s in between the smaller particles?

Researcher: And what’s in between the smaller particles?

Student: Well….it couldn’t be nothing. I could guess that there are probably smaller ones…. cos…erm….I’d love to say air but this is air. So…it would be….within air. You can’t have nothing. So you’d have the smaller pieces.

Researcher: And why can’t you have nothing?Student: Cos I don’t think that there is such a thing as

nothing. Because even air which most people think is nothing….is made up of nothing…is just space…empty space. It has pieces to it as well.

Learning about special relativity

Posner, Strike, Hewson and Gertzog (1982)Science Education

Learning occurs if a new idea is both

intelligibleand

plausible

‘One source of difficulty in learning special relativity stems from its lack of initial plausibility to physics students’.

How can two clocks read different times?

Student: I mean how could they (the clocks) change? Time only goes at one rate, right?

Student: Yeah, I mean, absolute time, it just seems to go on at a certain rate everywhere. It just seems natural that it’s constant everywhere. I mean, even though you see these results

Shrinking rods

Student: I see them as being – as changing their length, or changing their time. But I can’t talk to the person who’s moving at the same velocity as the stick and the clock. He’s telling me they don’t change…I feel they haven’t changed, but the way I’m looking at them has changed…I guess I’m allowing for the fact that the person who’s seeing things at rest, who has his clock at rest, his metre stick at rest, has [pause] a little more right to say what is really happening to the sticks.

Student: …the fact that it’s moving makes it appear to me as if it were foreshortened.

Feynman: on physics learning

…there is this possibility: after I tell you something, you just can’t believe it. You can’t accept it. You don’t like it.

It’s a problem that physicists have learned to deal with: they’ve learned to realise that whether they like a theory is not the essential question. Rather it is whether or not the theory gives predictions that agree with experiment.

The theory of QED describes nature as absurd from the point of view of common sense. And it agrees fully with experiment. So I hope you can accept Nature as she is…absurd.

Richard Feynman (1985)QED The strange theory of light and matter

Students’ everyday ideas

Air is weightless…or has negative weight Heat is a kind of substance Matter disappears during dissolving Particles (molecules) expand on heating Light travels further in the dark We see things through light leaving our eyes Energy gets used up A force is needed to sustain steady motion Things fall because they are heavy

Students’ alternative frameworks: Pfundt and Duit, 1991: Numbers of published papers.

Mechanics 281

Electricity 146

Heat 68

Optics 69

Particles 60

Energy 69

Astronomy 36

Modern physics 11

Chemistry 132

Biology 208

An approach to planning physics teaching

1. Identify the key physics concepts to be taught

2. Consider the nature of students’ existing thinking in this area

3. Analyse the differences between the physics way of knowing and the students’ existing thinking: specify the learning demand

4. Devise teaching approaches to address the learning demand.

Simple electric circuits

Year 7 pupils (age 11-12 years) No tuition in high school on electric circuits

Where does the ‘electricity’ come from?

Students’ thinking: ‘The electricity flows out of the battery when the circuit is complete’

Physics view: The electric charges originate in the circuit. When the circuit is completed the charges start flowing in all parts of the circuit simultaneously.

The learning demand

From point to point… the circuit is initially empty and fills with a

‘substance-like material’ that eventually reaches the bulb and causes it to light.

Students use a ‘linear causal’ pattern of reasoning

The learning demand

To all at once… When the circuit is completed the charges are

set in motion in all parts simultaneously Students need to use ‘cyclic causal’ reasoning in

which causes and effects co-occur.

Perkins and Grotzer (2005)

‘Dimensions of Causal Understanding’

Studies in Science Education

What to do about it?

The BIG circuit!

The ROPE loop analogy

Key questions

Battery

In this circuit, the bulb is lit.Read each of the statements below about what is happening in the battery. For each statement, put a tick in one box to show if you think it is correct or incorrect.

correct don’t know

incorrect

(a) Before the battery is connected, there are no electric charges in the wire. When the battery is connected, electric charges flow out of it into the wire.

(b) There are electric charges present in the battery and the wires all the time. The battery makes them move around the circuit.

(c) Chemical reactions in the battery make electric charge, which then flows round the circuit.

Institute of Physics: Supporting Physics Teaching 11-14

IOP sponsored to support non-specialists in teaching physics

at grades 7-9. to strengthen their confidence, understanding

and competence in physics teaching. CD ROM based

What do you need to know?

The physics ‘story’ Teaching and learning ‘challenges’

- pupil starting points

- the nature of the learning demand in different topic areas

Teaching approaches

- demos/practical activities

- analogies/explanations/anecdotes

Structure of the SPT materials

And Einstein…

A human being is a part of a whole, called by us ‘universe’, a part limited in time and space. He experiences himself, his thoughts and feelings as something separated from the rest... a kind of optical delusion of his consciousness. This delusion is a kind of prison for us, restricting us to our personal desires and to affection for a few persons nearest to us.

Our task must be to free ourselves from this prison by widening our circle of compassion to embrace all living creatures and the whole of nature in its beauty.

Physics learning

…as:

breaking free from

‘everyday thinking’…

Physics teaching

…as:

working the GAP between

‘everyday’ and

‘physics’ thinking